1991 MICHIGAN POTATO RESEARCH REPORT Volume 23 Michigan State University Agricultural Experiment Station In Cooperation With The Michigan Potato Industry Commission THE MICHIGAN POTATO INDUSTRY COMMISSION February 20,1992 To All Michigan Potato Growers & Shippers: The Michigan Potato Industry Commission, Michigan State University's Agricultural Experiment Station and Cooperative Extension Service are pleased to provide you with a copy of the results from the 1991 potato research projects. This years report is dedicated to the memory of Ronald Allen Andersen, and funded through a donation from the Andersen families. Ron's presence in the potato industry is greatly missed. His interest in the financial responsibility of the potato industry was demonstrated repeatedly in all the projects he became involved in throughout his career. This report includes research projects funded by the Michigan Potato Industry Commission as well as projects funded through the USDA Special Grant and other sources. Providing research funding and direction to principal investigators at MSU is a function of the Michigan Potato Industry Commission’s Research Committee, on behalf of the MPIC and potato growers of Michigan. Best Wishes for a prosperous '92 season, The Michigan Potato Industry Commission THE MICHIGAN POTATO INDUSTRY COMMISSION • 13109 SCHAVEY RD., STE. 7 • DEWITT, Ml 48820 • (517)669-8377 TABLE OF CONTENTS Page INTRODUCTION AND ACKNOWLEDGEMENTS, WEATHER AND GENERAL MANAGEMENT........... 1 MICHIGAN STATE UNIVERSITY POTATO BREEDING PROGRAM David S. Douches........................................................... 4 1991 POTATO VARIETY EVALUATIONS R.W. Chase, D.S. Douches, J. Cash, R. Hanunerschmidt, K. Jastrzebski, R. Leep and R.B. Kitchen.................................. 7 1991 POTATO SCAB RESEARCH R. Hanunerschmidt, D. Douches, K. Jastrzebski and C. Wallace............. 22 MANAGEMENT PROFILE OF STEUBEN R.W. Chase, R.B. Kitchen and K. Jastrzebski.............................. 26 EFFECTS OF NITROGEN FERTILIZER MANAGEMENT ON NITRATE LEACHING J.T. Ritchie and E. Martin............................................. 28 NITROGEN MANAGEMENT TO IMPROVE POTATO YIELD, QUALITY, AND GROUNDWATER QUALITY M.L. Vitosh, R.H. Leep and G.H. Silva.................................... 37 UNDERSTANDING THE RESPONSE OF POTATOES TO PHOSPHORUS Darryl D. Warncke and William B. Evans................................... 55 COLORADO POTATO BEETLE MANAGEMENT Ed Grafius, Beth Bishop, Walter Boylan-Pett, Judith Sirota and Kaja Brix..............................................................65 1991 NEMATOLOGY REPORT F. Warner, G.W. Bird, J. Davenport, C. Chen and B. Mather............... 78 POTATO STORAGE MANAGEMENT: ATLANTIC vs. SNOWDEN Roger Brook, Robert Fick and Ray Hanunerschmidt........................... 87 PACKAGING ALTERNATIVES FOR LIGHT USERS OF TABLESTOCK POTATOES Mary D. Zehner..........................................................91 1991 MSU POTATO RESEARCH REPORT R.W. Chase, Coordinator Introduction and Acknowledgements The 1991 Potato Research Report contains reports of potato research projects conducted by MSU potato researchers at several different locations. The 1991 report is the 23rd report which has been prepared annually since 1969. This volume includes research projects funded by the Special Federal Grant 88-34141-3372, the Michigan Potato Industry Commission and numerous other sources. The principal source of funding for each project has been noted at the beginning of each report. We wish to acknowledge the excellent cooperation of the Michigan potato industry and the MPIC for their continued support of the MSU potato research program. We also want to acknowledge the significant impact that the funds from the Special Federal Grant have had on the scope and magnitude of several research areas. Many other contributions to MSU potato research have been made in the form of fertilizers, pesticides, seed, supplies and monetary grants. We also acknowledge the tremendous cooperation of individual producers who cooperate with the numerous on-farm projects. It is this dedicated support and cooperation that makes for a productive research program for the betterment of the Michigan potato industry. We further acknowledge the professionalism of the MPIC Research Committee. The Michigan potato industry should be proud of the dedication of this Committee and the keen interest they take in determining the needs and direction of Michigan's potato research. A special acknowledgement goes to Richard Kitchen who retired from MSU in September of 1991 after completing a career of 39 years. Dick has been a cornerstone of the MSU potato breeding project, the development of the Montcalm Research Farm and the total MSU potato research program. His expertise, experience, assistance and advice has helped many, many faculty, students, colleagues and farmers over the years. Thanks go to Dick Crawford, for the day-to-day operations at the Research Farm and Dr. Kazimierz Jastrzebski, visiting scientist from Poland. Also, a special thanks to Jodie Schonfelder for the typing and preparation of this report. Weather The 1991 growing season can be best characterized as being very "quick". Heat units accumulated much more rapidly than in average years with the season being 2-3 weeks ahead of normal. Monthly average maximum and minimum temperatures were warmer than the 15 year average. There were only two days that the temperature exceeded 90° and night temperatures were generally cool and favorable for good growth and solids. The rapid growing season was also favorable for hollow heart development and was noted in several varieties. Rainfall was below the 15 year average for August and September which contributed to blackspot injury because of dry soil conditions at harvest. Soil Tests Soil tests for the general plot area were: pH 6.1 P2O5 449 k2o 219 Ca 800 Mg 152 Cation Exchange Capacity 5.3 me/100 g Previous Crops and Fertilizers The general plot area was planted to drilled soybeans in 1990 which were disked in the fall and seeded to winter rye all 1 1/2 bushels/A. In November of 1990, Vapam at 50 gpa was knifed into the plot area. Except in the fertilizer trials, where the amounts of fertilizers used are specified in the individual project reports, the following fertilizers were used in the potato trials: plowdown 0-0-50 300 lbs/A banded at planting 20-10-10 200 lbs/A broadcast at emergence 34-0-0 200 lbs/A sidedress at hilling 46-0-0 100 lbs/A through irrigation 28-0-0 120 lbs/A second application on russets 28-0-0 120 lbs/A Herbicides and Hilling A tank mix of metolachlor (Dual) at 2 lbs/A plus metrabuzin (Lexone) at 1/2 lb/A was applied preemergence. Hilling was completed when plants were 10-12” tall. Irrigation Irrigation was initiated on June 20 and eight applications were made during the growing season with the last application on September 6, 1991. Approximately 6” of irrigation water were applied. The MSU Irrigation Scheduling program was monitored by Don Smucker, Montcalm County Extension Director and these data were used to determine the timing for irrigation applications. Insect and Disease Control Thimet was applied at planting at 11.3 ounces/1,000 ft. of row. Foliar insecticide applications were initiated on May 29 for control of Colorado potato beetles which was the major insect problem throughout the season. Insecticides used were Imidan + PBO, Furadan, Cygon, Rotacide, Monitor and Kryocide. Fungicides used were Mancozeb and Pencozeb. The foliage fungicide application was initiated on July 2 which was determined by the MSU Potato Blight Forecaster Program. Table 1. The 15 year summary of average maximum and minimum temperatures during the growing season at the Montcalm Research Farm. April Max Year 62 1977 50 1978 50 1979 49 1980 1981 56 53 1982 1983 47 1984 54 58 1985 1986 60 61 1987 1988 52 56 1989 NA 1990 1991 60 15-YR. AVG. 55 April May May Min 37 31 33 31 35 28 28 34 38 36 36 31 32 NA 40 34 Max 80 67 66 69 64 72 60 60 70 70 77 74 72 64 71 69 Min 47 45 44 42 39 46 38 39 44 46 46 46 34 43 47 43 June Max 76 78 74 73 73 70 76 77 71 77 80 82 81 77 82 76 June Min 50 50 55 50 50 44 49 54 46 50 56 53 53 55 59 52 July Min JulyMax 85 81 82 81 77 80 85 78 81 82 86 88 83 79 81 82 61 56 57 58 51 53 57 53 55 59 63 60 59 58 60 57 August September September 6-Month 6-Month Average Average Max August Min 52 57 55 58 53 48 57 55 54 51 58 61 55 57 57 55 77 82 77 81 78 76 82 83 75 77 77 84 79 78 80 79 Max 70 75 76 70 67 66 70 69 70 72 72 71 71 72 69 71 Min 53 52 47 49 47 44 46 45 50 50 52 49 44 47 47 48 Max 75 72 71 71 69 70 70 70 71 73 76 75 74 NA 74 72 Min 50 49 49 48 46 44 46 47 48 49 52 50 46 NA 52 48 Table 2. The 15 year summary of precipitation (inches per month) recorded during the growing season at the Montcalm Research Farm. Year April May June July August September Total 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 15-YR. AVG. 1.65 2.34 2.58 3.53 4.19 1.43 3.47 2.78 3.63 2.24 1.82 1.82 2.43 1.87 4.76 2.70 0.46 1.35 1.68 1.65 3.52 3.53 4.46 5.14 1.94 4.22 1.94 0.52 2.68 4.65 3.68 2.76 1.66 2.55 3.77 4.37 3.44 5.69 1.19 2.93 2.78 3.20 0.84 0.56 4.85 3.53 4.03 3.03 2.39 1.89 1.09 2.64 1.23 5.53 2.44 3.76 2.58 2.36 1.85 2.44 0.82 3.76 5.73 2.70 2.61 5.90 3.69 3.21 3.48 1.96 2.21 1.97 4.72 2.10 9.78 3.44 5.52 4.06 1.75 3.76 8.62 2.77 0.04 6.59 3.82 3.24 5.34 3.90 3.30 18.60 3.32 5.36 1.33 3.64 1.50 4.76 17.39 16.80 12.85 21.99 19.68 21.38 19.11 20.48 18.95 32.72 19.55 14.14 17.62 21.51 21.45 19.71 Funding Federal Grant/MPIC/SFA/NPC MICHIGAN STATE UNIVERSITY POTATO BREEDING PROGRAM David S. Douches Department of Crop and Soil Sciences Cooperators: K. Jastrzebski, R. Freyre, R.W. Chase, R. Hammerschmidt, D. Maas, J. Cash and G. Bird To have a successful on-going potato breeding program the efforts must be divided into three integrated directions: 1) breeding and varietal development, 2) germplasm enhancement, and 3) genetics studies to understand the inheritance of key traits. The breeding goals at MSU are based upon current and future needs of the Michigan potato industry. Traits of importance include yield potential, disease resistance (scab and early die), chipping and cooking quality, storability, along with shape, internal quality and appearance. I. Varietal Development During the 1991 winter approximately 50 potato varieties and advanced breeding lines were chosen as parents for the greenhouse crossing block to generate new Fl seedling families for variety development. These parents were chosen on the basis of yield potential, specific gravity, disease resistance, processing ability, adaptation, lack of internal and external defects, etc. Over 200 cross combinations were made with the intention of combining traits from different clones to develop improved varieties. In the fall, approximately 650 single-hill selections were made from a total of 20,000 seedlings grown at the Montcalm Research Farm. Following harvest, specific gravity has been measured and chip-processing (from 45F storage) will be done during winter. These selections will be advanced to 4-hill plots in 1992 for further evaluation. Fifty-five 4-hill, eleven 20-hill, and 19 2x20-hill selections were also selected then post-harvest tested (specific gravity, 50 and 45F chip-processing and dormancy). The best 10 2x20 selections will be tested in a replicated trial at the Montcalm Research Farm in 1992 for more intensive evaluations. II. Germplasm enhancement We have also developed a "diploid" breeding program in an effort to simplify the genetic system in potato and exploit more efficient selection of desirable traits. In general, diploid breeding utilizes haploids of cultivated species and diploid wild and cultivated tuber-bearing relatives of the potato. These represent a large source of valuable germplasm, which can broaden the genetic base of the cultivated potato and also provide specific desirable traits such as tuber dry matter content, cold chipping and dormancy, along with resistance to disease, insects, and virus. Even though these potatoes have only half the chromosomes of the varieties in the U.S., we can cross these potatoes to transfer the desirable genes by exploiting 2n pollen. The diploid breeding program at MSU is a synthesis of five species: fi. tuberosum (adaptation, tuber appearance), S. phureja (cold-chipping, specific gravity), S. tarijense and berthaultii (tuber appearance, insect resistance) and S. chaconese (specific gravity, low sugars, dormancy). From an initial population of 3,500 seedlings from 62 crosses, 80 diploid selections have been made. Selection criteria was based upon tuber appearance, size, dormancy, and internal quality, along with maturity, specific gravity, and chip quality. These selections will be further crossed to improve their agronomic characteristics. III. Assessment of Potato Breeding Progress in the U.S. Replicated field trials were conducted at Montcalm, Michigan in 1990 and 1991 to compare 21 potato varieties that have or have had importance over the past century. The varieties were evaluated for total yield, marketable yield, maturity, internal defects, specific gravity, chip-processing quality, visual merit, tuber dormancy and scab resistance. A number of trends were observed over the two years. The many of the older varieties have a greater yield potential; however, the more recent varieties have improved appearance. The round white varieties have been improved for chip-processing ability and specific gravity. The long type varieties have shown an increase in the percent U.S. #1 yield. This study will help us develop breeding strategies to improve potatoes for Michigan. IV. Use of Molecular Markers for the Study and Analyses of Quantitative Trait Loci in Diploid Potato The objective of this study is to identify associations between molecular markers (isozymes and RFLPs) and quantitative trait variation for specific gravity and tuber dormancy in diploid potatoes. The identification of these linkages will make it more efficient to breed in the traits from the diploid breeding program. The populations used, named TRP132 and TRP133, are derived from two (tbr-chc x phu) crosses, have the female parent in common, and have 143 and 110 individuals respectively. In 1990 the two populations were planted with three locations at two locations in Michigan. After harvest, they were evaluated for the tuber traits and characterized with 11 isozyme loci. Single factor ANOVAs were conducted for each pairwise combination of quantitative trait and isozyme locus. For specific gravity, significant differences were found for 6-Pgdh-3, Got-2 and Pgm-1 for TRP133, and results were consistent in both locations. For dormancy, differences were found for 6-Pgdh-3, Got-1, Got-2 and Prx-3. In TRP132, differences were found for specific gravity for 6-Pgdh-3 and Got-2 over both locations, and for Pgm-1 and Dia-2 on only one location. In 1991 the populations were planted in one location with two replications, and then evaluated for specific gravity. Results have been analyzed for TRP133, showing high correlation with data from the previous year. Confirming previous results, significant association for this trait was found with 6-Pgdh-3 and Got- 2. Concurrently, RFLP analysis was initiated in the population TRP133. Up to date, thirty six tomato probes have been used, finding backcross, F2 and triallelic-type segregation patterns. Twenty of these probes have been scored, and analyzed for a total of 27 loci. Two probes have shown significant association with specific gravity, but their chromosomal location can still not be identified. Other four probes have shown significant association with dormancy. Linkage analysis indicates putative QTLs for this trait in chromosomes 2, 5, 7 and 8. Future plans include further survey of the genome with other probes to identify more QTLs and also fine-map those already identified. Also, progenies derived from 4x-2x crosses and segregating for some of the markers that show significant association with the QTLs will be studied. V. Evaluation of 4x progeny In a 2x x 4x cross. A 2x x 4x cross was made between NDD277-2 (4x breeding line) and T4182, a haploid from W231 that has been identified to produce mixed modes of 2n eggs. Using an electrophoretic marker that is closely linked to the centromere, half- tetrad analysis was applied to discriminate between FDR- and SDR-derived 4x progeny. A field study was conducted in Montcalm, Michigan to compare the field performance of the parents and the two subsets of the progeny. Based upon family means, there was no difference between the total tuber yield in the FDR and SDR progeny, however, the 4x parent had a significantly higher yield than either 4x progeny subset. Meanwhile, the haploid parent had significantly lower yield than the 4x progeny and the 4x parent. No differences were seen between the FDR- and SDR-subpopulations for the distribution of specific gravity and total tuber yield (on a single hill basis) . The level of inbreeding in the haploid parent may have nullified any differences we expected between the FDR- and SDR-derived progeny. Funding Fed. Grant/MPIC 1991 POTATO VARIETY EVALUATIONS R.W. Chase, D.S. Douches, J. Cash, R. Hammerschmidt K. Jastrzebski, R. Leep and R.B. Kitchen Departments of Crop and Soil Sciences Food Science, and Botany and Plant Pathology Michigan State University East Lansing, MI 48824 The objectives of the evaluation and the management studies are to identify superior varieties for fresh market or for processing and to develop recommendations for the growers of those varieties. The varieties were compared in groups according to the tuber type and skin color and to the advancement in selection. The most promising varieties are tested in management profile studies for their reaction to the spacing and nitrogen fertilization. Total and marketable yields, specific gravity, tuber appearance, incidence of external and internal defects, chip color, consistency and after cooking darkening as well as susceptibilities to common scab and bruising were determined. Before testing for chip color, the varieties were stored at 45 and 50°F. The field experiments were conducted at the Montcalm Research Farm in Entrican. They were planted in randomized complete block design, in four replications. The plots were 23 feet long and spacing between plants was 12 inches. Inter-row spacing was 34 inches. Both round and long variety groups were harvested at two dates. The yield was graded into four size classes, incidence of external and internal defects was recorded, and samples for specific gravity, chipping, bruising and cooking tests were taken. Chip quality was assessed on 20-tuber samples, taking two slices from each tuber. Chips were fried at 365°F. The color was measured with an M-35 Agron colorimeter and visually with the SFA 1-5 color chart. Prior to chipping, the tubers were stored at 45 and 50°F. Texture and after cooking darkening were assessed on five tuber samples. Results A. Round white varieties Nine varieties and 10 breeding lines were included in the trial. Atlantic, Eramosa, Onaway and Superior were used as checks. The average yield was higher than in 1989 and 1990. The results are summarized in Tables 1 and 2. NY87 at first date of harvest yielded significantly more U.S. No. 1 tubers than any other variety. However, 31 out of 39 over 3 1/4" tubers checked were hollow. At the second harvest date, NY87 yielded on the level of Atlantic and Onaway. NYE55-44 yielded on the level of Atlantic and Onaway at first harvest, being inferior to both at second harvest. It can be classified as an early variety with very attractive tubers. The performance of NYE55-35 confirmed its high potential as chipping variety. At the second harvest, its yield and specific gravity were comparable to those of Atlantic but it has a better internal quality than Atlantic. Two Wisconsin lines W856 and W870 were also in this class, while W887 yielded less than Atlantic, but had higher specific gravity (1.10). Calchip was a good yielder and had very high specific gravity, but has a very late maturity, rather small tubers and a high incidence of hollow heart this season. Eramosa. Superior, and Mainechip yielded much below the best varieties. Mainechip, however, had