INFORMATION T O U S E R S This dissertation was produced fro m a m ic ro film copy of th e original docum ent. While th e most advanced technological means t o photograph and reproduce this d o cu m e n t have been used, the quality is h e a v ily dependent upon the q u a lity o f the o rig in a l submitted. The fo llo w in g explanation of techniques is p ro v id e d to h e lp you m arkings or patterns w hich may appear on th is re p ro d u c tio n . 1. understand The sign o r "ta rg et" for pages a p p a re n tly lacking from th e docum ent photographed is "Missing Page(s)". I f it was possible to o b ta in th e missing page(s) or section, they a re spliced in to the film along w ith adjacent pages. This may have n e ce ssita te d c u ttin g thru an image and duplicating adjacent pages to insure y o u com plete c o n tin u ity . 2. 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The m a jo rity of users indicate th a t th e textual content is o f greatest value, however, a somewhat h ig h e r qualitv re p ro d u c tio n could be made fro m "photographs" if e s s e n tia l to th e u n d is ta n d in g of th e dissertation. Silver prints o f " p h o to g ra p h s " may be ordered a t additional charge by writing the O r d e r D epartm ent, giving th e catalog number, title , author and specific p a g e s you w ish reproduced. University Microfilms 3 0 0 North Zeeb R o a d A n n Arbor, M ic h ig a n 48106 A X e r o x Education Company 73-5351 CONNOR, Lawrence John, 1945CCMPONENTS OF STRAWBERRY POLLINATION IN MICHIGAN. Michigan State University, Ph.D., 1972 Entomology University Microfilms, A XEROX Company, Ann A rbor, Michigan COMPONENTS OF STRAWBERRY POLLINATION IN MICHIGAN By Lawrence John Connor A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Entomology 1972 P L E A S E N OT E: S o m e p ag es m a y hav e ind i s t i n c t print. F i l m e d as receive d. University Microfilms, A Xerox Education Company ABSTRACT COMPONENTS OF STRAWBERRY POLLINATION IN MICHIGAN By Lawrence John Connor A system of evaluating the effectiveness of strawberry pollina­ tion in commercial fields is presented based upon flower and insect related pollination mechanisms. Strawberry flowers were pollinated through self-, wind-motion, and insect pollination mechanisms, although the relative amount each contributed to the pollination of a specific cultivar was related to floral morphological aspects— particularly stamen and receptacle height of that cultivar. Based upon observa­ tions on 11 cultivars., self-pollination resulted in 53% achene set, the addition of wind-motion resulted in an average of 67% achene set, and the addition of insect pollinators resulted in 91% achene set. Insect pollination contributed greatest to the pollination of inter­ mediate and short-stamened flowers with tall receptacles, while selfpollination and wind-motion pollination made the greatest contribution to flowers with stamens taller than the receptacle. Stamen height was correlated at the 1% probability level with percent achene set in cloth covered cages (r = 0.657, n = 44) and in screen covered cages (r = 0.599, n = 44) although considerable variation was present in these data. Further correlation of stamen height of the primary, Lawrence John Connor secondary, tertiary and quaternary flowers with the corresponding percent achene set demonstrated significance at the 5% probability level only in the primary and secondary berries in the self pollinated plots, and only the primary berries in the wind-motion pollinated plots. This variation was due to other morphological aspects of the flowers, par­ ticularly differences in the ratio of the height of the stamens to the height of the receptacle. Within a cultivar, as stamen height increased from primary to quaternary flowers, the height of the receptacle on the corresponding flowers decreased, causing the variations in the data. Insect pollinators approximately the size of honey bees (Apis mellifera L.) touched both the stamens and stigmas of hermaphroditic flowers during their visits, while smaller insects usually remained outside the ring of stamens. berry fields in 1970 was: and Megachilidae 1%. The relative prevalence of bees in straw­ Apidae 35%, Andrenidae 14%, Halictidae 52%, The distribution in 1971 was: Apidae 31%, Andrenidae 20%, and Halictidae 49%. Maximum bee activity on strawberry flowers was observed between 10 a.m. and 3 p.m., at average temperatures ranging from 65 to 79°F., and at low wind speeds. 