high specific gravity, good internal quality and has excellent chipping color. Variety Characteristics Eramosa - very early variety with smooth, round to oval tubers of good appearance. Yield potential and specific gravity very low. Has few internal defects. Susceptibility to silver scurf was noted. Has potential as a early fresh-market variety. Onaway - medium-early fresh market variety with excellent yield potential and a low specific gravity. Tubers are round to oblong, large, deep eyes, susceptible to growth cracks and early blight. Very good internal quality, storability poor. Atlantic - medium-late, chipping variety of high specific gravity and good yield potential. Susceptible to scab, soft rot, white knot, and to internal defects (hollow heart, vascular discoloration, internal brown spot). Superior - medium-early, fresh market variety. Tubers well- shaped, medium size, specific gravity medium. Resistant to scab but susceptible to Verticillium wilt. Calchip - very late, high yielding, high specific gravity, chipping variety. Tubers well shaped, but rather small and have a tendency to hollow. Gemchip - late, high yielding, fresh market and chipping variety. Tubers large, round to oblong, of good appearance. Specific gravity low. Some tendency towards hollow heart was noted. Mainechip - medium-late variety of excellent chipping quality. Comparable to Atlantic in specific gravity, lower yield potential, but better internal quality. Tubers are rather small. Norwis - medium-late, high yielding variety. Tubers are large, yet do not hollow. Excellent internal quality. Specific gravity too low for chipping industry. Spartan Pearl - medium-early, fresh market variety. Yield potential above average. Tubers well-shaped, uniform in size, and attractive. Specific gravity medium, good internal quality, but shows some tendency for after-cooking darkening. Susceptible to scab and growth crack. MS401-1 - yellow-flesh variety with outstanding chipping quality. Tubers well-shaped, but rather small. Specific gravity below that of Atlantic. Yield potential below average. Its major drawbacks are strong tendency to hollow heart and susceptibility to scab. MS402-8 - early, fresh market variety. Yield potential is low, slow emergence, but has long dormancy. Plan to delete from program. B9792-61 - early variety from USDA-Beltsville breeding program. Yield potential too low. NY87 - late variety, but sets tubers early. It was top yielder at both harvest dates. Tubers are large, but have a strong tendency to hollow heart and specific gravity is low for chip processing. NYE55-35 - late, medium to high yielding with high specific gravity and good chipping quality. Tubers well-shaped, medium large and uniform in size. Few internal defects and reported to have scab tolerance. Has a good potential in Michigan. NYE55-44 - medium-early, fresh market variety. Chipping quality is good but specific gravity rather low. Tubers are medium large, uniform, well-shaped and good general appearance. Good potential in Michigan. W856 - very late, fresh market and chipping variety with a high yield potential. Specific gravity slightly below that of Atlantic. Tubers large, eyes are deep, few internal defects, W870 - medium-late, chipping variety. Yield potential and specific gravity high. Tubers are medium-large and slightly flat. Few internal defects. Has a good potential in Michigan. Wisconsin plans to name this seedling. W877 - medium late, chipping variety. Average yield potential with high specific gravity. Tubers uniform in size, well-shaped and few internal defects. W887 - very late, high yielding and high specific gravity chipping variety. Tubers large, a little flattened, eyes rather deep. Average internal quality. Tendency to shatter wounds and short dormancy were noted. B. Long Varieties Seven varieties and three breeding lines were tested. The harvest was done 96 and 143 days after planting. The data are summarized in Tables 3 and 4. Castile has confirmed its outstanding yield potential. It is very late, but sets tubers early. It was the top yielder at both harvest dates. Of the breeding lines, W1005 was the best yielder at both harvest dates. All other varieties and breeding lines yielded below the level of Russet Burbank. Two breeding lines A78242-5 and MN12171 were at the very low end with respect to yield. W1005 and ND1538-1 (tested in North Central Region trial) are the only russet lines of some potential in Michigan. Incidence of hollow heart was generally high among long varieties. However, no hollow heart, despite its large tubers, was noted in Castile. Variety Characteristics Castile - very late variety of very high yield potential. Tubers are very large oblong, and well-shaped, yet do not hollow. White skin and good appearance. Specific gravity is medium, and internal defects are few. Susceptible to blackspot and some incidence of Altenaria solani. Early blight was noted on tubers during storage. W1005 - late, high yielding variety. Tubers are long and rather thin. Specific gravity high. Resistant to scab, susceptible to blackspot. Ranger Russet (A7411-2) - late, medium yielding, high specific gravity variety. Tubers are large and have good appearance. Few internal defects. Excellent potential for processing. Susceptible to blackspot. Frontier Russet medium-late variety with average yields. Specific gravity medium. Tuber appearance and cooking quality good. Shows some resistance to scab and some tendency to hollow heart. Russet Burbank - used as a standard in the trial. Late maturity, average yields. Specific gravity good for processing. Has a tendency to form off-shape and undersize tubers. Excellent appearance after boiling. Resistant to scab. Hilite - medium maturity with average yield and specific gravity. Has a tendency towards hollow heart. Russet Norkotah - early to mid-season variety. Yield potential and specific gravity rather low. Tubers oblong to long, well shaped. Resistant to scab. Some after cooking darkening was recorded in some years as well as susceptibility to Verticilium wilt. Eide Russet (MN10874) - medium-late, medium yield potential, low specific gravity. Tubers well shaped and have few internal defects. Resistant to scab. Susceptible to blackspot. A78242-5 - medium-late, average yield potential, medium specific gravity. Tubers well-shaped, blocky and attractive. Tendency for hollow heart and brown centers was recorded in 1991. Leaves may display mosaic at early stage which is not due to virus infection. MN12171 - medium early, low yield potential, with specific gravity comparable to Russet Burbank. Few internal defects. C. Adaptation Twenty-one advanced breeding lines from various states were compared to eleven varieties in the Michigan adaptation trial (Table 5). This experiment serves as a screen for the more intensive dates of harvest evaluations in the following years. Castile and Steuben confirmed their excellent yield potential. Five breeding lines - B0172- B0202-4. B0257-12. and S438 were comparable 15. AC80545-1 (Chipeta). to Castile and Steuben in yield. The most promising lines for fresh market are AC80545-1 and B0257-12. Both have well-shaped tubers, but their specific gravity is too low for chipping. B0172-15 had a strong tendency for hollow heart. B0202-4 had irregular tuber shape, was heavily infected with pitted scab, and showed tendency to form hollow heart. S438 was very late and had strong stolons. B0405-4. W887. and W842 yielded less than Castile and Steuben, but had very high specific gravity, an acceptable tuber shape, and good chipping quality. Should be further tested for chipping industry. W952. S440. and E57-13 had excellent chipping quality, but their yield potential was low. S440 had small tubers. E55-27. the top yielder in 1990, had an average yield in 1991. Since it is medium-late and a good chipper, it will be tested further. D. North Central Regional Trial The North Central Trial is conducted in 14 states and provinces, in a wide range of environments, to provide adaptability data for the release of new varieties. Twelve breeding lines of various tuber-type were compared in the 1991 trial. Red Pontiac, Russet Burbank, Norchip, Norland, and Norgold Russet were planted as check varieties. Two MSU lines, MS401-1 and MS402-8 were included in the trial in 1991. The results are presented in Table 6. Most of the new lines performed well and should be further tested. MN12567 is late, high yielding, fresh-market variety, however, the tubers were severely infected with Altenaria solani in storage. Two red-skin varieties, ND1871-3 and LA12-59 also produced very high yields- similar to Red Pontiac. LA12-59 was severely infected with Altenaria solani in tubers. Three Wisconsin lines W856. W870. and W877 yielded a little less, but had high (W856) to very high (W877) specific gravity. The chipping quality of W870 and W877 was excellent and W856 was acceptable. ND1538- 1 confirmed its good potential in Michigan as fresh market and processing variety of russet type. MS402-8 yielded too low and should be discarded while MS401-1 produced acceptable yield of excellent chipping quality. However, its tendency to hollow heart, smaller size, and susceptibility to scab may render it unacceptable for commercial growing. E. Processing and Quality Evaluation of Fresh-Peeled and Canned Potatoes From the MSU Variety Trials Tubers from approximately 6-8 cultivars and/or selections grown in Michigan and the MSU variety trials were used for processing as fresh- peeled and canned. Tubers from each processing lot were assessed for specific gravity and black spot. Samples were abrasion-peeled to approximately 10-12% peel loss and divided into lots for holding as fresh-peeled or diced for canning. Fresh peeled samples were held at 38°F after treating with 0.5% citric +0.5% ascorbic +0.1% NaCl2 or after dipping in water (control). These samples were evaluated at 0, 3, 5, 7 and 10 days for color (visual rating and Hunter CDM) and texture (shear press or Instron). Canned samples were diced and canned under commercial conditions. These samples will be removed from storage and evaluated at 0, 3, 6 and 9 months for drained weight, color (visual and Hunter CDM), and texture (shear press or Instron). Processing for fresh-peeled and canned product were done at harvest and will be done again after 6 months storage. Results of the 10 day storage regime for fresh-peeled potatoes are shown in Table 7. Changes in color and overall acceptability took place slowly during the first 3 days of refrigerated storage and there were no significant differences between the control and ascorbic acid treated samples. By day 5 the only control samples that had acceptable quality were Kanona, Superior and Viking but all of the ascorbic acid-treated samples except Eramosa were still acceptable. By day 7 only the ascorbic acid-treated sample of Onaway still had acceptable color and by the tenth day of storage none of the samples was acceptable. Table 8 shows the results of evaluation of the canned samples after 3 months. As expected, all samples gained weight in the can, with Superior and Russet Burbank showing the greatest gains. Viking, Eramosa, Superior and Onaway all had excellent color while Stueben and Atlantic exhibited very poor color. Visual assessment of texture was related to the wholeness and integrity of the diced potato pieces. Atlantic and Stueben scored lowest but all of the samples had very acceptable attributes in this category. The Kramer Shear data indicates that the samples were very similar in their shear characteristics. Shear values relate to the force necessary to move one or more shear cell blades through a given volume of sample inside a cell of defined size. Compression values were highest for Russet Burbank, Kanona, Atlantic and Stueben. It is likely that this is an indirect reflection of the starch content of these tubers and the changes which the starch granules have undergone during processing. F. Fusarium Dry Rot Evaluation As part of the postharvest evaluation, resistance to Fusarium sambucinum (fusarium dry rot) was assessed by inoculating whole tubers with a syringe and needle to a depth of 1 cm. The tubers were held at 20°C for three weeks and then scored for disease by measuring the depth and diameter of the decayed tissue. No absolute resistance was detected in the two groups of varieties that were screened (Table 9). Some varieties did, however, exhibit a lesser degree of rot than others. We will continue to conduct studies to determine if this lesser degree of rot is a valuable mechanism of reducing fusarium dry rot infection in storage. G. Upper Peninsula Variety Trial A potato variety trial was conducted by Dr. Rich Leep on the farm of Tim Barron in Rock. The plots were planted on June 7 and harvested on September 28. Overall yields were very good, however, specific gravity values were lower than normal. MS401-1, W1005 and Ranger Russet had the highest values. Two sources of Frontier Russet were compared. Frontier Russet (LC) was obtained from the breeder, Dr. Joe Pavek, in 1990 and Frontier Russet (JP) was obtained in 1991. There was no essential difference in the performance between the two seed sources. Frontier Russet appears to respond to light by developing a purple color on the stems and vine and also on the tuber surface. Table 1 ROUND WHITES DATES OF HARVEST HSU MONTCALM RESEARCH FARM AUGUST 11, 1991 (93 DAYS) YIELD(Cwt/ac) YIELD(Cwt/ac) PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION * DEFECTS DEFECTS * 3-YEAR AVE VARIETY US #1 TOTAL US#1 <2" 2-3 1/4" >3 1/4" PO SP.GR. HH VD US#1 NY87 W870 NYE55-44 ATLANTIC ONAWAY MS401-1 NORWIS GEMCHIP SPARTAN PEARL W856 W887 NYE55-35 SUPERIOR ERAMOSA MAINECHIP W877 CALCHIP MS402-8 B9792-61 AVERAGE LSD (.05) 475 409 406 394 389 387 378 374 366 365 355 334 334 321 313 275 251 225 188 344 65 510 463 428 432 450 457 403 420 444 395 375 391 372 351 362 347 327 255 243 391 67 93 88 95 91 86 85 94 89 82 93 95 85 90 91 86 79 77 88 77 6 11 5 9 7 15 5 10 16 5 5 14 8 6 12 21 23 9 18 77 81 90 78 69 82 64 81 78 82 80 77 88 75 86 78 77 80 77 16 7 6 13 18 3 31 8 5 11 15 8 1 16 0 1 0 8 0 31 4 1 16 0 7 1 6 0 4 3 4 0 1 0 1 0 2 1 --- --- --- 325 399 341** 359** 330** 362** --- --- --- 322** 319 302 --- --- 1.077 1.098 1.077 1.095 1.071 1.085 1.072 1.076 1.081 1.082 1.096 1.089 1.074 1.064 1.093 1.101 1.107 1.069 1.073 1 0/39 1 0/26 0 0/10 0 0/33 7 0/37 0 0/11 0/33 1 1 0/27 0/19 1 2 0/22 1 1/33 0/20 1 3 1/4 2 0/29 0/0 2 0 0/3 0 0/0 0/16 3 4 0/1 empty table cell empty table cell empty table cell empty table cell 1.083 empty table cell 0.003 empty table cell ---- --- 88 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell *NUMBER OF DEFECTS/NUMBER OF OVERSIZE TUBERS CUT **TWO-YEAR AVERAGE PLANTED MAY 10, 1991 Table 2. 1991 round whites-second date of harvest MSU MO NTCALM RESEARCH FARM SEPTEMBER 16, 1991 (129 DAYS) YIELD (CWT/AC) YIELD (CWT/AC) PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION * DEFECTS DEFECTS * * DEFECTS * DEFECTS 3-YEAR AVE. VARIETY US#1 TOTAL US#1 <2" 2-3 1/4" >3 1/4" PO SP.GR. HH BC IBS VD US#1 593 NY87 592 ATLANTIC 566 ONAWAY 543 W856 528 NYE55-35 527 CALCHIP 526 NORWIS 518 W870 517 GEMCHIP 485 W887 444 NYE55-44 SPARTAN PEARL 420 402 W877 379 MAINECHIP 377 MS401-1 358 SUPERIOR 320 ERAMOSA 292 MS402-8 220 B9792-61 AVERAGE LSD (.05) 453 82 617 615 603 572 571 595 544 558 567 515 473 489 464 432 454 407 362 316 263 96 96 94 95 92 89 97 93 91 95 94 86 86 88 83 88 88 92 84 4 3 4 3 8 11 3 6 8 3 6 14 13 11 16 11 8 5 15 66 72 70 68 77 84 51 80 75 55 86 82 81 85 77 84 75 77 80 1.075 1.092 1.072 1.085 1.091 1.112 1.068 1.095 1.071 1.100 1.075 1.079 1.099 1.089 1.082 1.071 1.060 1.067 1.071 empty table cell empty table cell 26 31 10 24 0 24 3 27 5 16 10 5 8 46 4 13 5 16 5 40 4 8 0 4 2 5 0 3 20 6 4 1 0 13 4 16 3 3 empty table cell empty table cell 0 1 2 2 0 0 0 1 1 3 0 1 0 1 1 1 3 3 1 empty table cell empty table cell --- 0 418 1 478 0 512** 0 460** 0 --- 0 498** 1 460** 1 499** 0 1 --- 435** 0 430 0 386** 0 347 0 362 0 391** 0 324 0 0 276 --- 1 empty table cell empty table cell 0 0/40 1 0/40 0 0/40 0 4/40 3 0/39 3/19 0 0 0/40 1 0/39 0 0/40 1 4/40 0 0/26 1 0/15 1 0/19 0 0/10 0 0/24 0 0/15 0 1/27 0 0/27 1 0/17 empty table cell empty table cell 1.082 empty table cell 0.004 empty table cell 495 91 empty table cell empty table cell 84 empty table cell empty table cell empty table cell empty table cell empty table cell *NUMBER OF DEFECTS/NUMBER OF OVERSIZE TUBERS CUT **TWO-YEAR AVERAGE PLANTED MAY 10, 1991 Table 3. LONG VARIETIES FIRST DATE OF HARVEST MSU MONTCALM RESEARCH FARM AUGUST 14, 1991 (96 DAYS) YIELD (CWT/AC) PERCENT SIZE PERCENT SIZE PERCENT SIZE PERCENT SIZE PERCENT SIZE 3-YEAR AVE. TOTAL DISTRIBUTION US #1 DISTRIBUTION<4OZ DISTRIBUTION 4-10OZ DISTRIBUTION>10OZ DISTRIBUTIONPO SP. GR. HH* US#1 VARIETYYIELD (CWT/AC) US #1 CASTILE W1005 R. NORKOTAH FRONTIER (LC) FRONTIER (PAVEK) A78242-5 R. BURBANK EIDE RUSSET RANGER RUSSET HILITE RUSSET MN12171 AVERAGE LSD (.05) 409 346 337 319 307 303 295 293 269 267 167 301 65 496 484 427 394 406 360 449 391 377 347 279 17 27 18 18 21 16 28 24 25 21 34 61 66 61 58 56 66 58 63 66 57 51 22 6 18 23 20 18 7 12 5 20 8 82 71 79 81 75 84 65 75 71 77 59 74 1 2 3 1 4 0 7 0 3 2 7 0/40 4/21 4/40 11/38 20/36 5/34 11/25 5/32 3/13 14/40 5/16 1.0833 1.0908 1.0737 1.0768 1.0771 1.0783 1.0838 1.0793 1.0888 1.0685 1.0873 1.0807 empty table cellempty table cell empty table cell empty table cell empty table cellempty table cell 0.004 409 362** 287 276 276 290 241 278 283 257** --- 401 72 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell * NUMBER OF DEFECTS/NUMBER OF OVERSIZE TUBERS CUT **TWO-YEAR AVERAGE PLANTED MAY 10,1991 Table 4. SECOND DATE OF HARVEST LONG VARIETIES MSU MONTCALM RESEARCH FARM SEPTEMBER 30, 1991 (143 DAYS) 3-YEAR AVE. PERCENT SIZE DISTRIBUTION4-10OZ PERCENT SIZE DISTRIBUTION<4OZ 12 13 16 14 14 16 17 17 14 14 23 YIELD (CWT/AC) VARIETY US #1 CASTILE 612 W1005 528 RUS. BURBANK 461 HILITE RUSSET 446 FRONTIER (LC) 414 RUS. NORKOTAH 407 RANGER RUS 384 FRONTIER (PAV) 333 EIDE RUSSET 331 A78242-5 329 MN12171 273 AVERAGE 411 176 LSD (.05) *NUMBER OF DEFECTS/NUMBER OF OVERSIZE TUBERS CUT YIELD (CWT/AC) TOTAL 686 631 585 515 496 513 466 419 394 397 369 497 187 empty table cell PERCENT SIZE DISTRIBUTIONUS #1 88 83 79 85 83 80 82 80 84 82 72 82 66 61 56 59 57 55 64 59 62 57 57 PERCENT SIZE DISTRIBUTION>10OZ 23 23 23 26 26 25 18 21 22 25 15 empty table cell empty table cell PERCENT SIZE DEFECTS * VD DISTRIBUTIONPO 0 0 4 0 4 1 0 1 3 3 4 2 1 1 3 1 2 2 4 0 5 2 empty table cell empty table cell empty table cell empty table cell SP. GR. DEFECTS*GE 1.0816 0/40 1.0873 0/40 1.0823 0/40 0/40 1.0738 0/40 1.0756 4/39 1.0811 1.0890 0/40 1.0740 0/38 1.0725 0/39 1.0804 0/40 1.0811 0/23 1.0799 empty table cell empty table cell empty table cell 1.010 empty table cell DEFECTS *BC 0 0 1 0 0 0 0 0 0 0 0 empty table cell empty table cell US#1 543 445 330 322 339 313 372 339 312 336 --- empty table cell empty table cell DEFECTS * IBD 0 1 1 0 0 0 0 4 1 14 4 DEFECTS*HH 0 9 21 19 18 6 8 15 8 17 5 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell PLANTED MAY 10, 1991 Table 5. ADAPTATION TRIAL MSU MONTCALM RESEARCH FARM SEPTEMBER 25, 1991 (138 DAYS) PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION PERCENT SIZE DISTRIBUTION YIELD(CWT/AC) YIELD(CWT/AC) DEFECTS * DEFECTS * * DEFECTS VARIETY US #1 TOTAL US #1 2-3 1/4" >3 1/4" PO <2" 1 5 4 1 6 4 5 4 8 2 6 8 5 2 7 9 7 8 11 4 5 12 17 8 15 5 7 26 7 12 22 19 48 45 53 74 64 87 82 77 60 75 80 47 60 76 77 85 82 67 76 60 83 79 80 81 69 78 70 63 86 71 74 93 45 94 45 90 45 97 18 93 31 96 6 92 14 96 14 92 96 36 93 17 91 11 44 91 95 35 91 15 12 89 91 7 89 7 19 86 93 17 91 32 88 5 82 3 89 9 84 3 26 95 93 15 4 74 71 8 86 0 78 7 90 empty table cell empty table cell BC VD *HH IBS 6 2 6 2 1 1 2 0 0 1 2 0 5 3 2 2 1 3 3 2 3 0 1 3 1 0 0 0 21 2 0 SP.GR. DEFECTS 1.084 0/40 1 1.078 0/40 0 1.075 0/40 0 0/40 1.080 0 0/28 1.078 0 0/40 1.078 0 1.087 0 1/28 1.059 1 2/33 1.093 1/36 5 1.093 0/40 1 1.074 0 0/36 4/36 1.093 1 1.074 0 0/40 0 0/40 1.066 1.079 1 0/37 0 1.089 0/39 1.100 1 1/27 1.086 0 0/15 1.082 0/40 1 1.096 0/39 0 1.082 0 0/39 0 1.082 0/40 0/11 1.082 0 1.078 1 1/27 1.094 0 0/11 1.071 1 0/40 1.070 0 0/29 1.091 0 0/11 0 0/18 1.084 1.054 0 0/0 1.068 0/20 0 empty table cell 1.081 empty table cell empty table cell empty table cell 0.004 0 25 4 0 8 2 4 0 11 0 0 9 0 1 0 0 0 6 0 3 0 0 5 0 2 7 0 0 2 2 0 9 0 2 6 0 0 2 0 2 4 0 9 0 0 0 2 0 4 0 0 2 3 0 2 0 0 2 0 0 4 0 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell B0172-15 CASTILE AC80545-1 STEUBEN B0202-4 B0257-12 S438 CHIEFTAIN B0405-4 W887 SAGINAW GOLD W842 NISKA VIKING W936 MS716-15 TRENT MS401-7 NYE55-27 W760 MS401-2 B0257-3 SNOWDEN W952 S440 MS402-7 KANONA W845 BO175-21 DK RED NORLAND NYE57-13 AVERAGE LSD (.05) 643 642 620 602 584 556 549 546 535 491 488 469 468 435 429 423 400 388 386 378 377 375 363 363 363 323 310 291 288 288 284 441 94 694 684 690 619 630 582 594 567 581 509 527 514 517 461 471 475 437 431 446 406 412 423 439 410 428 341 333 390 394 335 363 487 90 *NUMBER OF DEFECTS/NUMBER OF OVERSIZE TUBERS CUT PLANTED MAY 10, 1991 Table 6. VARIETY MN 12567 ND1871-3R RED PONTIAC LA12-59 W856 ND1538-1 NORCHIP W870 R. BURBANK W877 MN 12966 MS4O1-1 MN 13035 NORGOLD RUS NORLAND MS402-8 AVERAGE LSD (.05) NORTH CENTRAL REGIONAL TRIAL MSU MONTCALM RESEARCH FARM SEPTEMBER 25, 1991 (135 DAYS) YIELD (CWT/AC) YIELD(CWT/AC) US #1 TOTAL PERCENT SIZE DISTRIBUTION US #1 PERCENT SIZE DISTRIBUTION>2" PERCENT SIZE DISTRIBUTION 2-3 1/4" PERCENT SIZE DISTRIBUTION>3 1/4" PERCENT SIZE DISTRIBUTIONPO DEFECTS * HH DEFECTS * BC DEFECTS * IBS SP.GR. 576 570 568 547 516 505 459 452 427 396 391 378 360 346 336 209 440 79 672 625 628 585 534 576 508 481 595 431 436 430 435 441 361 231 498 78 86 91 91 93 96 88 90 94 72 92 90 88 82 78 93 90 88 14 7 3 4 3 9 5 5 16 8 7 12 12 19 6 8 66 74 49 67 63 54 77 79 53 84 77 78 77 60 82 81 20 17 42 26 33 34 14 15 19 7 12 10 6 17 11 9 empty table cell empty table cell 0 2 6 2 0 3 5 1 12 0 3 1 5 3 1 2 empty table cell empty table cell 1.079 1.065 1.066 1.078 1.085 1.071 1.076 1.094 1.086 1.099 1.071 1.082 1.064 1.068 1.055 1.067 empty table cell 1.075 empty table cell 0.004 empty table cell empty table cell 0/40 1/40 1/40 0/40 2/40 0/40 2/35 0/36 2/40 2/24 1/28 0/27 0/16 1/40 0/25 0/15 0 3 8 0 3 1 3 8 17 2 0 19 0 17 0 2 0 1 0 0 2 0 1 0 0 0 1 0 0 0 1 0 empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell empty table cell * NUMBER OF DEFECTS/NUMBER OF OVERSIZE TUBERS CUT PLANTED MAY 13, 1991 Table 7. - Quality Evaluation of Fresh Peeled Potatoes, 1991. Cultivar Russet Burbank Day 1 w/Asc 82/ Onaway Kanona Superior Viking Eramosa Atlantic Stueben 8 8 9 8 7 8 7 1 Day CK1/ 8 8 8 9 8 7 8 7 Day 3 Day 5 Day 7 Day 7 Day 10 Day 10 w/Asc CK Day 3 w/Asc Day 6 CK w/Asc 8 8 8 8 8 6 8 6 6 5 2 4 6 7 8 7 6 6 3 5 6 6 5 4 6 5 4 5 6 6 4 3 0 5 4 3 2 2 4 1 CK - 2 3 4 3 2 - - w/Asc 3 2 2 2 1 1 3 0 CK - - - - - - - - 1 w/Asc - with ascorbic acid; CK = control without ascorbic acid 2 1 to 10; 1 = poorest, 10 = best; the scores shown are subjective ratings of a combination of color and overall acceptability. Table 8. - Quality Evaluation of Canned Potatoes After 3 Months Storage, 1991. Force in lbs/100g in lbs/100g3/ Force 3/ Cultivar Drained wt (g)1/ Visual Color2/ Visual Texture2/ Shear Compression Russet Burbank Onaway Kanona Superior Viking Eramosa Atlantic Stueben 438.6 395.9 419.2 462.9 405.7 370.5 433.0 428.0 6 9 8 9 10 10 5 4 1/ Fill wt = 341 g (12 ozs) 2 /1 to 10; 1 = poorest, 10 = best 3 / Kramer Shear Press 7 9 8 8 7 8 6 5 36 30 33 33 30 30 36 36 87 63 87 76 66 63 87 81 Table 9. Fusarium Dry Rot Resistance Evaluation. Trial 1 Lesion diameter, mm Trial 2Lesion diameter, mm Atlantic Calchip B9792-61 Eramosa E55-35 E55-44 Gemchip Mainechip NY87 Norwis Spatan Pearl Superior 401-1 402-8 W856 W870 W877 W887 22.4 31.6 52 30.4 26.6 20.4 14.8 152 25.6 32.0 15.8 122 23.6 13.4 21.0 26.0 27.4 16.6 A78242-5 AC80545-1 B0202-4 B0175-21 B0405-4 B0172-15 B0257-3 B0257-12 B9792-6 Chieftain Eide E57-13 Frontier Hilite Kanona LAI 259 MN12567 MN13035 Mnl266 Niska ND1538-1 Norgold Norland NY87 Onaway Ranger S440 S438 Steuben Trent W760 W842 W845 W887 W936 W952 Viking 401-7 402-7 716-15 11.8 10.6 12.2 4.0 9.0 11.0 6.8 4.8 3.0 10.4 18.0 72 2.4 5.0 21.2 26.6 4.8 22.4 16.6 21.8 3.0 15.0 14.0 19.0 15.2 20.4 7.0 242 24.2 11.4 3.4 9.6 9.0 15.8 7.0 5.4 9.8 10.2 15.0 13.8 Table 10. UPPER PENINSULA POTATO VARIETY TRIAL R. Leep, J. Lempke, B. Buehrly and R. Chase Farm Cooperator - Tim Barron, Cornell, MI Yield cwt/A U.S. No. 1 Total Yield cwt/A Percent Size Distribution U.S. No. 1 Percent Size Distribution <4 oz Percent Size Distribution >10 oz 3 1/4" Percent Size Distribution Pick Outs Specific Gravity Scab* 406 372 367 344 307 299 297 295 290 286 274 271 256 255 249 249 211 188 159 282 448 413 378 424 385 347 337 344 315 345 304 293 302 292 284 321 233 210 200 325 90 90 97 81 79 87 88 81 90 83 90 93 85 86 87 75 90 90 80 86 10 10 3 14 13 11 10 19 9 11 10 6 14 14 13 23 10 10 19 11 10 19 21 21 19 34 22 24 19 4 22 11 7 16 12 7 6 1 0 0 0 5 8 2 2 0 1 6 0 1 1 0 0 2 0 0 1 1.075 1.079 1.071 1.072 1.074 1.069 1.077 1.076 1.071 1.072 1.080 1.072 1.068 1.064 1.068 1.063 1.069 1.066 1.060 1.071 -- -- -- -- -- + + -- + -- -- + + + + + + + + empty table cell empty table cell empty table cell empty table cell Variety Saginaw Gold W1005 Steuben HiLite Frontier Russet (JP) Russet Norkotah Frontier Russet (LC) Ranger Russet A78242-5 Russet Burbank MS401-1 Eide ND1538-1 Norwis Gemchip Sangre Kanona MS402-8 Red Norland AVERAGE *Scab: + - present, -- - not present Planted: June 7, 1991 Harvested: September 28, 1991 Seed Spacing: 12" FundingFederal Grant/NPC 1991 POTATO SCAB RESEARCH R. Hammerschmidt, D. Douches, K. Jastrzebski, C. Wallace Departments of Botany and Plant Pathology and Crop and Soil Sciences East Lansing, MI 48824 Each year a replicated field trial is conducted to assess resistance to common and pitted scab. In 1991, 86 varieties and advanced breeding lines were planted in a scab innoculated field at the MSU Soils Farm. These data are summarized in Table 1. The varieties are ranked on a 1-5 scale based upon a combined score for scab coverage and lesion severity. Examining one year's data does not indicate which varieties are resistant but should begin to identify ones that can be classified as susceptible to scab. Our goal is to evaluate important advanced selections and varieties in the study at least three years to obtain a valid estimate of the level of resistance in each line. The varieties that have been tested at least three years out of the last four are summarized in Table 2. In our assessment, certain points can be made at this time. The check varieties (Superior, Norgold Russet, Onaway and Atlantic) have ratings that are well correlated with their past characterizations. In general, few new varieties and advanced selections have high levels of resistance. The round white varieties (tablestock and chip-processing types) have little if any usable resistance. Russet varieties tend to have higher levels of resistance. The greenhouse pot test was used to compare the level of scab resistance between a series of varieties and their respective russet sports. There was no significant difference for scab resistance between the varieties and its sport suggesting that the russet skin is not a significant factor in determining scab resistance in a clone. To have a higher probability of breeding scab resistant round white varieties, scab assessment must be initiated early in a breeding program. A greenhouse test was developed to assess scab resistance at the seedling stage (described in previous progress reports). We have conducted a study to determine the correlation between this seedling test and greenhouse pot and field tests and found a high correlation between the seedling and greenhouse pot tests. The 1991 field test had limited levels of infection, therefore it did not correlate well with the greenhouse results. Additional greenhouse and field tests will be conducted to study this relationship. We have incorporated this seedling screen into the breeding program so that we can identify the most susceptible seedlings. These plants are then eliminated from the breeding program before more intensive evaluation of agronomic traits is initiated. This should increase the probability that scab resistant round white varieties can be bred for Michigan. A genetics study was conducted to evaluate the potential to breed scab resistant varieties from the cultivated germplasm. In greenhouse seedling and pot tests, the most resistant parent (Lemhi Russet) transferred the highest level of resistance to its progeny, and the most susceptible parent (ND860-2) produced the lowest family means for resistance. Surprisingly, Atlantic was a better parent to transmit scab resistance than the more resistant varieties Superior and Onaway. We are also in the process of identifying scab resistance in the related Solanum species. We hope these sources will offer greater levels of resistance than those we currently find in the cultivated potato. At this time we are intensively examining collections of two species, Solanum phureja and S. chacoense, which show higher levels of scab resistance. We are focusing on these species because some selections have been noted to carry high specific gravity and chip-processing potential. A study was initiated using a diploid population, in conjunction with a saturated genetic map (based upon RFLPs, RAPDs and isozyme genetic markers) to identify chromosome segments that may contain genes controlling scab resistance. A replicated greenhouse pot test was used to assess scab resistance in the population. Isozyme analysis has been used to characterize the population, while RFLP and RAPD analysis currently is being conducted to characterize the population. Statistical analyses to determine linkage between genetic markers and scab resistance will proceed this phase of the study. Table 1. 1991 Scab Evaluation MSU Soils Farm East Lansing, MI 1* 2 3 4 5 BO175-21 BO175-21 Castile Eramosa Yukon Gold A78242-5 Atlantic BO172-15 BO257-3 Calchip Kanona MS401-2 NDD277-2 Ni ska Norwis Ranger Russet Red Lasoda Red Pontiac Eide Russet Frontier Russet Hilite Russet MN12171 MN12567 ND1538-1 Rus. Norgold R. Norland NYE57-13 Russet Burbank R. Norkotah S438 Sebago Superior W1005 White Rose B9792-61 Early Rose Green Mtn. Mainechip MN12966 MS401-7 MS402-8 MS716-15 NYE55-27 NYE55-44 Onaway Ontario S440 Viking W842 W845 W877 W936 *1 - no incidence of scab 5 — high incidence of scab AC80545-1 B0202-6 B0405-4 Chieftain Dk. Rd. Norland Gemchip I. Cobbler Katahdin Kennebec LA12-59 MN13035 MS401-1 MS402-7 Norchip NY87 NYE55-35 Saginaw Gold Shepody Snowden Spartan Pearl Steuben W760 W856 W870 W887 W952 Table 2 Scab Field Test Summary Variety Ranking empty table cell 1988 - 1989 1990 1991 Ave. - Lemhi R. R. Norkotah Frontier R. Norgold R. Superior Eide R. MS402-8 Castile Rosegold W231 Ranger R. Onaway Mainechip MS716-15 A78242-5 Spartan Pearl Saginaw Gold Snowden Norchip Red Lasoda MS402-7 Steuben Atlantic B0257-3 B0172-15 Eramosa Shepody MS401-2 MS401-1 2 - 3 - 3 2 - 2 2 2 1 3 3 - 3 3 4 5 - 4 4 3 - - 3 3 3 5 1 1 1 - 2 3 4 1 2 2 4 3 - - 3 3 4 - - 1 3 3 1 1 4 4 - 4 5 1 1 2 1 3 2 2 2 3 3 2 4 3 4 3 3 3 3 2 4 4 3 5 5 2 3 5 4 4 *Resistant: <2 Moderately resistant: 2.0-2.5 Susceptible: 2.6-3.0 Very susceptible: >3.0 1 1 1 1 1 1 4 - - 2 2 2 1 2 2 2 2 2 4 1 3 4 4 4 4 3 4 2 1.0* 1.2 1.3 1.6 2.0 2.2 2.2 2.3 2.3 2.3 2.5 2.5 2.6 2.6 2.6 2.7 3.0 3.0 3.0 3.0 3.0 3.2 3.2 3.3 3.3 3.5 3.6 3.7 4.0 Funding Federal Grant MANAGEMENT PROFILE OF STEUBEN R.W. Chase, R.B. Kitchen and K. Jastrzebski Department of Crop and Soil Sciences Introduction Management profile studies have been conducted on selected varieties and advanced seedlings since 1986 in order to evaluate the effect of plant spacing and nitrogen levels. The Steuben study was initiated in 1991 as interest had been expressed for this variety as a possible fresh market variety. Steuben is a very late maturing variety released by Cornell in 1989. It has a high yield potential but does set and size tubers early. Procedure Three levels of nitrogen (100, 150 and 200 lbs/A) and three in-row spacings (6, 9 and 12 inches) were studied. The seed was hand cut to obtain uniform seed size of l 1/2 to 2 ounces and was hand planted on May 13 in a randomized split plot design. Each plot was 23 feet long with four replications. At plowdown, 300 lbs/A of potassium sulfate (0-0-50) was applied broadcast. At planting, a 20-10-10 fertilizer was banded at 200 lbs/A to all of the plots. Two border rows were established between the main plots of nitrogen levels and the variable nitrogen rates were applied as a sidedress treatment on May 22, 1991. Soybeans were grown as a plowdown crop in 1990 and rye was planted in the fall. The area was treated with 50 gpa of sodium methyl dithocarbamate (Busan 1020) in November of 1990. Thimet was used as the systemic insecticide and foliar insect and disease controls were applied as needed. The study was irrigated using the MSU Irrigation Scheduling Program. Results The yields, percent size distribution and specific gravity are shown in Table 1. The results are in descending order based on yields of U.S. No. 1 potatoes. These data show that the closer spacings produced the higher yields of marketable potatoes. There was considerable variability in this study as the stands were less than desired. The overall stand for the 6 inch spacing was 78%, 91% for the 9 inch and 83% for the 12 inch spacing. Fusarium dry rot was present in the seed and did affect the final stand. Table 2 summarizes the results by spacings and nitrogen levels. These data show that the closer spacings produced the best marketable yields. The percentage of tubers over 3 1/4 inch increased with the wider spacing and there was no effect on specific gravity. Hollow heart in the larger tubers also increased with the wider spacings. In terms of nitrogen level, the highest yield of marketable potatoes was obtained at 200 lbs N/A. The lowest yield occurred at the 150 lb level and reflects the variability of this study. Specific gravity was higher at the higher nitrogen levels and hollow heart did increase at the 150 and 200 lb/A levels. The number of tubers were counted in two replications and showed an average of six tubers per hill. At hairvest, considerable tuber rot was noted in all plots. It appears that Steuben may be susceptible to bruising which leads to subsequent breakdown. Steuben has a very late maturity which can limit good skin set at harvest. Table 1. Steuben Management Profile - Montcalm Research Farm. Treatmen Treatmen t *N/AC t Spacing Yield (cwt/AC) U.S. No. 1* Yield (cwt/AC) Total Percent Distribution U.S. No. 1 Percent Distribution Percent Distribution Percent Distribution <2" 2-3 1/4" >3 1/4" Percent Distribution Pick Outs Specific Gravity 6 6 7 6 7 5 4 6 4 3 1 2 9 1 2 2 4 4 57 61 65 54 66 47 57 51 52 34 33 25 31 27 46 36 39 40 91 93 91 85 92 93 94 90 92 91 6" 9" 6" 9" 6" 12" 12" 9" 12" 587 509 519 541 495 473 457 431 402 490 533 a 475 ab 471 ab 463 abc 457 bc 439 bed 429 bed 388 cd 373 d empty table cell 448 200 100 150 200 100 200 100 150 150 AVERAGE LSD 76 Planted May 13, 1991 Harvested September 30, 1991 (140 days) *Least significant difference test. Values with the same letters are not significantly different. empty table cell empty table cell empty table cell 1.080 1.076 1.080 1.079 1.076 1.079 1.076 1.077 1.079 1.078 empty table cell Table 2. Steuben Management Profile Summary of Nitrogen and Spacing Levels. Yield (cwt/A) Yield (cwt/A) Percent Percent Percent Distribution Percent Distribution No. 1 Total Distribution No. 1 Distribution<2" 2-3 1/4" >3 1/4" Percent Distribution Pick Outs S.G. Internal Defects* HH Internal Defects* VAS DIS Internal Defects* Brown Center Internal Defects* Tubers Cut Nitrogen Space (Ibs/A) (in.) empty table cell 6 empty table cell9 empty table cell12 1.0 2.0 2.0 0.3 3.0 1.0 *Number of internal defects noted in the sample of oversized tubers cut. empty table cell empty table cell empty table cell 1.078 1.077 1.078 1.076 1.078 1.079 487 442 414 454 410 478 534 494 444 487 451 533 28 34 41 32 35 37 63 55 52 61 56 53 91 89 93 93 91 90 100 150 200 3 4 6 3 5 5 7 6 4 6 6 6 2 5 3 1 3 5 1.0 1.0 1.0 2.0 0.7 0.3 40 40 40 40 40 40 Funding MPIC Effects of Nitrogen Fertilizer Management on Nitrate Leaching J.T. Ritchie and E. Martin Department of Crop and Soil Sciences The goal of this study is to minimize the loss of nitrate-N out of the root zone but still produce a good economic yield. Increasing public awareness of nitrate contamination of groundwater has caused agriculturalists to focus their attention on nitrogen recommendations and management strategies. This study, which began in 1988, evaluated the impact of nitrogen fertilizer management on the leaching of nitrates out of the root zone. Using two permanently installed drainage lysimeters, the drainage water and nitrate-N leaching were measured. The lysimeters were separated by treatment, one receiving a conventional nitrogen treatment (CON) and the other receiving a more conservation/research nitrogen treatment (RES). Each year, the RES plot has received less nitrogen fertilizer than the CON plot. METHODOLOGY The lysimeters used in this study are steel boxes that are 48 in. wide, 68 in. long, and 6 ft. deep, and are open at the top. The open tops of the lysimeters are located about 1.5 ft. below ground surface and drainage samples are taken from the bottom of the lysimeters, at a depth of approximately 7.5 ft. At the bottom of each lysimeter, there is a small opening where drainage water from inside the lysimeter is discharged. From the opening, the amount of drainage water is measured and samples are taken. These samples are then tested for nitrate-N concentration and the amount of nitrogen lost can be calculated. In 1991, a new automated sampling device was installed in the lysimeters. The auto-sampler measured the water draining from the lysimeters and then automatically pumped a sample from the drainage water for nitrate-N analysis. The sampler is set to pump a sample whenever 0.25 inches of water has drained through the soil profile. The plots were hand-planted on May 28 with the Saginaw Gold variety. At the time of planting, the RES plot received 500 lbs/A of 5-10-15 (25 lbs N/A), placed at the bottom of the furrow cut, just below the seed. The CON plot received 500 lbs/A of 15- 10-15 (75 lbs N/A) that was also placed in the bottom of the furrow. Row spacing was 34 inches and seed spacing was nine inches. Additional nitrogen was added to the plots throughout the season. On July 27, the CON received 125 lbs N/A as urea and the RES plot received 50 lbs N/A as urea. The urea was worked into the ground. On August 6, an additional 50 lbs N/A was applied to the RES plot. The total amount of nitrogen added to the two plots was 200 lbs N/A for the CON plot and 125 lbs N/A for the RES plot. Irrigation for the two plots basically followed the same schedule as the rest of the Montcalm Research Farm. The plant leaves in the RES plot were mostly senesced by August 22. The plants in the CON plot began to lose green leaf area on August 27, and were completely senesced by September 9. The tubers in both plots showed no signs of disease or rot and were generally in excellent condition. The plants in the lysimeter areas were hand harvested. The plants in the plot areas were mechanically dug up, and then hand harvested. Four samples, in addition to the lysimeter samples, were taken from each plot. The samples were 20 feet of a single row. The potatoes were separated according to size and condition, and weighed. Sub-samples were taken from each harvest sample for specific gravity measurements. RESULTS The results for this study will be split into two sections: first, the 1991 results will be reviewed and then the cumulative results for the past four years will be discussed. Results: 1991 As in 1990, the tuber yields in the RES treatment were less than those measured in the CON treatment. Overall, the RES treatment yielded 78 cwt/A less than the CON treatment. As Table 1 shows, the RES treatment yielded more small tubers, less than 2 inches, whereas the CON treatment yielded more pick-outs. The distribution of size was 18%, 72%, 0%, and 10% for the CON treatment and 46%, 50%, 0%, and 4% for the RES treatment, for the four sizes given in Table 1. The lysimeter drainage data for 1991 are shown in Figs. 1-3. Figure 1 shows the cumulative drainage that