'Midway 2' and 'Midway 1' attracted the greatest number of bees and flies while 'Sunrise' and 'Redchief' were less attractive. Both 'Midway 1' and 'Midway 2' were good pollen pro­ ducers, based upon pollen collection by honey bees, while 'Sunrise' and 'Redchief' were poorer. Plants competing with strawberry flowers for honey bee pollen collection were: choke cherry (Prunus spp.), apple (Pyrus malus), dandelion (Taraxacum officinale), mustard (Brassica sp.), yellow rocket (Barbarea vulgaris), and willow (Salix spp.). When Lawrence John Connor overall pollinator populations were low in large fields, the pollinators aggregated along the edges of the field. Strong wind exposure in open fields during bloom decreased bee populations, limiting foraging to areas protected from wind. Fields surrounded by cultivated soil and orchards had fewer native bees than fields surrounded by uncultivated land; likewise, honey bees were present in greatest numbers in those fields where colonies were present within or adjacent to the strawberry field. Finally, insecticide use during flowering seriously reduced numbers of insect pollinators, which consequently reduced the level of achene set. The author recommends that horticulturalists developing new strawberry cultivars work with entomologists to evaluate the pollina­ tion needs of each new release, providing each new cultivar with fair evaluation under optimum pollination conditions. TABLE OF CONTENTS Page LIST OF T A B L E S .................................................. iv LIST OF F I G U R E S ................................................. v INTRODUCTION ..................................................... 1 LITERATURE ....................................................... Floral Hierarchy .............................................. Floral Morphology .......................................... Pollination Mechanisms ........................................ Insect Pollination Studies .................................... Insect Activity on Strawberry Flowers ........................ Environmental Influences ...................................... Cultivar Preferences by Bees and Flies ........................ Pesticide Influence on StrawberryPollination ................. METHODS AND MATERIALS .......................................... Cage S t u d i e s ................................................... Stamen Height Comparisons .................................... Greenhouse Study ............................................... Insect Pollinator Studies .................................... R E S U L T S ........ . ................................ Cage S t u d i e s .......... • Stamen Height Comparisons ............ . . . . . . . Greenhouse Study ............................................... Insect Pollinators of Strawberries ............................ 3 4 5 5 7 8 8 9 9 12 12 13 16 16 19 24 28 DISCUSSION....................................................... 45 LITERATURE CITED ................................................. 55 APPENDICES....................................................... 73 I. Cultivars, Field Locations, and Dates of Cage Placement and Removal for1971 Cage S t u d y ............. ii 73 Page APPENDICES (Cont'd) II. III. Results, 1971 Cage S t u d y ................................. Source and Description of 10 Cultivars Used in 1971 Greenhouse Evaluations... ...................... IV. 1969 - 1971 Sweep Net CollectionP a r a m e t e r s .............. iii 74 76 77 LIST OF TABLES Table 1. 2. 3. References Comparing Yields with and without Insect Pollination ...................................... 6 Yields from 1969 and 1970 Cage Studies on Midway 2 Plants. Plots Located in Kaleva, Michigan in 1969 and in Hartford, Michigan in 1970 .......... 17 Contribution of Self-, Wind-motion and Insect Pollination to Strawberry Set and Achene Set in 11 Cultivars from 6 Michigan Fields. 