occurred during the past year. Throughout most of the year, the two lysimeters drainage was approximately the same. However, toward the end of the season, the lysimeter drainage on the RES plot increased. This may be due to the early leaf senescence that occurred in that plot and would cause less water to be taken up, allowing more drainage to occur. The nitrate leaching data are shown in Figs. 2 and 3. Figure 2 shows the nitrate-N concentrations for the drainage water from the two lysimeters. The CON lysimeter consistently had a higher nitrate-N concentration. Nitrate-N concentrations dropped in both lysimeters as the season began with some spikes of increase occurring during the growing season. Table 1. Tuber yield and quality in term of size distribution, pick outs, and specific gravity, for Montcalm Research Farm Lysimeter plots, 1991. Yield (cwt/A) Yield (cwt/A) Size Distribution Size Distribution TRMT * Sample Total < 2" Size Distribution 2"-2.75" > 3.25" CON CON CON CON CON CON RES RES RES RES RES RES CON1 CON2 CON3 CON4 CON LYS AVE RES1 RES2 RES3 RES4 RES LYS AVE 254 201 248 209 254 233 164 164 151 111 183 155 35 28 42 42 61 42 76 80 58 48 98 72 205 142 176 131 179 167 85 81 78 57 83 77 0 0 5 0 0 1 0 0 0 0 0 0 * Samples consisted of 20 feet of a single row (samples 1-4) and of the lysimeter area (LYS). Specific Gravity 1.079 1.090 Pick Size Distribution Outs 15 31 25 36 13 24 1.077 1.077 1.083 1.081 4 3 15 6 10 7 1.072 1.067 1.069 1.067 1.080 1.071 The nitrate-N loss for the season is shown in Fig. 3. This shows that the CON treatment continues to lose more nitrogen as the year progresses. The measurements show that by the end of 1991, 15 lbs N/A more leached from the CON lysimeters than from the RES lysimeter. This low difference is probably due to the early senescence of the plant leaves in the RES treatment. Of the 125 lbs N/A applied to the RES treatment, about 51 lbs N/A was removed by the tubers, but some would be contained in the plant tops and roots. Figure 1. Nitrate-N concentrations of the drainage water from the RES and CON lysimeters. Montcalm Research Farm, 1991. Figure 2. Cumulative drainage for the RES and CON lysimeters. Montcalm Research Farm, 1991. Figure 3. Cumulative Nitrate-N leached for the RES and CON lysimeters. Montcalm Research Farm, 1991. Results: 1988-1991 Studying data obtained over a long period gives a better perspective on long term trends and/or impacts. Table 2 shows the relative yield of the RES treatment compared to the CON treatment. In 1988 and 1989, the RES treatment yields were comparable to the CON yields, with a reduction of 1.2 and 5.4 percent in each year. However, in the past two years a decrease in yield of about 1/3 has occurred. The nitrogen fertilizer strategy for the RES treatment for the last two years has been to look for signs of nitrogen deficiency and apply only the amount of nitrogen required for adequate growth. This strategy, called Plant Response Fertilization (PRF) should minimize nitrate leaching while maintaining good yields. However, if the nitrogen stress is too severe before it is detected, a reduction of yield may occur, as found in the yields of the RES treatment for 1990 and 1991. This indicates that the PRF strategy is inadequate for potato production although it does contribute to reduced leaching. Table 2. Percent reduction in crop yield due to reduced nitrogen fertilizer application in the RES treatment for the years 1988 through 1991. Montcalm Research Farm. YEAR CROP TYPE Percent Reduction of Yield in RES Treatment 1988 1989 1990 1991 Potatoes Corn Potatoes Potatoes 1.2 5.4 33.8 33.5 The overall effect of the nitrogen management strategies on nitrate leaching has been a steady decrease in nitrate-N leached from the RES lysimeter while the CON lysimeter continues at a somewhat constant rate. Table 3 shows the nitrogen fertilizer applied, the nitrogen removed by the harvest, and the nitrogen loss in leaching. Adding these values over the years of study, Table 3 shows that at the end of 1989, the RES lysimeter received 160 lbs N/A less than the CON lysimeter, but produced the same yields and lost approximately the same amount of nitrogen through leaching. However, by the end of the following two years, the RES lysimeter had received about 325 lbs N/A less, taken up about 70 lbs N/A less, and leached about 100 lbs N/A less than the CON Table 3. Cumulative nitrogen inputs and outputs for both the RES and CON treatments for the years 1988 through 1991. Montcalm Research Farm. Year 1988 1989 1990 1991 Crop Type Potatoes Corn Potatoes Potatoes CUMULATIVE NITROGEN (LBS/A) CUMULATIVE NITROGEN (LBS/A) CUMULATIVE NITROGEN (LBS/A)Fertilizer Fertilizer Removed by * Harvest CUMULATIVE NITROGEN (LBS/A) Removed by * Harvest RES CON RES CON 110 240 350 475 200 400 593 793 80 180 248 299 81 187 289 368 CUMULATIVE NITROGEN (LBS/A) Leached CUMULATIVE NITROGEN (LBS/A) Leached RES 58# 258 368 442 CON 73# 288 448 532 * N uptake calculated assuming 0.33 lbs N/cwt of potatoes and 1.5% nitrogen concentration in the corn grain. # Leaching measurements began in July, 1988. lysimeter. Performing a nitrogen balance and assuming no change in the organic matter content for the past four years, the plants in the RES treatment have used about 248 lbs/A of mineralized nitrogen while the plants in the CON treatment have used only 95 lbs/A of mineralized N. The leaching data are shown in Figs. 4, 5, and 6. Figure 4 shows the drainage data for the last four years. Drainage from the two lysimeters was about the same. Figure 5 is the nitrate-N leached from the lysimeters for the past four years. About the same amount of nitrogen is leached from the two lysimeters during the first two years and then the RES treatment began leaching less. By the end of 1991, the RES treatment had leached 90 lbs N/A less then the CON treatment. However, Fig. 6 can give some insight into trends. By plotting cumulative nitrate-N leached versus cumulative drainage (Fig. 6), the nitrogen leaching trends can be seen. The lysimeters lost nitrate-N at about the same rate for the first 10 inches of drainage. This coincides with the drainage that occurred up to the end of 1989 (see Fig. 4). At that point, the RES lysimeter began to lose nitrate-N at a slower rate. This is indicated by the lower slope of the curve. During the next two years, the rate of nitrate-N loss has continued to go down in the RES lysimeter while the CON lysimeter’s rate has been fairly constant. DISCUSSION AND CONCLUSIONS 1991 Season The reduced yields in the RES treatment for the last two years indicate a weakness in the conservative approach of PRF. The RES treatment was intended to provide the most conservative approach to nitrogen fertilization in order to determine if there was a correlation between the nitrate-N leaching and the amount of nitrogen not removed by the harvested potatoes. This year, an attempt was made to measure nitrogen stress by measuring plant height, number of leaves, and number of stems. Unfortunately, these measurements did not give sufficient early detection of a nitrogen deficiency in enough time to correct the deficiency. The relatively low yields and early senescence the plant leaves in the RES plot indicate that the final 50 lbs N/A applied may not have had any beneficial effect on the crop yield. 1988-1991 The data for the last four years gives some insight into how nitrogen fertilization has impacted the leaching of nitrates. Early data, from 1988 and 1989, seem to indicate that the nitrate losses were due to previous years management and that the treatment effects were not yet causing the differences in leaching. In 1990, we began to see a Figure 4. Cumulative drainage from the RES and CON lysimeters from 7/88 through 10/91. Montcalm Research Farm. Figure 5. Cumulative nitrate-N leached from the RES and the CON lysimeters from 7/88 through 10/91. Montcalm Research Farm. Figure 6. Cumulative nitrate-N leached versus cumulative drainage for the RES and CON lysimeters from 7/88 through 10/91. Montcalm Research Farm. change in the nitrate-N loss from both lysimeters. Figure 6 shows a slight decrease in the nitrate-N leaching rate for the CON lysimeter and a large decrease for the RES lysimeter. We realize the yield reductions of the last two years due to PRF are unacceptable. There still is a need to develop a strategy that will minimize nitrate leaching while still maintaining a good yield. The results of this study indicate that the only way to reduce leaching losses in potato production is through doing the best job of matching the nitrogen supply with the plant’s nitrogen demand. The leaching losses caused by nitrogen mineralization from organic matter can’t be controlled and will be lost. Funding Federal Grant NITROGEN MANAGEMENT TO IMPROVE POTATO YIELD, QUALITY, AND GROUNDWATER QUALITY M. L. Vitosh, R. H. Leep and G. H. Silva Department of Crop and Soil Sciences INTRODUCTION Choosing the optimum nitrogen fertilizer rate for potatoes is a complex decision for the potato growers. The growers are advised to consider all sources of available nitrogen(N) from soil reserves and supplement any remaining requirement with fertilizer N. These soil reserves include fertilizer N residue from previous crop, N mineralized from organic matter and decomposing crop residues. Such reserves are site-specific and predictions of the N availability are not entirely reliable at present. Nitrogen undergoes rapid transformations and movement in the soil and potentially could be lost from the root zone. The potential for N leaching associated with growing potatoes increases greatly when N application rates exceed the crop requirements. Nitrate contamination of groundwater has become an important environmental issue in Michigan. The mounting concern that fertilizer practices have an adverse effect on the quality of our environment has prompted a reexamination of the current N management practices. The development of new management strategies that improve the efficiency of both applied fertilizer N and available soil N can lead to a reduction in the overall fertilizer N use as well as the risk of groundwater contamination. One way to achieve this goal would be to reduce the at-planting N fertilizer rate and apply supplemental N as needed during the growing season. This approach would function optimally if combined with plant tissue and soil testing techniques that allows for rapid assessment of the crop N status and the N supplying capacity of the soil. The concept is to allow soil reserves to supply as much N as possible and supplement fertilizer N when the crop needs it. This would ensure that minimal N is left in the soil profile following harvest. The results from previous studies have indicated that the petiole sap nitrate concentration is a sensitive guide to the N status of potatoes. To utilize this technique as an effective on-farm N management strategy, a quick and reliable procedure for sap nitrate analysis is needed. If the sap nitrate N level is found to be below a critical range, then the grower can resort to in- season corrective fertilization, thereby increasing the N use efficiency and minimizing the risk of groundwater contamination. OBJECTIVES 1. 2. 3. To develop and calibrate a quick and reliable test procedure for measuring petiole sap nitrate N; To establish critical nutrient ranges for petiole sap N in relationship to growth stage and tuber yield; To field test and validate the use of sap nitrate test as an index of crop N status and soil N availability, and asses its use as a guide for corrective in-season N fertilization. MATERIALS AND METHODS Field trials were conducted at the Montcalm Research Farm, MSU soils farm, E. Lansing, and in the Upper Peninsula. At Montcalm and MSU, the treatments included five N fertilizer rates and six potato varieties. The N rates were 0, 60, 120, 180, and 240 lbs N/A (Table 1). The treatments 2-5 received 60 lbs of N at planting and the balance was sidedressed at tuber initiation as ammonium nitrate. Preplant applications of P and K were made according to soil test recommendations. The six varieties included were Onaway, Superior, R. Norkotah, Atlantic, Snowden and R. Burbank. In the Upper Peninsula, only two varieties (R. Norkotah and R. Burbank) and four N rates (0, 60, 120, 180 lbs N/A) were tested. The plots were 50 feet long and spaced 34" apart. The treatments were tested in a split plot design, with N as the main plot and replicated four times. A. Soil Sampling for Nitrate and Ammonium analysis A random preplant soil sample (0-12" deep) from the experiment site was taken just prior to planting. The zero N plots were sampled every week for 9 consecutive weeks to study N mineralization and availability in the soil. During the season, all N plots were sampled at emergence, tuber initiation, 2 weeks after tuber initiation, and after harvest. In the after harvest sampling, all N and variety plots were sampled to a depth of 2 feet in 1 foot increments to assess the residual N in the soil. B. Petiole sampling for nitrate N analysis. All plots were sampled once a week starting at tuber initiation (before the sidedress application) and continued for 5 consecutive weeks. The sap nitrate concentration was determined by the procedure developed at MSU. Samples were taken in the morning hours and consisted of 15-20 petioles taken from the fourth or fifth fully expanded leaf. In a zip lock bag, the sap was squeezed out and mixed with an extraction solution consisting of aluminum sulfate and boric acid. The nitrate N concentration of the extract was determined with a nitrate ion specific electrode. The two early varieties (Onaway and Superior) were harvested on August 26. Atlantic and R. Norkotah were harvested on September 9. The late varieties Snowden and R. Burbank were harvested on September 23. Tubers were graded according to size and the yield and percent of US # 1 tubers determined. The specific gravity was measured by weighing samples in air and water. RESULTS AND DISCUSSION Petiole sap nitrate test The technique for determining petiole sap nitrate N was effective as a rapid on-farm procedure that would permit a grower to monitor the N status of the crop during the season. The development of this method was made possible by the recent introduction of non-clogging electrodes. Historically a major drawback has been that the electrodes readily clogged in the presence of viscous and colloidal extracts. The electrode used in this procedure was designed with a free diffusion reference junction that provide fast, stable and reproducible exchange potentials free from clogging. This test does not involve any hazardous chemicals and could be assembled into a small portable kit. A highly significant linear relationship (R2 = 0.92) was found between the nitrate N content measured by the quick sap test and the conventional oven-dried tissue procedure. This shows that the sap nitrate test with a quick turnaround can be used instead of the more time consuming conventional methods to assess the N status of the plants during the season. Petiole sap N level in response to N rate and sampling date Petiole sap nitrate concentration was highly sensitive to soil N and increased in proportion to the N fertilizer application rate, even up to 240 lbs N/A (Figs. 1 and 2). The changes in the sap nitrate level with sampling date are illustrated in Figs. 3 and 4. In general, the petiole nitrate N level is higher at the beginning of the season and decreases as the season progresses. This pattern, however, is interrupted in response to supplemental N applications. The combined effects of N fertilizer rate and sampling date on the petiole sap nitrate concentration at Montcalm and MSU are illustrated in Figs. 5 and 6, respectively. At the 0 and 60 lbs N/A , the sap nitrate concentration decreased rapidly with sampling date. At higher N rates, the sap nitrate N concentration remained steady and showed only a small decrease with time. The average weekly declined in the sap nitrate level for the 5 N rates in shown in Table 2. The petiole sap concentration decreased by greater than 100 ppm per week in the 0 and 60 lbs N treatments. Soil Test Data Soil N transformations in the zero N plots at Montcalm and MSU are shown in Figs. 7 and 8, respectively. This data illustrates the N supplying potential of the soil. With the onset of spring, microbial activity convert organic matter into ammonium and then to nitrate. The nitrate level peaked about 28 days after planting. This corresponds with the time of potato emergence. In the following weeks, the available soil N begins to deplete as the crop's demand for N increased. It was estimated that the check plots could provide as much as 100 lbs nitrate N/A on both locations. This study reiterate that the initial N in the soil and the potential for mineralization are crucial in determining the optimum fertilizer N rate for potatoes. The soil test N levels measured during the season closely corresponded with the N rates applied to plots (Figs. 9 and 10). The test results from the final soil sampling is still being analyzed. This data will indicate the quantity of the residual N left in the soil after potato harvest. Tuber Yield, Quality and Critical Nutrient Range The tuber yield, percent US #1, and specific gravity of potatoes are presented in Tables 3-8. In both locations, significant yield responses were observed only up to 120 lbs applied N /A. The response to 60 and 120 lbs N varied depending on the variety and location. In many varieties, the percent of US #1 tubers was slightly lower in the zero N treatment compared to the N treated plots. The specific gravity tended to decrease with increased N, however, significant differences were only observed in Snowden and Russet Burbank. In order to establish the critical nutrient ranges for the sap nitrate, linear regression techniques were applied to the sap N concentration corresponding to the 5 N rates and dates of sampling. By superimposing regression curves with the yield response observed at each N rate, the sap nitrate levels were partitioned into inadequate, adequate, and excessive segments. Between the adequate and inadequate segments, is a range of concentration designated as borderline or Critical Nutrient Range (CNR). The CNR is defined as the range of concentration above which the crop is amply supplied and below which the crop is deficient to the extent that significant yield reductions would occur. In our study, the critical nitrate concentrations for most varieties were found to be comparable and a nutrient range was established to encompass all varieties and locations. The critical nutrient levels and their interpretations are presented in Table 5. Once the CNR is established it can be used as a guide to assess the N status of a given potato crop if the growing stage is known. It is evident that as growth advances, the CNR progressively decrease, meaning that it is not essential to maintain a high soil N status throughout the growing season. Most varieties responded only up to 120 Ibs/A of added N fertilizer. The data presented in Table 2 indicated that at N rates of 0 and 60 lbs/A, the sap N concentration decreased by greater than 100 ppm per week. The magnitude of this decline provides an added clue to the N status of the crop. If a grower measures the potato sap concentration at a particular time, and finds it to be within the CNR, it might be worthwhile to wait another week until corrective fertilization is applied. If in the following week, the sap N concentration is still within the CNR, but has decreased by more than 100 ppm, then it is advisable to apply supplemental N. If the concentration remains the same or has increased in the following week, the indication is that there is sufficient N in the soil. The nitrogen rates tested in the Upper Peninsula are presented in Table 10. The yield data is summarized in Table 11. The previous crop at this location was alfalfa. This would partially explain the lack of clear yield response to added N at this location. Visual observations indicated that the zero N plots senesced earlier than the N treated plots. At all N rates, the US #1 yields of Russet Burbank were higher than R. Norkotah. Tuber size increased with higher N rates. In R. Norkotah, there was a significant increase in the percent tubers >10 oz. in all N treated plots compared to 0 N. Nitrogen treatments did not significantly affect the specific gravity of R. Norkotah, however, increasing N rates appeared to lower the specific gravity of R. Burbank. Petiole sap nitrate concentration as of August 6 ranged from 500 ppm in the 0 N to 1390 ppm in the 180 lbs N treatment (Fig. 11). As in the other 2 locations, the sap nitrate levels decreased rapidly with time in the 0 N treatments. At 180 lbs N, the sap nitrate level remained steady with time. The Nitrogen mineralization curve (Fig.12) indicated that as high as 138 lbs N/A became available in the 0 N plots from soil organic matter by the middle of July. Nitrogen level rapidly declined thereafter presumably due to increased uptake by potatoes. Soil test N levels during the season closely corresponded with the N rates applied to plots (Fig.13). Soil samples taken on July 31 indicated that all plots receiving fertilizer N tested greater than 100 lbs nitrate-N/A. FUTURE RESEARCH Future research should focus on expanded field testing and validating of the sap nitrate test. The test should assess the N availability in the soil, improve N fertilizer efficiency and produce high quality potato yields. One aspect that needs to be further investigated is the timing of the test, particularly in relation to changes in soil moisture level. The sap nitrate test could serve as a decision support mechanism for growers who are concerned with possible late season N deficiencies. The expanded use of the sap nitrate test in conjunction with soil tests, would enable the grower to manipulate N fertilizer rates so as to leave minimal residual N in the field. Such an integrated approach would help identify instances where the soil N mineralization rates are high, where potatoes are not likely to respond to addition of N fertilizer, and where the potential for groundwater contamination is high. Table 1. Nitrogen rates (lbs/A) and time of application in 1991 field experiments. Treatment # At-planting Tuber initiation Total N 1 2 3 4 5 0 60 60 60 60 0 0 60 120 180 0 60 120 180 240 Table 2. The average weekly decrease in the petiole sap nitrate concentration(ppm) in response to N fertilizer rate at Montcalm and MSU. N rate (lbs/A) Montcalm 0 60 120 180 240 212 186 98 69 58 MSU 164 126 42 35 37 Table 3. Yield of US # 1 potatoes (cwt/a) in relation to fertilizer nitrogen fertilizer rate. Montcalm 1991. N rate lbs/a 0 60 120 180 240 Onaway Superior R.Norkotah Atlantic Snowden R.Burbank 306.8 b 227.6 b 328.0 c 364.7 b 286.1 b 316.6 b 354.8 ab 310.8 a 394.5 a 393.0 a 299.1 a 310.2 a 374.2 ab 291.9 a 358.2 bc 416.1 ab 429.7 a 424.4 a 412.1 a 428.4 a 440.4 a 434.6 a 340.9 b 352.9 ab 421.9 a 403.5 a 434.9 a 421.7 a 463.5 a 395.8 a Table 4. Percent of US # 1 potatoes in relation to fertilizer nitrogen rate. Montcalm 1991. N rate lbs/a 0 60 120 180 240 Onaway Superior R.Norkotah Atlantic Snowden R.Burbank 88 90 91 90 88 91 95 96 96 96 92 93 94 94 93 96 97 97 97 97 91 92 95 94 94 78 83 80 78 73 Table 5. Specific gravity of potatoes in relation to fertilizer nitrogen rate. Montcalm 1991. N rate lbs/a 0 60 120 180 240 Onaway Superior R.Norkotah Atlantic Snowden R.Burbank 1.067 1.067 1.068 1.068 1.066 1.068 1.070 1.070 1.070 1.068 1.070 1.070 1.071 1.070 1.068 1.087 1.088 1.091 1.091 1.088 1.077 b 1.083 a 1.083 a 1.086 a 1.084 a 1.080 1.081 1.081 1.080 1.080 Table 6. Yield of US # 1 potatoes (cwt/a) in relation to fertilizer nitrogen fertilizer rate. MSU 1991. N rate lbs/a 0 60 120 180 240 Onaway Superior R.Norkotah Atlantic Snowden R.Burbank 256.3 b 185.7 b 248.9 b 329.6 b 253.5 b 332.9 b 287.7 ab 245.2 a 314.8 ab 345.6 ab 318.8 a 411.5 ab 314.8 a 317.6 a 316.6 a 234.4 ab 262.1 a 229.9 ab 370.5 a 385.0 a 355.1 a 392.1 a 375.4 a 378.9 a 334.5 a 427.5 ab 315.7 a 450.3 a 324.6 a 367.8 ab Table 7. Percent of US # 1 potatoes in relation to fertilizer nitrogen rate. MSU 1991. N rate lbs/a 0 60 120 180 240 Onaway Superior R.Norkotah Atlantic Snowden R.Burbank 87 89 91 90 89 85 96 94 94 95 90 92 90 93 92 96 96 96 96 94 93 93 93 91 91 68 65 62 60 60 Table 8. Specific gravity of potatoes in relation to fertilizer nitrogen rate. MSU 1991. N rate lbs/a 0 60 120 180 240 Onaway Superior R.Norkotah Atlantic Snowden R.Burbank 1.065 1.069 1.068 1.068 1.067 1.064 1.068 1.067 1.066 1.066 1.066 1.068 1.070 1.068 1.067 1.082 1.081 1.084 1.081 1.081 1.072 b 1.079 a 1.079 a 1.078 ab 1.075 ab 1.076 b 1.082 a 1.081 a 1.080 a 1.075 b Table 9. Proposed guidelines for interpreting sap nitrate concentration (ppm) of potato petioles for six weeks starting from a week after tuber initiation (TI) Interpretation GDD* GDD* for Montcalm for MSU Inadequate Critical Range Adequate Excessive June 27 TI + 7 885 970 < 1200 1200-1399 1400-1599 >1600 July 3 TI + 14 1038 1144 < 1100 1100-1299 1300-1499 > 1500 July 9 TI + 21 1175 1271 < 1000 1000-1199 1200-1399 > 1400 * Growing degree days (base 50 F) since planting July 17 TI + 28 1430 1575 < 900 900-1099 1100-1299 > 1300 July 24 TI + 35 1530 1674 < 800 800-999 1000-1199 > 1200 Aug 1 TI + 42 1690 1846 < 700 700-899 900-1099 >1100 Table 10. Nitrogen Applied (lbs/A) to 1991 trial in the Upper Peninsula Treatment Number Planting Tuber Initiation Total N Applied 1 & 2 3 & 4 5 & 6 7 & 8 0 60 60 60 0 0 60 120 0 60 120 180 Table 11. The effect of rate and time of nitrogen fertilizer application on yield, tuber size and specific gravity of potatoes in the Upper Peninsula Treat -ment No. N rate lb/A 1 2 3 4 5 6 7 8 0 0 60 60 120 120 180 180 Variety R Norkotah R Burbank R Norkotah R Burbank R Norkotah R Burbank R Norkotah R Burbank U.S. No 1cwt/A Total Yield cwt/A Tuber Size Distribution Tuber Size Distribution #1Percentage Percentage <4 oz Tuber Size Distribution >10 oz Percentage Tuber Size Distribution PickoutPercentage Specific GravityPercentage 250 295 264 300 249 293 283 308 304 bc 361 abc 304 bc 393 a 293 c 384 ab 321 bc 417 a 82 ab 82 ab 87 a 76 bc 85 a 76 bc 88 a 74 c 18 a 16 a 13 b 14 b 15 ab 10 bc 12 b 12 b 11 c 14 bc 16 ab 15 bc 16 ab 15 bc 21 a 17 ab 1 b 2 b 0 b 9 a 0 b 14 a 0 b 14 a 1.073 1.086 1.070 1.085 1.070 1.081 1.073 1.082 Means within a column followed by the same letter are not significantly different (p<.05) according to the LSD test. Fig.1. Petiole nitrate concentration in relation to N rate - Montcalm 1991 Fig.2.Petiole nitrate concentration in relation to N rate MSU 1991 Fig 3. Sap nitrate level in relation to date of sampling - Montcalm 1991 Fig 4. Sap nitrate level in relation to date of sampling - MSU 1991 Fig 5. Petiole sap Nitrate in relation to N rate and sampling date at Montcalm Fig 6. Petiole Sap Nitrate in relation to N rate and sampling date at MSU Fig.7. Nitrogen transformations in zero N plots at Montcalm 1991 Fig 8.Nitrogen transformations in zero N plots - MSU 1991 Fig 9. Soil test N in relation to fertilizer N rate - Montcalm 1991 Fig 10. Soil test N in relation to fertilizer N rate - MSU 1991 Fig.11 Petiole Sap Nitrate in relation N rate and sampling date - U.P. 1991 Fig 12. Nitrogen mineralization in the Upper Peninsula 1991 Fig 13. Soil test N in relation to fertilizer N rate-Upper Peninsula Funding _____ MPIC_____ UNDERSTANDING THE RESPONSE OF POTATOES TO PHOSPHORUS Darryl D. Warncke and William B. Evans Department of Crop and Soil Sciences Michigan State University Although the phosphorus requirement of a potato crop is similar to that of other field and vegetable crops, potatoes require higher levels of phosphorus fertilization to produce good yields. Field studies with Russett Burbank potaotes have shown improved yields with band application of phosphorus at planting time even though phosphorus soil test levels have been very high, greater than 400 lb P/A. This is a source of concern for efficient use of resources, monetary and phosphorus, and for the loading of phosphorus into surface waters. On fields where surface runoff occurs phosphorus is carried with the soil. With these issues in mind a better understanding of the response of potatoes to soil and fertilizer phosphorus is needed. A number of studies were conducted in 1991 to improve our understanding of the response of potatoes to phosphorus. Preliminary studies have indicated that the soluble phosphorus concentration in many soils used for growing potatoes is very low and may be limiting phosphorus uptake and potato plant growth. Potato plants were grown in solution culture to study the ability of potato roots to take up phosphorus from solution at varying phosphorus concentrations. In two separate studies plants of Atlantic, Sebago and Onaway were grown in aerated nutrient solution containing limited phosphorus. The roots of these plants were able to reduce the concentration of phosphorus to between 0.05 and 0.08 mg/1 which is similar to that found in the soil solution of some soils. In a separate study plants of Atlantic and Sebago potatoes were grown for 8 hours in aerated nutrient solutions containing six different phosphorus concentrations. The relative rate of phosphorus uptake decreased greatly as the solution phosphorus concentration was decreased (Table 1). At a solution concentration of 0.1 mg P/l (many soils have solution concentrations less than this) the phosphorus uptake rates were less than 20 and 15 percent of the maximum, respectively, for Atlantic and Sebago. McBride sandy loam soil was collected from two separate fields and blended to give a range of available soil phosphorus from 200 to 700 lb P/A. In a previous field study each soil blend had received the equivalent of 0, 50, 100, 150 or 200 lb P2O5 /A. Prior to using the soil in this greenhouse study each soil treatment was thoroughly mixed and fumigated. Two sets of each soil treatment were put into 3 gallon containers. Corn was grown for 5 weeks in one set and Russett Norkotah potatoes were grown for 8 weeks in the other set. The objective was to compare the response of com and potato to the indigenous soil phosphorus and to applied phosphorus fertilizer. This study primarily provided a comparison of the vegetative growth stages, although at harvest the potato plants had set some tubers. Data presented in Tables 2 and 3 indicate that the soil phosphorus level and the rate of phosphorus fertilization had little effect on the vegetative top growth of the oom or potatoes. However, the level of soil phosphorus did affect the underground development of the potato plant (Table 4). Although the number of tubers set after 8 weeks of growth were similar across all soil phosphorus levels, the number of rhizomes and the number of set tubers plus initiated rhizome tips (potential tubers) did increase with soil phosphorus level. This indicates that phosphorus may improve the potential for better yields by stimulating increased tuber numbers. To further evaluate the effect of soil phosphorus level and phosphorus fertilizer application on potato growth and yield, Russett Norkotah potatoes were grown in McBride sandy loam soil contained in a 12 inch length of a 10 inch diameter solid plastic tile. McBride sandy loam soil was collected from two separate fields and blended to give soil with extractable phosphorus levels ranging from 200 to 900 lb P/A. The soil was fumigated with Metham to eliminate nematodes and verticillium (early die complex). The tile were placed vertically in a trench prior to being filled halfway with the respectively blended soil. A ring of phosphorus fertilizer was placed on the soil to provide the equivalent of 0, 50 ,100, 150 or 200 lb P2O5/A. After adding two more inches of soil a tuber was placed in each container and each container was filled with the respective soil blend. The potatoes were grown to maturity with watering and supplemental nitrogen and potassium as needed. The yield data for this study are given in Tables 5 and 6. There was no interaction between soil phosphorus level and phosphorus fertilizer rate. Total tuber weight and tuber numbers tended to increase with increasing level of phosphorus in the soil. However, the biggest increase occurred in going from a soil phosphorus level of 200 lb P/A to 375 lb P/A. Specific gravity of the tubers decreased as the soil phosphorus levels increased. This may have been do to more small tubers being present with the higher phosphorus levels. Total tuber weight and tuber numbers tended to be increased by increased rates of phosphorus fertilizer (Table 6). The biggest increase occurred with the first 100 lb P2O5/A. Addition of more phosphorus was of little benefit. Specific gravity was not affected by the rate of phosphorus fertilization. Hence, it appears that near maximum tuber yields can be obtained with a soil phosphorus level of 375 lb P/A and a fertilizer rate of 100 lb P2O5/A. Much of the potato-phosphorus response data has been developed with the cultivar Russett Burbank. Since Russett Burbank is a long season variety the response to phoshporus may differ from that of other varieties. Six varieties, Atlantic, Onaway, Snowden, Superior, Russett Burbank and Russett Norkotah were grown at three locations with four phosphorus fertilizer rates; 0, 75, 150 and 225 lb P2O5/A. This group of varieties includes both fresh market and chip types, and early and late season varieties. Each of the varieties was planted at the Montcalm Research Farm on a McBride sandy loam on May 3 and on an Essexvelle loamy sand in Bay County on April 26. Each treatment was replicated four times. Planting at the Monroe County site was delayed by heavy rains and wet soil until May 21. This site was plagued by heavy rain and most of the plots were lost to flooding. Hence, no meaningful data was collected from the Monroe County site. At the Montcalm Research Farm five hills were harvested early, August 6, from the no and high phosphorus fertilizer rows of each variety to determine whether any differences existed in the development of tubers to that point in time. The harvest data is presented in Table 7. For Superior and Atlantic there were more tubers per hill with the potatoes receiving phosphorus. For the other varieties the tuber numbers were similar regardless of phosphorus fertilization. Total yield of tubers was markedly higher with phosphorus for Atlantic, but for Snowden the tuber weight was higher in the no phosphorus plots. With the exception of Russett Norkotah and Onaway the percent of tubers of less than 2 inch diameter or 4 ounce in weight was higher for the potatoes receiving phosphorus. This indicates there was more potential for increased yield by the potatoes receiving phosphorus. Specific gravity was higher in the potatoes fertilized with phosphorus for the Superior and Atlantic varieties. With the other varieties specific gravities were similar regardless of phosphorus fertilization. End-of-season yield data are given in Table 8 for the four round white varieties grown on the McBride sandy loam with a phosphorus test level of over 500 lb P/A . With Atlantic total tuber yield and yield of 2 to 3.25 inch tubers were significantly increased by the application of phosphorus fertilizer. With the other three varieties there was a trend toward higher tuber yield with phosphorus fertilizer application, but the differences were not significant. In general there was a trend toward inproved specific gravity with phosphorus application. Phosphorus fertilization with 75 lb P2O5/A improved total tuber and 4 to 10 ounce tuber yields of Russett Norkotah (Table 9). Increasing the phosphate rate beyond 75 lb P2O5/A provided no additional increase in tuber yield. Tuber yields of Russett Burbank were not affected by phosphorus fertilization. The specific gravity of Russett Norkotah tubers was inproved by phosphorus application. Growing conditions at the Bay County site were less than ideal during much of the growing season. The soil test phosphorus level in this Essexville loamy sand averaged 515 lb P2O5/A. The soil was quite wet during the early part of the growing season. Later in the season it was hot and dry, although water was applied by irrigation. Tuber yields were not significantly affected by phosphorus application in all six varieties (Tables 10, 11 and 12). Tuber yields of Superior were inproved by application of up to 150 lb P2O5/A although the increase was not significant. With the low tuber yields phosphorus apparently was not a limiting factor. With higher yields and a greater demand for phosphorus a response to applied phoshorus would be more likely. Phosphorus application had no effect on specific gravity of tubers of all six varieties from this location. Core samples of the tubers were analyzed for the nutrient content. The phosphorus content of the tubers, averaged across all varieties, increased as the phosphorus fertilizer increased. On the McBride sandy loam the average phosphorus contents of the harvested number 1 tubers were 0.206, 0.208, 0.218 and 0.228 percent on a dry weight basis for phosphorus fertilizer rates of 0, 75, 150 and 225 lb P2O5/A. The same respective phosphorus contents for the tubers harvested from the Essexville loamy sand were 0.242, 0.260, 0.279 and 0.273 percent. The order of phosphorus concentration in tubers of the six varieties was the same at the two sites. The average phosphorus content of the varieties across the two sites was: Atlantic - 0.210 %; Snowden - 0.214 %; Onaway - 0.244 %; Superior - 0.242 %; Russett Burbank - 0.250 %; Russett Norkotah - 0.279 %. Hence, depending on the variety and the specific gravity the phosphorus removal in the harvested tubers will be near 4 lb P/cwt (9.1 lb P2O5/cwt). In summary, even though the roots of potatoes have the ability to take up phosphorus at very low concentrations in solution, the rate of phosphorus uptake is greatly reduced compared with the uptake rate at higher solution phosphorus concentrations. Thus in soils having lew levels of phosphorus in the soil solution extensive root growth would be necessary for adequate phosphorus uptake to occur. Greenhouse studies indicate that the response of potatoes to high levels of phosphorus is not in vegetative growth , but is related to the effects on initiation of rhizomes and tubers. Rhizome numbers and number of initiated tuber tips increased with soil phosphorus level. In a field study the number of tubers set and developed increased with increasing soil phosphorus levels and with phosphorus fertilizer application up to 100 lb P2O5/A. The yields of Atlantic and Russett Norkotah potatoes were significantly increased by the application of 75 lb P2O5/A when grown on a McBride sandy loam having an extractable phosphorus level of over 500 lb P/A. With the other four varieties (Onaway, Snowden, Superior and Russett Burbank) there was only a limited response to the application of phosphorus. When grown in an Essexville loamy sand with a phosphorus test level of 515 lb P/A none of the six varieties responded to the application of phosphorus fertilizer. The effect of phosphorus fertilization on specific gravity was mixed. In most cases phosphorus application had no effect on specific gravity, but in a few cases the highest rate of phosphorus application did increase the specific gravity. Table 1. Ability of potato roots to reduce the phosphorus concentration in a nutrient solution. Relative Uptake Rate Initial Solution P Concentration 8 hour change in P concentration in P concentration 8 hour change Atlantic mg P/l 0.07 0.11 0.25 0.55 1.26 2.79 % 2 8 20 53 95 100 mg/l .016 .061 .147 .382 .691 .724 Sebago mg/l .014 .049 .055 .385 .748 .992 Relative Uptake Rate % 1.4 5 6 39 75 100 Corn Top Fresh Weight Table 2. Corn and potato growth with increasing soil phosphorus. Soil P level2 lb P/A 200 325 450 575 700 *Bray-Kurtz P1 extractable phosphorus in a Mc Bride sandy loam. g 265 274 287 290 270 g 197 186 202 189 194 Potato Top Fresh Weight Table 3. Corn and potato growth with increasing phosphorus fertilization. Phosphorus Potato Corn Top Fresh Weight Top Fresh Weight Rate lb P2O5/A 0 50 100 150 200 g 273 290 277 268 271 g 198 190 195 189 196 Table 4. Influence of soil phosphorus level on potato rhizome and tuber development. Soil P Level lb P/A 200 325 450 575 700 Rhizomes #/plant 5.6 4.6 5.7 6.4 7.1 Tubers Set #/plant 3.1 3.4 3.7 3.1 2.4 Set Tubers + Initiated Tips #/plant 10.2 7.7 11.8 12.3 14.2 Table 5. Influence of extractable soil phosphorus level on the yield of potatoes (cv.Russett Norkotah) grown in McBride sandy loam soil.z Soil Py level lb P2O5/A 200 375 550 725 900 Total Yield cwt/A Yield > 4ozcwt/A 211 242 220 257 248 98 108 83 107 108 Number Number Total Tuber/Plant > 4oz Tuber/Plant 1.7 1.9 1.5 1.8 1.9 7.0 7.9 8.1 6.8 8.6 Specific Gravity 1.071 1.069 1.068 1.067 1.066 zSoil was contained in a 12 inch length of a 10 inch diameter plastic tile. Yield data is across five different fertilizer rates. ySoil P level as determined by Bray-Kurtz Pl extraction. Table 6. Influence of phosphorus fertilization on the yield of potatoes (cv Russett Norkotah) grown in McBride sandy loam soil.z soil py level lb P2O5/A Yield Yield Total cwt/A > 4oz cwt/A 53 109 104 115 122 170 229 259 250 271 0 50 100 150 200 1.069 1.067 1.069 1.068 1.068 zSoil was contained in a 12 inch length of a 10 inch diameter plastic tile. Yield data is across five different fertilizer rates. yYield data is across five different soil P levels. 