1971 . . . 18 4. Average Stamen Height of Cultivars Used in 1971 Cage Study. 10 Flower Measurements/subsample, 40 Total/sample. In mm .......................... 20 5. Correlation Coefficients for Self- and Wind-motion Pollinated Plots of 11 Cultivars and the Corresponding Levels of Achene Set .............. 25 6. 7. 8. 9. 10. 11. Weight/berry and Percent Achene Development with and without Honey Bees in Separate Greenhouse Rooms— 1971 Greenhouse Study ............................ 26 Period of Blooming of Individual Flowers of 9 Cultivars Growing in the Greenhouse with and without Honey Bees. January and February, 1971 . . 27 Breakdown, by Percentage, of Bees Collected in Commercial Strawberry Fields in 4 Michigan Counties in 1970 and 1971, with Summaries by County . . . . 29 Identity and Efficiency of Strawberry Flower Pollinators ...................................... 31 Concentration of Bees Along Edges of Commercial Strawberry Fields and Low Bee Density, and the Resulting Percent Achene Set .................... 39 Plant Source of Pollen Pellets Returned to Colonies of Honey Bees Located in 2 Commercial Strawberry Fields Consisting of Different Cultivars ........ 42 iv LIST OF FIGURES Figure 1. 2. 3. 4. 5. 6. 7. Page Correlation of Percent Achene Set in Self Pollinated Plots with Average Stamen Height in each of Primary, Secondary, Tertiary, and Quaternary Flowers ..................................... 22 Correlation of Percent Achene Set in Wind-motion Pollinated Plots with Average Stamen Height in each of Primary, Secondary, Tertiary, and Quaternary Flowers ..................................... 23 Relationship Between Number of Honey Bees per 100 Sweeps in Different Commercial Strawberry Fields and the Percent Achene Set (Arcsin Transformed % Values). Curve Hand-fitted ............................ 33 Relationship Between the Percent Achene Set Due to Insect Pollination in the 1971 Cage Study (Calculated as Difference Between Open Plots and Screen Cages) and Pollinator Density in the Different Fields (Arcsin Transformed % Values). Curve Hand-fitted...................................... 34 Influence of Time of Day on Honey Bee and Native Bee Density in Commercial Strawberry Fields as Determined by Repeated Sweep Net Collections in 4 Michigan Counties in 1970 and 1 9 7 1 .................. 35 Influence of Temperature (°F) on Honey Bee and Native Bee Density in Commercial Strawberry Fields as Determined by Repeated Sweep Net Collections in 4 Michigan Counties in 1970 and 1 9 7 1 ................................................... 37 Influence of Wind Speed (mph) on Honey Bee andNative Bee Density in Commercial Strawberry Fields as Determined by Repeated Sweep Net Collections in 4 Michigan Counties in 1970 and 1 9 7 1 .................... 38 Figure 8. 9. 10. 11. 12. 13. 14. Page Cultivar Attractiveness to Insects of Four Cultivars Grown in Michigan, Band upon Sweep Net Collections (A) and Row Counts (B and C). Numbers at Left of each Bar Represent the Number of Sweep Collections (A) or Rows (B and C) Included in the Mean V a l u e ............................ 41 Native Bee Density in Commercial Strawberry Fields as Influenced by the Percent of Surrounding Land in Agricultural U s e .................................... 44 A Conceptual Picture of the Strawberry Pollination System Observed in MichiganStrawberry Fields ........... 46 Flow-chart Designed to Allow Growers, Beekeepers, Horticulturalists and Entomologists to Evaluate the Level of Pollination in Specific Fields. Remedial Procedures are thenSuggested ................. 53 Various Aspects of Floral Morphology of Strawberry Flowers. A— 'Redchief', with Tall Receptacle and Shorter Stamens; B— 'Guardian', also with Stamens Shorter than Receptacle; C— Honey Bee on Flowers with Stamens Approximately Equal in Length to Stamen Height; D— 'Midway 1 ’ Flowers with Stamens Taller than Receptacle; E— Honey Bee on Flower with Stamens Equal in Length to Stamen Height; and F— Flower at the End of Anthesis, Loosing Petals, with Pollinated Pistils Darkening ...................................... 