6.3 7.1 8.0 8.1 9.0 Specific Gravity Number er Numb Total Tuber/Plant >4oz Tuber/Plant 1.1 1.9 1.8 1.9 2.1 Table 7. Influence of phosphorus fertilzation on potato growth and yield data in a McBride sandy loam. Harvested August 6, 1991. Variety P2O5 Rate Onaway Onaway Superior Superior Atlantic Atlantic Tubers/ Hill 10.3 9.7 7.1 8.3 Total cwt/A 350 362 310 318 310 370 350 320 empty table cell 10.7 10.0 7.6 9.5 0 225 0 225 0 225 0 225 >2" by wt. < 2" count Specific Gravity % 89 89 77 79 93 89 % 35 37 38 44 25 32 1.064 1.063 1.064 1.069 1.086 1.091 Snowden Snowden empty table cellempty table cell Rus. Burbank Rus. Burbank Rus. Norkotah Rus. Norkotah 0 225 0 225 9.7 9.7 6.1 5.7 82 74 empty table cell> 4oz 67 55 82 83 300 275 317 300 1.078 1.077 38 47 < 4oz empty table cell 61 69 50 37 1.070 1.071 1.066 1.067 Table 8. Influence of band phosphorus applicaton on the yield of four round white potato varieties grown in a Mc Bride sandy loam. Yield Totalcwt/A d >3 Yiel Yiel d 2-3 Yield<2"cwt/A Specific Gravity Phosphorus Rate lb P205/A Superior Superior 190 181 180 206 ns empty table cell Onaway Onaway 219 198 206 233 ns Atlantic empty table cell Atlantic 0 75 150 225 0 75 150 225 0 75 150 225 1/4" cwt/A 1/4" cwt/A SuperiorSuperior 17 a 8 b 6 b 6 b 154 156 157 176 empty table cell ns OnawayOnaway 75 ab 60 b 76 ab 84 a 128 119 116 132 empty table cell ns AtlanticAtlantic Superior Superior 17 b 15 b 17 b 22 a 1.063 b 1.064 b 1.064 b 1.067 a empty table cellempty table cell Onaway Onaway 11 ab 6 c 8 be 12 a 1.063 1.064 1.063 1.063 ns Atlantic empty table cell Atlantic 110 116 112 101 ns 34 37 39 46 ns 230 b 325 ab 351 a 348 a 23 26 29 29 ns Snowden empty table cell SnowdenSnowden 377 397 378 388 ns 41 38 38 42 ns 1.082 b 1.085 a 1.085 a 1.084 ab empty table cell Snowden 1.079 b 1.079 b 1.080 ab 1.83 a empty table cell 373 b 472 ab 497 a 489 a empty table cellempty table cell Snowden Snowden 0 75 150 225 empty table cell 459 478 459 483 ns Table 9. Influence of band phosphorus applicaton on the yield of two long white russett potato varieties grown on a McBride sandy loam. Phosphorus Rate Yield Totalcwt/A Yield >10 oz 4-10 ozcwt/AYield Yield <4 ozcwt/A Specific Gravity - - - cwt/A lb P205/A Russett NorkotahRussett Norkotah Russett Norkotah Russett Norkotah 202 b 55 223 ab 51 55 243 a 228 ab 53 empty table cellns 436 b 474 ab 488 a 489 a 161 184 168 191 ns Russett NorkotahRussett Norkotah 1.062 b 1.067 a 1.065 ab 1.066 a empty table cell 0 75 150 225 empty table cellempty table cell Russett BurbankRussett Burbank 0 75 150 225 empty table cell 424 450 449 427 ns Russett BurbankRussett Burbank 194 80 75 200 69 194 54 202 ns ns Russett BurbankRussett Burbank 80 81 87 90 ns 1.072 1.071 1.070 1.072 ns Table 10. Influence of band phosphorus application on yields of potatoes grown in an Essexville loamy sand. Phosphorus Rate lb P2O5 Atlantic 2-3 1/4 Atlantic Total Yieldcwt/A cwt/A 0 75 150 225 empty table cell 288 297 301 275 ns 233 231 234 225 ns 1.079 1.073 1.076 1.078 ns Specific Atlantic Gravity Snowden Total Yieldcwt/A Snowden 2-3 1/4 Snowden Specific Gravitycwt/A cwt/A 215 210 182 187 ns 283 274 252 263 ns 1.075 1.076 1.073 1.071 ns Table 11. Influence of band phosphorus application on yields of potatoes grown in an Essexville loamy sand. Phosphorus Rate lb P205 Onawa y Total Yield cwt/A 0 75 150 225 empty table cell 293 245 268 272 ns Onawa y 2-3 1/4 cwt/A 228 178 201 213 ns Onaway Specific Gravity cwt/A 1.058 1.059 1.059 1.063 ns Superio r Total Yield cwt/A Superio r 2-3 1/4 cwt/A Superior Specific Gravity 203 219 252 257 ns 158 172 196 195 ns 1.064 1.064 1.064 1.066 ns Table 12. Influence of band phosphorus application on yields of potatoes grown in an Essexville loamy sand. Russett Norkotah 4-10 oz Russett Norkotah Specific Gravity Total Yield cwt/A Russett Burbank Russett Burbank 4-10 oz cwt/A Russett Burbank Specific Gravity Phosphorus Rate lb P2O5 0 75 150 225 empty table cell Russett Norkotah Total Yield cwt/A 272 261 289 270 ns cwt/A 140 132 157 141 ns 1.060 1.058 1.059 1.060 ns 232 263 229 239 ns 122 154 118 117 ns 1.064 1.068 1.064 1.066 ns Funding Federal Grant Colorado Potato Beetle Management 1991 Potato Research Report Ed Grafius, Beth Bishop, Walter Boylan-Pett, Judith Sirota, and Kaja Brix Department of Entomology, Michigan State University Summary Research in 1991 focused on 1) evaluation of genetically-engineered Bacillus thuringiensis potato plants for control of Colorado potato beetle, 2) trap crop systems to increase the efficiency of mechanical control of CPB, 3) comparison of flight behavior and flight muscle status between fed and starved adult CPB, 4) insecticides for control of CPB, 5) evaluation of Trigard for control of CPB, 6) design and evaluation of com/potato rotational systems for minimizing dispersal of postdiapause CPB, and 7) preparation and distribution of insecticide-resistance test kits. Research clearly showed that vacuuming early in the season and propane burning at vine kill could effectively control large larvae. Genetically- engineered Bacillus thuringiensis potato plants had significantly less CPB defoliation than non-transformed potatoes or a commercial cultivar sprayed with insecticide. Examination of transmission electron micrographs shows differences between flight muscles of fed and starved beetles. These differences indicate that beetles that have been starved for longer than 5 days have a reduced ability to disperse by flight. Insecticide evaluation studies showed that several insecticides, including Kryocide, Cryolite, Imidan & PBO and M-Trak gave adequate control of CPB larvae, reduced defoliation, and resulted in the highest yields. In addition, the insect growth regulator Trigard gave good control of CPB at three different rates. The presence of volunteer potatoes in a rotated com field reduced dispersal of overwintered CPB out of the com and into the new potato field. Reduced dispersal due to the volunteers could potentially reduce the number of CPB colonizing a new potato field, resulting in increased effectiveness of rotation as a management strategy. In addition, by discouraging dispersal, volunteer potatoes in a rotational crop may minimize the spread of insecticide resistance genes. Analysis of results of the resistance test kit indicates that resistance to most insecticides in CPB has increased dramatically in Michigan over the past few years. Introduction 1991 was a banner year for Colorado potato beetles. The very warm temperatures early in the year resulted in many beetles emerging from overwintering diapause before crops were up. There was much dispersal early in the year and flight was observed often. This dispersal may have spread insecticide resistance genes to new populations, resulting in many fields where CPB were uncontrollable with standard insecticides. Research in 1991 focused on finding new methods to control CPB. The insecticide resistance test kit developed in 1988 was available to growers for $10 through the M.S.U. Plant and Pest Diagnostic Laboratory. Two sets of insecticide evaluation trials were conducted. One set evaluated the insect growth regulator Trigard for control of CPB. In addition, potato plants that were genetically engineered by Montsanto with the Btt gene were tested in the field for control of CPB. Research also focused on non-insecticide methods of CPB control. Ways to increase the effectiveness and efficiency of mechanical vacuum cleaners were investigated by planting perferred "trap crops" to attract beetles. Studies on CPB dispersal were also continued. Furthur investigations into the effect of feeding on beetles’ flight behavior and flight muscle status were done. Also studied was the potential for volunteer potatoes to inhibit dispersal of overwintered CPB out of a rotated crop (last year’s potatoes) and into the current year’s potatoes, thus reducing the number of beetles colonizing the new crop. Funding for these projects was provided by the Michigan Potato Quality Grant and the National Potato Council Grant Program. Funding for studies in previous years was obtained from the North Central Regional IPM Grant Program. Additional support was provided by the respective agrichemical industries. Resistance test kits were developed with support from the Michigan Energy Conservation Program. Evaluation of trap crop systems to increase the efficiency of mechanical control of CPB. Trap crops were planted at the Smith Brothers Farm in Monroe Co. MI, on April 26, 1991. Eggplant and shallow or normal planted ‘Snowden’ potatoes were planted in four row plots at the border of a side-by- side crop rotation field. The number of CPB per plant was recorded weekly when the first CPB were found at the field. The eggplant and ‘Snowden’ potatoes were highly attractive as trap crops. Ten days after the adults had emerged there were 4.1 beetles per plant in the Snowden trap crop compared to 1.8 per plant, seven rows into the planting. Full evaluation of the trap crop system was not possible in 1991 due to emergence of beetles 3 weeks earlier than normal. The vacuum that was most extensively tested arrived late (on time for most years) and required extensive modifications to improve effectiveness. As a result, the trap crops were destroyed by the beetles before vacuuming was implemented and the beetles went on to invade the rest of the field. Research in 1991 clearly showed that vacumming early in the season and propane burning at vine kill could be effective (e.g. 88 and 79% contol of large larvae for two different crop vacuums and a burner, respectively). In addition to the direct effects of the vacuums on the adults and larvae, eggs were also removed or injured as the result of the movement of soil caused by the vacuum. Scanning electron micrographs of CPB eggs after vacuuming show severe abrasion to egg surface (Figure 1). The impact of this abrasion on eggs and small larvae has not been evaluated. It may be critical, however, since these CPB stages are the least effectively vacuumed and effects on these stages may allow longer intervals between vacuuming. Figure 1. Scanning electron micrographs of normal (top) and vacuumed (bottom) Colorado potato beetle eggs. Cracks on surface of normal egg are artifacts of the electron beam. In the vacuumed egg, severe surface abrasion and sand particles can be seen. Evaluation of genetically-engineered Bacillus thuringiensis potato plants for control of Colorado potato beetle. Transgenic and nontransformed seed potatoes were planted on 20 May at the MSU Montcalm Potato Research Station, Entrican, MI. Treatments included four Btt transformed minituber lines, a nontransformed minituber line, commercial ‘Russet Burbank’ seed, and commercial ‘Russet Burbank’ seed that was treated with Asana XL and PBO (0.05 #ai/A and 8.0 oz/A, respectively) weekly from 6 June through 8 August. Treatment effectiveness was determined by counting the total number of insects found on the center six plants of each treatment twice weekly from 19 Jun through 9 Aug. Plants were visually assessed for defoliation on 8 Jul. On 3 Oct all treatment rows were harvested and tubers were separated by size (A’s and B’s) and weighed. Slow plant emergence was characteristic of all transgenic plant types compared to the nontransformed minitubers and commercial cultivar. This slow growth rate was probably the result of inadequate vernalization of the transgenic seed. Commercial seed emerged sooner than the minitubers (transgenic and nontransformed) and plants were defoliated due to the extreme beetle pressure in mid May and early Jun. Significant differences in the number of egg masses, small larvae, large larvae, and adults were found between the transgenic and other plant types on the various sampling days. No significant differences in insect number or defoliation were found between transgenic lines (Table 1). The transgenic plants had significantly lower defoliation ratings than the nontransformed and commercial plant types. The small amount of defoliation of the transgenic plants was caused by beetles girdling stems. The low yield data of all treatments is the result of late planting, inadequate vernalization (transgenic plants), and the severe beetle pressure (nontransformed and commercial plants). Table 1. Defoliation Rating1 and Plant Yield1 From Transgenic and Non transformed Plants. Montcalm, MI. 1991 0.50 a 0.33 a 1.00 a 0.17 a 5.00 b 5.00 b 4.50 b Bttl9c Bttl6a Btt25a Bttl3d Nontransformed Commercial seed Comm Seed & Asana 1Means followed by different letters are significantly different (P5 to 10%, 2 = >10 to 25%, 3 = >25 to 50%, 4 = >50 to 75%, and 5 = >75 to 100% defoliation. 3.79 a 3.21 a 4.00 a 3.50 a 0.04 b 0.00 b 0.38 b The effect of CPB feeding on flight behavior and status of flight. Studies to compare the flight behavior of starved and fed beetles were conducted in the summer of 1991 in the field at the M.S.U. Collins Rd. Research Station. Three tests were done on the overwintered generation and one test was done on the summer generation. Beetles were starved or fed for varying lengths of time. Tests of flight behavior of starved and fed beetles were done at different times during the test. There appeared to be no differences between fed and starved beetles in flight behavior of overwintered CPB. On some days of the second test more starved beetles flew than did fed beetles. However, this was not a consistent trend. Preliminary analysis of the summer generation data indicates that starved beetles tended to fly more often than fed beetles on days 1, 4, and 10, but on day 15 there was no difference between the two treatments. The dorso-longitudinal flight muscles of fed and starved beetles were also examined to note any muscle degeneration, which might indicate a loss of the beetles’ ability to fly. Muscles of starved and fed overwintered beetles were analyzed via transmission electron microscopy. These analyses indicated that the muscles of starved CPB degenerate over time. Distinguishable differences occurred in the size and organization of flight muscles. This degeneration was progressive and the muscle of a starved beetle started to differ from that of a fed beetle after 5 to 10 days of starvation (Figure 2). The muscle of a fed beetle was well- organized, the fibrils are closely packed, with many mitochondria betwen the fibrils and virtually no space. The muscle of a starved beetle had markedly smaller fibrils, less organization, fewer mitochondria and many vacuoles. The smaller muscles of the starved beetle indicate that the ability of that beetle to fly may be reduced. Dispersal of starved beetles, therefore, may be limited once wing muscles begin to degenerate. Figure 2. Transmission electron micrograph of dorso-longitudinal flight muscles of Colorado potato beetles at 4500 x. Fed Beetle (left). Starved Beetle (right). Insecticide Efficacy Tests for CPB Control. Insecticide trials were conducted at the MSU Montcalm Research Farm in Entrican, MI. Potatoes (cv ’Atantic’) were planted on 25 and 26 April. Plots were three rows wide and 45 ft long and were Table 2. Mean number of Colorado potato beetles per plant over four sampling dates, and defoliation rating. Montcalm Co. 1991. MEAN NUMBER OF CPB OVER 4 SAMPLING DATES AND DEFOLIATION RATING TREATMENT EGG MASSESNUMBER OF CPB PER PLANT 1,2 ADULTS SMALL LARVAENUMBER OF CPB PER PLANT 1,2LARGE LARVAENUMBER OF CPB PER PLANT DEFOLIATION7 1,2 DEFOLIATION7 NUMBER OF CPB PER PLANT 1,2 21 JUNE 28 JUNE UNTREATED 11.75(1.11)a M-1 PLUS 1 gal/A 23.75(2.25)ab FOIL DF 1 lb/A 15.25(3.17)a FOIL DF 1.5 lb/A 3 23.00(1.68)ab FOIL DF 2 lb/A 24.75(3.99)ab 18.75(1.75)ab FOIL OF 1.45 qt/A FOIL OF 2.18 qt/A 20.00(2.80)ab FOIL OF 2.9 qt/A 15.25(4.35)a ECX-9124EH 1 lb/A 4,5 22.00(5.87)ab ECX-9124EH U lb/A 5 16.25(3.43)ab KRYOCIDE 11.5 lb ai/A 39.00(4.67) b TENAX 25 lb/A 16.00(3.03)a IMIDAN 1 lb/A 10.75(2.56) 14.25(4.70) 10.75(2.29) 10.50(3.80) 12.75(1.98) 9.50(1.56) 7.50(2.36) 10.50(1.66) 11.75(2.78) 9.00(1.08) 22.50(7.41) 11.00(2.94) 127.75(22.70) 182.00(41.12) 151.50(27.36) 163.50(32.92) 140.25(15.04) 134.50(15.50) 125.00(21.00) 86.75(22.79) 205.00(39.13) 157.25(42.14) 187.50(49.61) 107.75(21.04) 141.00(51.17) 141.50(18.12) 150.50(56.31)ab 100.50(17.69)ab 194.50(21.38)ab 152.00(14.09)ab 245.25(52.38)a 217.25(34.20)ab 171.25(15.78)ab 150.50(19.46)ab 178.25(19.66)ab 150.00(33.77)ab 84.00(10.03) b 150.25(27.20)ab 4.94 2.58 4.29 4.14 4.31 3.71 3.88 3.76 4.70 4.75 2.53 4.64 5.00 2.70 4.56 4.41 4.68 4.14 3.95 3.84 4.96 4.99 2.66 4.96 86.00 (9.10) b 132.75(11.34)ab empty table cell empty table cell 2.86 3.26 3.21 3.91 empty table cell + PBO 6 oz/A 6 CRYOLITE 9 lb/A empty table cell 14.50(2.40)a 19.75(3.57)ab empty table cell 13.75(4.73) 15.25(3.52) NS NS 1 2 3 4 5 6 7 Means followed by the same letter are not significantly different (Tukey's HSD, p > 0.05). Data transformed using ln (x + 1) for Tukey's HSD. Mean substituted for missing data from Plot 53 on 14 June for analysis. First treatment of ECX-9124EH was on 12 June. Mean substituted for missing data from Plot 18 on 7 June for analysis. Mean substituted for missing data from Plot 43 on 21 June for analysis. Rating: 1 = No defoliation; 2 = l%-25% defoliation; 3 = 26%-50% defoiation (some whole leaves eaten); 4 = 51%-75% defoliation (some stems bare); 5 = 76%-100% defoliation. NS Means within a column are not significantly different.