59 Various Degrees of Pollination. A— Only 2 or 3 Pollinated and Enlarged Achenes; B— About 10 Enlarged Achenes Producing Nubbin or Button Shape, Note Small Size of Unfertilized Ovules. C— Random Achene Enlargement from Self-pollination; D— Nearly Complete Pollination, with Only a Few Unpollinated Ovules in Creases and at Berry Tip; E— Pistillate 'NJ 264', Hand Pollinated after Petals had Fallen, Showing Pistil Receptivity only at Tip of Receptacle (Berry); F— 'Guardian' Berries Resulting from Self-Pollination, with Characteristic Nubbin or Button Appearance ............................ 61 Honey Bee Activity on Strawberry Flowers. A, B, and C— Shows a Single Bee Visit to a Flower with Bee Following a Clockwise Direction. The Bee is Centered Over the Top of the Receptacle During Much of the Visit. D and E— Honey Bee Touching Pistil and Stamens During Same Visit. F— Honey Bee on Pistillate Flower, Seeking Nectar ......................................... 63 vi Page Figure 15. 16. 17. 18. Several Native Bees on Strawberry Flowers. A and B— Andrenine on Top of Receptacle. C and D— Halictines Working Anthers from Outside of 'Wall' of Stamens, Eliminating Most Contact with Pistils and Thus Minimizing Pollination ........................ 65 Typical Flower Stems from Open Pollinated Plots, Screen Covered Plots, and Cloth Covered Plots, Representing Insect, Self and Wind-motion Pollination Respectively. A, B, C— 'Sunrise': Open Screen, Cloth Cages, Respectively; D, E, F— 'Midway 2' Open, Screen, ClothRespectively ............. 67 Similar to Figure 16, with 'Redchief' A, B, C— Open Pollination, Screen Cages, and Cloth Cages Respectively; D, E, F— Open Pollination, Screen Cages, and Cloth Cages for 'Guardian', Respectively .......................................... 69 Short Stamened 'Surecrop' Yield in Open Pollination Plots (A) and Screen Covered Plots (B) Compared to Cloth Covered Cage of Tall Stamened 'Midway 1' (C). In D, E, F, Primary Berries of 'Redchief' that were Harvested at 0, 75 and 150 Feet from the Edge of a Field with Low Pollinator Density, Showing Poorer Berry Quality in the Center of the Field. There was a 20% Decrease in the Level of Achene Set from the Edge of the Center of this Field. . . . . . . . 71 vii INTRODUCTION Continual study and review of the pollination mechanisms and requirements of agricultural crops are needed to keep abreast with new cultivars, changing economics of production, and new cultivation and harvest techniques. In Michigan, such studies have been conducted on blueberry pollination (Dorr and Martin, 1966; Brewer, Dobson, and Nelson, 1969a, 1969b; and Brewer and Dobson, 1969a, 1969b), and on cucumber pollination (Connor and Martin, 1970, 1971; and Collison and Martin, 1970). Because commercial strawberries grown in Michigan lacked such a review, the author surveyed the status of strawberry pollination to isolate the major components of pollination of straw­ berries. By isolating these mechanisms it was possible to develop a system to evaluate strawberry pollination in commercial fields. Varia­ tions in this system were investigated to provide better understanding of strawberry pollination mechanisms. 1 LITERATURE Most commercial strawberry flowers are self-pollinated, and to understand the mechanisms of strawberry pollination, we must first understand the morphology of the flower. Modern strawberry cultivars are the result of man's selection from the genetic material of 3 species of wild strawberries, Fragaria spp. Two of these species were transported to Europe in the American colonial period. There is cir­ cumstantial evidence that they were grown together in gardens and chance seedlings resulted from their accidental hybridization. The hybrids were the progenitors of a new type of strawberry with large berries. These two species were Fragaria virginiana L., of Eastern North America, and F. chiloensis, native to the Pacific coast of North and South America. Fragaria ovalis was also incorporated into some cultivars (Darrow, 1966). The first cultivars were generally dioecious, possessing sepa­ rate staminate and pistillate plants. Hermaphroditic selections were not productive in the early days of the industry, and only set a small percentage of the flowers on each inflorescence. However, through plant breeding, hermaphroditic cultivars have been obtained which give nearly 100% berry set (Darrow, 1966). 