______________________________________________ arranged in a randomized complete block design with four replications per treatment. The Tenax treatment was applied at planting in an 8 to 10 in band in the furrow. Foliar treatments were applied at 30 gal/acre and 60 psi with a hand­ held CO2 sprayer or a tractor-mounted boom sprayer. Foliar treatments were applied on 4, 12, 18 and 25 June. Plots were sampled by searching two plants from the middle row of each plot for all stages of CPB. Plots were sampled on 7, 14, 21 and 28 June. Plots were rated for defoliation on 21 and 28 June. Due to heavy CPB pressure and severe defoliation, the middle row of each plot was harvested on 31 July. Harvested potatoes were separated by size and weighed. Kryocide gave the best control of large larvae and had the lowest defoliation (table 1) and best yield (Tables 2 & 3). M-l Plus (M-Trak), Imidan & PBO and Cryolite gave fair control of large larvae, had low defoliation and good yields. The accelerated development of CPB in 1991 due to very warm weather early in the season, and the very high densities of beetles in this field (which resulted in complete defoliation of the field by the end of July) may have affected the performance of many of the insecticides. Table 3. Mean Potato Yield. Montcalm Co., MI. 1991. TREATMENT SIZE A1 SIZE B LBS PER 20 ROW FEET (S.E.) LBS PER 20 ROW FEET (S.E.) 1.13(1.13) a 13.25(1.61) be 5.75(1.09) a cd 9.88(2.70) b d 5.75(2.76) a cd 11.25(1.30) be 9.63(1.68) bed 1130(3.73) be 0.63(0.32) a 2.06(1.10) a UNTREATED M-l PLUS 1 gal/A FOIL DF 1 lb/A FOIL DF 13 lb/A FOIL DF 2 lb/A FOIL OF 1.45 qt/A FOIL OF 2.18 qt/A FOIL OF 2.9 qt/A ECX-9124EH 1 lb/A ECX-9124EH 1.5 lb/A KRYOCIDE 11.5 lb ai/A 19.13(235) b TENAX 25 lb/A IMIDAN 1 lb/A 3.13(1.81) a d 1.50(0.46) ab 5.25(1.44) ab 4.50(0.68) ab 3.75(0.83) ab 2.75(0.60) ab 3.88(0.55) ab 3.75(1.36) ab 3.00(0.79) ab 1.75(0.60) ab 2.50(0.74) ab 6.88(1.39) b 1.19(0.34) a + PBO 6 oz/A CRYOLITE 9 lb/A 9.75(7.96) b 12.13(1.43) be 5.50(1.21) ab 3.88(0.72) ab 1 Means followed by the same letter are not significantly different (Tukey's HSD on square root of weight + 0.5 transformation, p > 0.05). Control of CPB with Trigard. Trials using the insect growth regulator Trigard were conducted at two commercial potato fields in Bay County, MI. Potatoes (cv ’Onaway’) were planted on the Brian Hugo farm on 17 April and on the Jim Kryszak farm on 3 May, 1991. Plots were 14 rows wide and 60 ft long and were arranged in a randomized complete block design with four replications per treatment. Treatments included: no Trigard (control), and low (0.1251b A1/acre), medium (0.25 lb Al/acre), and high (0.375 lb Al/acre) rates of Trigard. Treatments were applied on 7 and 19 June with a tractor-mounted boom sprayer at 25 gal/acre and 40 psi. One or two plants per plot were sampled for CPB on 7 June (pre­ treatment sample). Four plants per plot were sampled on 13, 20 and 27 June, and on 2 July. Potatoes were harvested in each plot from two 10 ft sections of row on 19 August. Plots were assessed for defoliation on 2 July. Harvested potatoes were separated by size and weighed. In both fields, plots treated with Trigard had significantly fewer large larvae on all sampling dates than plots that were untreated (Figure 3). On some dates the numbers of adults per plant were significantly lower in Trigard-treated plots. There were no significant differences between treatements in the number of egg masses per plant. There was also no significant differences between plots treated with different rates of Trigard in the number of CPB of any stage. Defoliation was lower in treated than in untreated plots at both sites. Yields of treated plots were significantly higher than yields in untreated plots at both sites (Figure 4). Figure 3. Number of large Colorado potato beetle larvae per plant on plots treated with different rates of Trigard. Figure 4. Yield of potatoes treated with three rates of Trigard. Corn/Potato rotational systems for controlling dispersal of postdiapause Colorado potato beetle. Our ultimate aim in this research is to develop crop rotational systems that will prevent overwintered CPB adults from moving from the rotational crop (last year’s potato field) to the current year’s potatoes. The effect of volunteer (or intentionally planted) potatoes in a rotated com field on dispersal of overwintered Colorado potato beetle adults was evaluated. We hypothesized that the presence of potatoes in the com would keep the newly-emerged adult CPB in the com. Later, these volunteer potatoes and the beetles could be destroyed. If dispersal from the com to the potatoes were reduced, this would both reduce the size of the CPB population on the potatoes and prevent the spread of insecticide­ resistance genes to new sites. Plots were set up at two commercial fields in Montcalm County, Sandyland Farms (Larry Young) and Pleasant Valley Farm (Dan Evans). Plots were set up along the border of a side-by-side corn/potatoes rotation (i.e., the 1991 com field had been in potatoes in 1990, and visa versa). Plots were ca. 75 ft long and extended 20 rows into the com and potato field. Treatments were arranged in a randomized complete block design with four replications per treatment. Treatments included: A high density (1 per m2) of "volunteer" potatoes planted in the com, a low density (1 per 5 m2) of "volunteer" potatoes planted in the com, and no volunteers. At the Sandyland site the low-density volunteer treatment was not included. The central portion of each com plot was searched for beetles. When found, beetles were marked on the elytra and then released in the center of the plot. The color and pattern of the mark indicated the date and plot number of the release. Besides searching the central portion of each com plot for marked and unmarked beetles, the first three rows of each potato plot-was searched for marked beetles and unmarked adult beetles were counted on two potatoes per row for the first 10 potato rows in each plot. The spring of 1991 was very warm and emergence of adult overwintered CPB occurred very early, in most cases before either potatoes or rotational crop emerged. Lots of CPB flight was observed, so much dispersal probably occurred early, before the emergence of the corn or potatoes. Consequently, we did not find fewer beetles found in potatoes opposite com plots with volunteers than in potatoes opposite corn plots without volunteers, as we expected. However, both the number of unmarked adult CPB found in corn (Figure 5) and the percent of released beetles recaptured in corn (Figure 6) was higher for corn plots with volunteers than for corn plots without volunteers. This was true for both sites. These data indicate that the presence of volunteer potatoes in a rotated crop, such as corn, may discourage newly-emerging overwintered CPB from moving from the corn to the new potatoes. Of marked beetles that were recaptured, a higher proportion was found in the potatoes (rather than in the corn) when the beetles were released into corn plots without volunteers. This, and other results, suggest that lack of food (potatoes or solanaceous weeds) in the rotated crop may contribute to dispersal of overwintered CPB, perhaps over fairly long distances. This dispersal may lead to colonization of distant potato fields and the spread of insecticide genes, thus reducing the effectiveness of crop rotation as a management strategy for CPB. These preliminary investigations into methods of reducing dispersal of CPB out of rotated fields are encouraging. However, there were several problems that probably reduced the effectiveness of volunteers in preventing dispersal. First, as mentioned above, an early, very warm spring resulted in beetles emerging and dispersing before the corn, potato crop or volunteers. A good amount of dispersal had already occurred before our experiments began. Second, at both sites the corn field was cultivated shortly after our experiments began. The majority of the volunteer potatoes in the corn were destroyed by this cultivation. Therefore, the volunteer potato density was much lower than we originally planted. To correct for these problems, we did a series of experiments at the M.S.U. Research Farm. Plots (4 m x 4 m) were set up in a corn field. Potted potato plants were buried within these plots to simulate volunteers. A row of 9 potted potato plants was planted in the ground 0.5 m from the corn plot to simulate the potato field. Treatments included a low and high density of volunteers, and no volunteers. Marked beetles were released in the center of the corn plot. Both the corn plot and the row of potatoes were searched for marked several times from 4 to 48 hours after the beetles were released. Preliminary results of these experiments show that Figure 5. Number of adult CPB found in rotated com plots with or without volunteer potatoes. Figure 6. Proportion of marked CPB released into com plots with or without volunteer potatoes that were recaptured in the com on June 4. volunteers in the com were very effective in preventing the beetles from dispersing to the row of potatoes. Distribution of on-farm, insecticide resistance test kit. This kit lets growers test beetles from their potato fields for resistance to four insecticides (representing the four major types of insecticides) and an insecticide-synergist combination. The kit has been in use since 1988. This year the kit was distributed through the M.S.U. Plant Pest Diagnostic clinic. The charge for the kit was $10 and was used to help defray costs of production and distribution. Results of these tests for the past few years indicate that insecticide resistance in CPB has quickly become widespread in Michigan. A comparison of tests results since 1988 of beetles in individual fields in Montcalm County was made by Don Smucker (Figure 7). These results show the increase in resistance to and resulting loss of effectiveness of all insectcides in the kit (except for Imidan, which was ineffective in these fields to begin with) over the past four years. Figure 7. Results of insecticide resistance tests on Colorado potato beetles in four fields in Montcalm County, Michigan. Results are from years 1988 to 1991. 1991 NEMATOLOGY REPORT Funding Federal Grant/MPIC F. Warner, G.W. Bird, J. Davenport, C. Chen and B. Mather Department of Entomology Michigan St. University Eight trials were conducted in 1991 to further investigate the role of root-lesion nematodes, Pratvlenchus sp., in Michigan potato production. Two nematicide, 3 variety and 3 crop rotation studies were completed or are in various stages of completion. The rotation studies are part of the USDA Special Grant to study integrated crop management: nitrogen and nematode management effects on potato yield, quality and water quality. Fall Nematicide Trial The objective of this trial was to evaluate the effectiveness of an experimental compound, N869, for root-lesion nematode control in potatoes (Table 1). N869 was applied preplant and incorporated at 3 rates. Vapam was applied at 2 rates. Both materials were applied in the fall of 1990. Nematode samples were collected 4 1990 to harvest, Sept. 11, 1991. The times from Oct. 24, applications of Vapam resulted in the highest total yields although there were no difference between the 2 rates. No statistical yield differences were observed between the 3 rates of N869 and the untreated control. However, N869 applied at the 2 highest rates reduced the numbers of root-lesion nematodes recovered from root tissue and soil on June 26 when compared to the low rate and the control. Vapam resulted in excellent nematode control, means of less than 1 nematode per gram of root tissue were recovered on the June 26 sampling date. Granular Nematicide Trial The primary objective of this study was to compare different application methods of Mocap and Thimet and the effectiveness of fosthiazate for nematode control in potatoes (Table 2). Virtually no yield differences were observed at harvest between treatments. Root-lesion nematode counts were very low throughout the growing season with almost no differences between treatments observed. Variety Trials Three variety trials were conducted in 1991, two field experiments and one greenhouse study. The greenhouse study and one of the field trials were microplot evaluations and these experiments have not been completed. The results of the other field trial are presented in Table 3. The objective of this study was to compare the responses of 3 potato varieties in plots left untreated and in Temik-treated plots. Although Temik 15G is no longer registered for use in potatoes, it was utilized in this trial to provide nematode (and insect) control. The application of Temik (3.0 lbs a.i./A) did not result in the recovery of statistically lower means of root-lesion nematodes/g root tissue in any of the 3 varieties on July 2. However, the numbers of nematodes recovered in the soil at harvest were lower in Onaway plots and Russet Norkotah plots where Temik had been applied. Temik resulted in a favorable yield response for all 3 varieties. Snowden produced the highest yields in the trial, yields of Russet Norkotah were the lowest. Rotation Trials Three crop rotation experiments were conducted in 1991. One trial, located at the Experimental Farm in Montcalm Co. was completed in 1991. Two other trials, one at the Experimental Farm and the other at the Jon Haindl Farm in Cooks are long term studies that were established in 1991. The primary objective of the crop rotation trials is to evaluate a broad range of potential potato production system rotation crops that will alleviate potato tuber yield and quality losses caused by the joint action of the root-lesion nematode, Pratvlenchus penetrans. and the Verticillium wilt fungus, Verticillium dahliae. The experimental design of the long term study in Montcalm Co. is shown in Table 4. Three crops were grown at this location in 1991, potato (Russet Burbank), oats and alfalfa. There were no differences in the number of lesion nematodes recovered in root tissues and surrounding soil of the 3 crops on July 2 (Table 5) . However, on Sept. 11, fewer nematodes were recovered from potato roots and soil than the other 2 crops. As expected, both oats and alfalfa were good hosts for P. penetrans. Five crops were grown in the trial located at the Haindl Farm in the U.P., potato (Superior), oats, alfalfa, june (red) clover and yellow sweet clover. All the crops appeared to be hosts for the lesion nematode, although fewer nematodes were recovered from potato roots and soil on July 8 than from roots and surrounding soil of the other crops investigated (Table 6). However, the means were not statistically different except where oats and alfalfa were intercropped compared to all the other crops but june clover. On Oct 7, the two species of clover supported higher populations of Pratvlenchus sp. than either alfalfa or oats/alfalfa. Clovers are considered good hosts for root-lesion nematodes. A 3-year rotation study was terminated in the fall of 1991. Five crops were utilized, potato (Superior), corn, sudax, sweet clover and alfalfa. Potato was the only crop grown in 1991, the other crops had been grown for 1 or 2 years prior to potato (Table 7). £. penetrans counts ranged from 85-229 nematodes/g root tissue and 100 cm3 soil on June 28. Two years of clover or alfalfa followed by potatoes resulted in the highest yields. Yields were not high, ranging from 154 cwt/A to 302 cwt/A. However, no nematicides were used and nematode counts were considered high. The following trends can be observed in Table 7. Although, the differences were not significantly different, two years of corn or sudax followed by 1 year of potatoes resulted in lower yields in 1991 than 1 year of corn or sudax followed by 2 years of potatoes. However, 2 years of sweet clover or alfalfa followed by potatoes in 1991 resulted in significantly higher yields than 1 year in either commodity followed by potatoes for 2 years. Table 7 does not include the 1990 potato yield data. Yields ranged from 232 cwt/A (sudax/potato) to 270 cwt/A (corn/sudax) in 1990. Further analyses were conducted to compare potato yields from 1990 following 1 year in a rotational crop to yields in 1991 following 2 years in the respective crops. Two years of corn and sudax followed by a potato crop resulted in significantly lower potato yields than only rotating for 1 year with corn or sudax. Two years of sweet clover produced a statistically significant potato yield increase when compared to 1 year of sweet clover followed by potato. There was no significant difference between growing alfalfa for 1 or 2 years between potato crops. Therefore, it's very apparent that cropping sequences will affect potato yields. Root-lesion Nematode Population Root-lesion Nematode Population Root-lesion Nematode Population Root-lesion Nematode Population Potato Yield 10/24/90 soil 591 a2 82 a 77 a 92 a 42 a 124 a 5/2/91 soil < 1 b < 1 b 5 ab 11 ab 7 ab 12 a 6/26/91 root & soil 1 c < 1 c 138 a 68 b 48 b 142 a 9/11/91 soil 1 c < 1 c 29 a (cwt/A) 435.1 a 451.8 a 236.4 bc 24 ab 261.0 bc 14 b 30 a 287.2 bc 209.4 C 1. Metham 2. Metham 3. N869 29.26 G 4. N869 29.36 G 5. N869 29.34 G 6. CK 75 gal/A Broadcast 150 gal/A Broadcast 37.5 lb/A P.P.l. 75 lb/A P.P.I. 150 lb/A P.P.I. no treatment Table 1. Montcalm Potato Nematicide Fall Application Test in Montcalm, MI in 1991 Treatment Application Note: 1. The mean population of root-lesion nematode is presented as nematodes per 1.0 gram root tissue and nematodes per 100 cm3 soil. 2. Means followed by the same letter are not significantly (P=0.05) different according to the Duncan's Multiple Range Test. Table 2. The Granular Nematicide Trial in Montcalm Research Farm AP Nematicide Treatment in 1991 1. CK without AP application in 1991 2. Temik 15G 3.0 lb ai/A IFF 3. Vydate 2L 3.0 lb ai/A 12” band 4. Mocap 10G 3.36 oz/1000 ft 5-7' band behind planter shoe, before closing discs 5.Mocap 10G 3.36 oz/1000 ft 5-7" band before planter shoe, behind closing discs 6. Mocap 10G 3.36 oz/1000 ft 5-7" band behind shoe, before discs Phorate 20G 3.46 oz/1000 ft ISPF 7. Mocap 10G 3.36 oz/1000 ft 5-7" band before shoe, behind discs Phorate 20G 3.46 oz/1000 ft ISPF 8. Mocap 10G 3.36 oz/1000 ft 5-7" band before shoe, behind discs Phorate 20G 3.46 oz/1000 ft 5-7" band before shoe, behind discs Root-lesion Nematode Population Root-lesion Nematode Population Root-lesion Nematode Population 5/14/91 soil 3 a < 1 a < 1 a < 1 a 6/26/91 root & soil 7 a 3 b 1 b 2 b 9/6/91 soil 9 a 1 c 2 bc 5 abc Potato Yield (cwt/A) 263.5 ab 331.5 a 295.5 ab 276.8 ab < 1 a < 1 b 2 bc 298.2 ab < 1 a < 1 b 5 abc 291.1 ab 2 a < 1 b 7 ab 224.1 b < 1 a < 1 b 4 abc 258.9 ab 9. Mocap 20G 90 lb/A Broadcast/Incorporate 10. Fosthiazate 6 lb ai/A 12" band 12. Fosthiazate 8 lb ai/A 12" band 12. Fosthiazate 12 lb ai/A 12" band 2 a 1 a 3 a < 1 a < 1 b < 1 b 1 b 4 ab 4 abc 3 bc 1 c 5 abc 297.4 ab 303.2 ab 282.4 ab 295.7 ab Table 3. Potato Variety Trial in 1991 Variety Aldicarb Root-lesion Nematode Population Root-lesion Nematode Population Root-lesion Nematode Population 5/15/91 soil 7/2/91 root 9/1/91 soil Tuber Yields (cwt/A) 241.4 c 279.1 b 194.4 d 72 a 5 c 76 a 1. Onaway 2. Onaway 3. Norkotah Russet 4. Norkotah Russet 5. Snowden 6. Snowden - + - + - + 56 a 58 a 64 a 55 a 52 a 50 a 18 b 3 b 44 ab 6 b 17 b 3 b 5 c 247.8 c 40 b 11 bc 302.2 b 340.7 a 1. The root-lesion nematode population is presented as nematodes per 1.0 gram root tissue and nematodes per 100 cm3 soil. 2. Means followed by the same letter are not significantly (P=0.05) different according to the Duncan's Multiple Range Test. Table 4. Experimental Design of 1991-2000 Crop Rotation Montcalm Component Tmt 2 Tmt 4 oats alf Potato alf Tmt 5 oats soy alf Potato alf Tmt 3 Tmt 1 Potato alf alf Potato Potato alf Potato Potato Potato Potato Potato Potato Potato Potato Tmt 6 oats soy kid Potato alf Potato Potato Potato Potato Potato Potato alf Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Potato Tmt 9 Tmt 7 Tmt 8 oats oats oats soy soy soy kid kid kid wh wh wh pea alf pea Potato alf wh alf Potato alf alf Potato Potato Potato alf Potato Potato Potato Potato Potato Tmt 10 oats soy kid wh pea wh soy alf Potato alf Potato Potato Potato Potato Year 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 Table 5. 1991-2000 Crop Rotation Montcalm Component - 1991 Data Treatment 1. Potato 2. Alfalfa 3. Alfalfa 4. Oats 5. Oats 6. Oats 7. Oats 8. Oats 9. Oats 10. Oats Root-lesion Nematode Population Root-lesion Nematode Population Root-lesion Nematode Population 5/13/91 soil 8 a 7 a 11 a 7 a 7 a 9 a 8 a 6 a 7 a 6 a 7/2/91 root & soil 9/11/91 root & soil 118 a 85 a 115 a 138 a 125 a 120 a 123 a 131 a 85 a 146 a 21 c 183 b 176 b 269 ab 241 ab 318 a 369 ab 246 ab 224 ab 205 b Table 6. 1991-2000 Crop Rotation UP Component - 1991 Data Treatment 1.Potato 2.Oats 3.Alfalfa 4.June Clover 5.Yellow Sweet Clover 6.Oats & Alfalfa Root-lesion Nematode Population Root-lesion Nematode Population Root-lesion Nematode Population Root-lesion Nematode Population 5/28/91 soil 43 a 29 a 39 a 27 a 37 a 35 a 7/8/91 root+soil 74 b 248 b 132 b 337 ab 279 b 568 a 10/7/91 root 10/7/91 soil empty table cell 26 c 56 ab empty table cell 6 b 36 bc 12 c 32 bc 65 a 55 a 47 a 20 b Table 7. 1989-1991 Crop Rotation Trial - 1991 Data 1989 1990 1991 Potato Potato Potato Potato Potato Rye Potato Potato Corn Potato Corn Corn Potato Potato Sudax Potato Sudax Sudax Potato Potato Clover Potato Clover Clover Potato Alfalfa Potato Alfalfa Alfalfa Potato Root-lesion Nematode Population Root-lesion Nematode Population Root-lesion Nematode Population 5/21/91 soil 9 c 28 b 12 bc 54 a 13 bc 12 bc 16 bc 9 c 24 bc 13 bc 6/28/91 root & soil 106 cd 143 abcd 85 d 229 a 191 abc 132 bcd 201 ab 144 abcd 154 abcd 146 abcd 8/20/91 soil 144 a 145 a 90 ab 71 b 127 ab 70 b 138 a 67 b 118 ab 67 b Potato Tuber Yields (cwt/A) 203.8 ab 217.1 ab 228.1 b 176.8 ab 184.4 ab 154.5 a 209.0 ab 301.8 c 214.5 ab 288.8 c Funding Federal Grant POTATO STORAGE MANAGEMENT: Atlantic vs. Snowden Potatoes harvested in the fall of 1990 were compared for storage response in the MSU potato storage research facility. Varieties evaluated were Atlantic and Snowden (formerly W855). The goal was to store the potatoes for an extended season and to monitor their response to the storage management strategy used in previous research on Atlantic potatoes. Any differences in storage response by variety can be a guide for managing a commercial potato storage. Storage System The MSU potato storage research facility is a set of bins, each measuring 8’ x 8’ x 18’ high. Two of the storage bins were installed during the summer of 1990 in a commercial potato storage facility at Bishop Potato Farm (Pinconning, MI). A floor plan of the storage facility is shown in Figure 1. Ventilation System - Each potato storage research bin has an independent air handling system capable of maintaining a desired storage environment for that bin. Each fan is capable of providing upto 3 cfm of air per cwt of potatoes stored in the bin. The ventilation specifications are given in Table 1. The intake air is drawn from outside through a common insulated fresh air manifold. The exhaust air is directed into the headspace of the pile in the commercial bin. Figure 1. Floor plan of the potato storage research facility. Control System - Each ventilation system is controlled using a 656 FANCOM* environmental control computer. The computer controls fresh air and recirculation air volume and humidifying and heating devices. Control changes are made based on feedback from the sensors that are placed in the ventilation and in the pile as illustrated in Figure 2: • temperature sensors at three foot increments within the pile • temperature and relative humidity of ventilation air • temperature and relative humidity of recirculation air Storage Management The potatoes were harvested on September 26,1990. Pulp temperatures were 67°F for the Atlantic potatoes and 57°F for the Snowden potatoes. Potato samples were taken weekly from the top of the pile, and from 3 levels within the pile. These samples were analyzed for fry color and for sucrose and glucose sugar content. Samples were also taken monthly for analysis of changes in wound healing ability and resistance to decay by Fusarium sambucinum. Authors are Roger Brook, professor and Robert Fick, graduate research assistant, Agricultural Engineering Department, Michigan State University, and Ray Hammerschmidt, professor, Botany and Plant Pathology Department. • Trade names are used solely to provide specific information. Mention of a trade name does not constitute a warranty of the product by the authors or by Michigan State University or an endorsement of the product to the exclusion of other products not mentioned. Table 1. Details of potato storage research ventilation system. empty table cell Capacity (cwt) Ventilation rate (cfm/cwt) Slot height (inch) Slot area (sq. ft) Slot velocity (ft/min) Lateral size (sq. ft) Main size (sq. ft) Atlantic Snowden 370 2.2 0.5 0.69 1180 1.2 24 345 2.8 0.5 0.69 1400 1.2 24 After the storages were filled, the potatoes were controlled at a temperature of 60°F for suberization and pre­ conditioning. The cooling phase began on October 31, 1991. The control system was programmed to reduce the average potato pile temperature by 0.2°F per day until the desired storage temperature was attained. The fans were set to run for 6 hours of every 12, with the control computer determining the amount of fresh air to use to achieve the desired amount of cooling. Atlantic potatoes were cooled to 50"F and Snowden potatoes to 45°F. The potatoes in both bins were treated with sprout inhibitor on November 12, 1990. The cooling phase was complete on January 22, 1991. During the holding phase, the control system was programmed to run the fan for 3 hours of every 12 to maintain the desired storage temperatures. Sampling for sugar analysis and for decay resistance continued. The potatoes were marketed on April 9, 1991. Environment Control - An analysis of the data for potato temperatures and for ventilation air relative humidities is presented in Table 2. The data shows an adequate environment control in both bins. The controller was set to maintain the following values or differences: • difference between any two pile temperature sensors of 2°F • difference between average pile temperature and ventilation air temperature of 4°F relative humidity of 90% • Figure 2. Detail of ventilation system and sensor placement within potato storage research bins. Potato Quality - The sucrose and glucose sugar contents for the potato samples during the storage season are shown in Figure 3 for the Atlantic variety and in Figure 4 for the Snowden variety. There was no significant difference in the sugar contents between the levels in any storage research bin. All samples during the storage season had acceptable fry color. Table 2. Controller performance for average pile temperature and inlet air relative humidity. (empty cell) Atl ant ic Sno wd en Pile temperature difference (°F) Plenum-Pile; temperature difference (°F) Plenum-Pile max temp difference ˚F) Inlet air relative humidity (%) 03 (0. 5) 0.5 (0. 5) 3.1 05 (0.5 ) 1.0 (0.6 ) 3.6 2 (3) 3 (2) * numbers in parenthesis are standard deviations of the averages Both the Atlantic and the Snowden varieties exhibited near constant ability to suberize and to restrict dry rot development. However, after January, the ability of both varieties to carry out these two functions declined. Overall, Snowden appeared to have somewhat more resistance to Fusarium than did Atlantic. The level of resistance, however, was not great enough to prevent rot development Snowden also appeared to have somewhat greater wound healing ability. It appears from limited observations that the Snowden variety potatoes sprouted somewhat earlier than did the Atlantic variety potatoes which would indicate that they should be managed with a faster cooling rate. Recommendations The Snowden variety potatoes stored at 45°F appear to respond to storage management in a manner similar to the Atlantic variety potatoes stored at 50°F. Chip color and sugar analysis were acceptable throughout the duration of the storage. We believe uniform and gradual temperature changes are important for maintaining potato color and quality through extended storage. It is important to use a temperature control system that will maintain the temperature of the cooling air above 42-45°F. It appears that re-conditioning will not normally be necessary, but the feasibility and strategies for re-conditioning of Snowden variety potatoes need to be evaluated. Cooperative Extension Service programs and materials are available to all without regard to race, color, national origin, sex, handicap, age or religion. Michigan State University, US. Department of Agriculture and counties cooperating. MSU Is an Affirmative Action / Equal Opportunity Institution. Figure 3. Potato sample sugar analysis for Atlantic variety potatoes, 1990-1991. Figure 4. Potato sample sugar analysis for Snowden variety potatoes, 1990-1991. PACKAGING ALTERNATIVES FOR LIGHT USERS OF TABLESTOCK POTATOES Funding Federal Grant A Summary of Mall Intercept Interviews Mary D. Zehner1 Mall intercept interviews were conducted with consumers of fresh potatoes in March, 1990 in metropolitan Detroit, Michigan. While the overall goal of the study was to suggest how the Michigan potato industry compete more effectively in the marketplace for tablestock potatoes (especially for round, white potatoes), specific objectives included: * * * * To evaluate light potato users’ rating of six packaging options for buying fresh potatoes (three varieties in bulk, tray pack, three- and five-pound bags). To evaluate consumers’ variety and size preferences for three potato varieties. To examine consumers’ level of awareness, and reasons cited for the greening (glyco-alkaloids) on potatoes skins. To learn present use patterns and selection criteria for light users (potato size, quality, variety, etc.). The research was conducted through the Agricultural Experiment Station (AES) of Michigan State University and funded as a part of the Potato Research Special Federal Grant. METHODOLOGY Mall intercept interviews were conducted with light users of fresh potatoes at two mall sites in early March 1990. Mall intercept interviews are a quantitative survey method used to follow-up of focus group interviews carried out in December, 1989. 1. Background questions were asked on purchasing patterns and preferences for potatoes (size and type package bought, size, etc.) 2. Participants evaluated a display with 6 packaging options for potatoes. All three potato varieties included in the study (Superior, Russet Norkotah and Russet Burbank) are readily available in Michigan supermarkets during the winter months. Two of the six options displayed were packaging alternatives readily available in Michigan supermarkets...unpackaged, bulk Russet Burbank potatoes and a 5-pound bag of U.S. No.l all-purpose potatoes. Average current retail prices were used during the time period of the study but the prices did not include any "specials." The information provided about varieties was typically used for bags and/or signs for potatoes..."all-purpose potatoes" rather than listing the varietal name Superior, or "Russet potatoes" rather than Russet Norkotah. The packages in the display were rotated after each ten participants in order to avoid positional bias. 3. If growers move in the direction of providing consumers with more closely sized potatoes, the question arises, "What size(s) potatoes of which varieties would best meet the needs of consumers?" Participants were to select their top choice among the two sizes of Russet Burbanks and three sizes of both the Superiors and Russet Norkotahs. The potatoes were displayed in a matrix with six to twelve potatoes (more of the small potatoes and fewer of the large potatoes), each in an individual tray. No retail price or variety identification was provided. The trays displayed were rotated to avoid positional bias. 4. What are consumers’ level of awareness regarding seeing greening on potato skins and the perceived cause of this greening? Long a problem for growers, greening is the mam reason for packaging round, white potatoes in paper. 1 Department of Agricultural Economics, Michigan State University, E. Lansing, MI 48824-1039. Chi-square analysis was carried out on all the responses versus the ages of participants, income level, size of household, and households with and without children under 18 at home. Comparisons are reported where the differences were at the 5 percent level or higher in the chi-square tests. FINDINGS Mall intercept interviews were conducted in a middle class shopping mall where the criteria for participation was that shoppers bought 1- to 10-lbs. of fresh potatoes in an average month. Data on the 190 participants revealed: 84% were female; about one fourth were in each of the following age groups: 18 to 34 years, 35-44 years, 45 to 64 years and 65 and older; half the respondents were in one or two member households; 38% had children under 18 at home; and half the households had women employed outside the home. Forty-one percent had yearly incomes between $20,000 to $45,000 while 22% had incomes over $45,000. Microwave oven ownership was 89% and two-thirds of the microwave owners reported cooking potatoes in their microwave ovens. 1. Purchase Patterns - Based on the 190 respondents, 88% purchased tablestock potatoes in bags, 46% from unpackaged, bulk displays and 7% from a tray pack at least once during the past six months. A second question revealed that three-fourths of the participants bought potatoes in bags more often than any other type of packaging while 21% most often bought from a bulk display. The majority bought their potatoes in net or mesh bags (51%) followed by paper bags (34%). Slightly more of these 167 respondents who bought potatoes in bags, reported purchasing potatoes in the 10-lb. bags (52%) than in 5-lb. bags (41%). The majority indicated they usually bought potatoes in a net or mesh bag (51%), a type of bag not generally used by Michigan shippers. Just under half (46%) of the 190 respondents reported purchasing potatoes from an unpackaged, bulk display during the past six months. Participants were asked how satisfied they were with the way they usually bought potatoes. Those buying bulk, unpackaged potatoes reported being the most satisfied...followed by those buying bagged potatoes while buyers of the tray wrap reported being least satisfied. 2. Packaging Alternatives - These light users of potatoes clearly favored the more traditional alternatives for buying potatoes over the newer options, as shown in Table 1. Almost half of the participants reported they would be most likely buy Russet Burbanks (9 oz) from the bulk display even though they were more expensive than the bulk all- purpose potatoes ($.49 versus $.39 per pound), plus the Russet Burbank potatoes had rhizoctonia (black spots) on the skin surface. This was followed by 17% who would buy the 5 lb. bag of all-purpose potatoes (Superiors). Very few favored the tray wrap of three Russet Norkotahs (4 percent) and there appears to be a limited market for this specialized pack. Both the bulk displays (9 oz. Superiors and 9 oz. Russet Burbanks) were most popular as the second choice. The one potato pack they would be least likely to buy was the tray wrap with the three Russet Norkotahs. Participants were asked to report the reason for their choice of a particular potato package. A common thread throughout the responses was "size of the potatoes.” The type of package and variety were also mentioned. Because of the keen interest in the size of potatoes as the reason for selecting a particular packaging option, many Michigan potatoes are at a disadvantage (from shoppers’ perspective) since they are sold predominantly in paper bags which do not allow for inspecting size and quality before purchase. 3. Potato Size Preferences - What specific size(s) of potatoes would best meet the needs of light potato users? Three varieties (Superior, Russet Burbank and Russet Norkotah) were displayed with small (4 to 5 oz.), medium (6 to 7 oz.) and large potatoes (9 to 10 oz.). From outward appearance, the Norkotah is a russet type potato very similar to the shape to the Burbank, but with a darker netting. Although the study was directed at round, white potatoes, the Michigan acreage of Russet Norkotahs is increasing. Hence it was meaningful to learn how Russet Norkotahs are perceived by consumers as compared with the Superiors and Russet Burbanks. Potato Packaging Respondents Most Likely, Least Likely to Buy (Six Packaging Options, with Current Prices) Table 1. Display First Choice Most Likely to Buy First Choice Second Choice Most Likely to BuySecond Choice Most Likely to Buy Most Likely to Buy Least Likely Least Likely to Buy to Buy Number Percent Number Percent Number Percent Bulk - 9 oz Russet Burbank ($.49/lb) 5 lb bag, U.S. No 1 - Superior ($1.59) 3 lb bag, 4-6 oz Russet Norkotah ($1.29) Bulk Superior (9 oz) ($.39/lb) 3 lb bag, 2 1/4 - 2 3/4 Superior ($1.19) Tray pack - (8 oz) Russet Norkotah ($.99) No response empty table cell 87 33 25 21 17 7 - - 190 46% 17 13 11 9 4 100% 47 43 30 29 23 17 1 190 23% 16 12 25 15 9 - 100% 8 25 27 30 20 77 3 190 4% 13 14 16 11 41 1 100% Table 2 reveals that the Russet Burbanks were again the preferred choice as 30% favored the large Burbanks and 24% the medium size Burbanks (sometimes called "strippers”). This was followed by large Superior and the large Norkotah potatoes. Although there were only two sizes of Russet Burbanks displayed, they commanded over half the first choices for buying while the three sizes of both the Russet Norkotahs and Superiors were the combined first choices of 25 percent and 21 percent respectively. Table 2. Respondents’ Choice of Potato Variety and Size to Buy (No Price Information or Variety Names are Provided) Variety Size First Choice Second Choice Russet Burbank Russet Burbank Superior Russet Norkotah Superior Russet Norkotah Superior (9-10 oz) (6-7 oz) (9-10 oz) (9-10 oz) (6-7 oz) (6-7 oz) (4 oz) Russet Norkotah empty table cell empty table cell (4 oz) 30% 24 13 10 8 7 4 4 100% 24% 21 15 8 12 10 2 8 100% If one considers the participants first choice preferences by size of potatoes, then the large potatoes (for the three varieties) were the choice of over half (54%) while 39% favored the medium size potatoes (6-7 oz). Clearly there is a very limited market for the small potatoes as only 8% selected them as their first choice. The most popular methods for preparing any variety of potato were baking and mashing, with the exception of the small Superiors. The question arises whether the darker netting on the Norkotah potatoes had an adverse effect on participants’ perception of the potatoes. Perhaps respondents felt the Norkotahs, because of the dark color due to the netting, appeared dirty. It should be noted that the large Burbanks did have rhizoctonia (black spots) on the skins. Apparently the more familiar Burbanks, when placed next to the Norkotahs, were strongly favored. 3. Greening of Potatoes - Almost nine out of ten (89 percent) respondents reported, "Yes" to the question "Have you ever seen fresh potatoes that have skins with a greenish tinge?” Those over 34 years old were more likely than the younger respondents to have seen this greenish tinge (glyco-alkaloids). Most of the respondents reported clearly incorrect reasons or indicated that they did not know what causes greening in potatoes. Half (50%) believed greening was caused because the potatoes were "not ripe"/"premature harvesting," 24% reported they "don’t know or had no opinion" and 19% mentioned "other" causes (such as soil/dirt, chemicals, frost or cold, oxidation, it’s normal, fungus or bacteria, pollution, radiation, pigment etc.) Bananas, tomatoes and apples are green before they ripen, but a large proportion of these respondents incorrectly associate the greening of potatoes with immaturity. Very few were even on the right track as to the cause(s) of greening of potatoes. About 14 percent believed it was caused by sunlight or the potatoes growing close to the surface of the ground (a possibility), and only three percent reported that the greening could be related to fluorescent or store light. Two percent believed green potatoes weren’t good for you/poisonous, but didn’t know the cause. SUMMARY...Where Do We Go From Here This report summarizes the findings from the mall intercept interviews conducted with light users of potatoes in metropolitan Detroit, Michigan in early March 1990. 1. Michigan producers must become more customer-oriented in order to maintain their share of the tablestock potato market by better meeting the needs of a growing number light users of fresh potatoes (i.e., shoppers who want to see the potatoes in bags, have smaller households so need smaller units of purchase, the option of selecting the exact number of potatoes needed, and improved quality and more closely sized than U.S. No. 1 potatoes). An increasing number of consumers are less price-driven and more interested in convenience and value of products bought. 2. For in-home use of fresh potatoes, the potential appears greatest for baked potatoes. This is related to more convenience-oriented shoppers and increased ownership and use of the microwave oven to speed up food preparation. Findings from the mall intercept interviews revealed a strong preference for Russet Burbanks over the Russet Norkotahs potatoes. In the short run, it is important to carry out consumer sensory tests to learn how the perceived attributes of the Russet Norkotah variety compare with the Russet Burbanks and Superiors (shape, color of skin, appearance of skin, texture and taste). The findings may provide direction for marketing of Russet Norkotahs and Superiors. 3. There is a large educational gap between consumers’ level of awareness and their understanding of the cause of greening of potato skins. It is important to develop an promotional/educational program (especially targeted toward younger consumers) to clear up the confusion and misinformation about what causes the greening of potatoes, as well as how to buy and store potatoes to maintain quality and minimize greening.