2 3 Floral Hierarchy There is a predictable hierarchy on flower stems which dictates the order of flowering, the number of pistils per flower, and the relative size of the berry. Typically there are one primary, two secondary, 4 tertiary, and 8 quaternary berries per inflorescence (Darrow, 1966). Because this pattern varies either with multiple or with incomplete branching on the stem, varying numbers of flowers are possible on a inflorescence (Janick and Eggert, 1968). The primary flower of an inflorescence is the largest, has the most pistils, and opens first. order. Secondary flowers are somewhat smaller, and open next in Later, the still smaller tertiary and quaternary flowers follow. Floral Morphology Strawberry flowers are typically 5-merous with white petals sub­ tending 20 to 35 stamens in 3 whorls. length within the same flower. The stamens differ in size and Anthers are a deep golden yellow when they contain pollen, but turn pale as pollen is released. Undeveloped stamens, called staminodia, occasionally appear on the same flower with good stamens, while other flowers have only staminodia (Darrow, 1966). Inside the circle of stamens is a cone-shaped structure called the receptacle. This is an extension of the stem and is covered with a few to over 500 pistils arranged in a spiral pattern. long and narrow with rough sticky stigmas. is an ovary containing an ovule. Pistils are At the base of the pistil The true fruit is an achene; the aggregate of achenes on the fleshy receptacle forms the commercial berry. Fertilization occurs in 24 to 48 hours following pollination; 4 the seeds are mature before the berries reach full size and become red (Darrow, 1966). There is a direct relationship between the number of developed achenes and berry weight (Gardner, 1923; Robbins, 1932; and Nitsch, 1950, 1952). Fertilization of ovules releases growth substances which stimulate receptacle growth: unfertilized ovules remain small and are surrounded by undeveloped flesh. When a large number of achenes are unfertilized, a noticeable shrunken 'knot' or depression appears and the berry is poorly shaped. Pollination Mechanisms Strawberry pollen matures prior to anthesis and is released when the anthers open along lateral slits. Sometimes the heavy, sticky pollen is under tension and is thrown out on the adjacent pistils and petals (Knuth, 1906). 1927). Later it dries and may become airborne (Darrow, However, strawberry flowers are not considered wind-pollinated within the accepted definition because their pollen does not travel far into the air. The stigmas are small and pollen production is limited when compared to true wind-pollinated species. However, a minimal amount of wind pollination may occur in hermaphroditic flowers (Faegri and van der Pijl, 1966). Strawberry flowers benefit from the closeness of the anthers to adjacent pistils. Thus, some self-pollination is possible in hermaphroditic cultivars, but seldom provides for complete pollination of all pistils on a flower. For example, Swarbrick and Thompson (1933) obtained more complete pollination when pollen was brushed over the entire receptacle of the flower than when the flowers 5 were undisturbed. And Allen and Gaede (1963), using greenhouse plants, reported 20% normal berries from undisturbed flowers, 77% normal berries from wind-pollinated flowers, and 97% from brush pollinated flowers. Finally, Way (1968) noted that berries grown in a greenhouse without wind were more misshapen than berries grown in the open. Insect Pollination Studies Insect pollinators were essential for the pollination of early types of strawberries and necessary in the pollination of pistillate cultivars popular several decades ago (Darrow, 1966). Fletcher (1917) considered insects responsible for over 90% of all strawberry pollina­ tion. Recently, many studies have been conducted with insect pollinators, all indicating that insects increase yield: either increased berry set, increased berry weight, increased achene set, or decreased nubbins (Table 1). Insect Activity on Strawberry Flowers Nearly all previous reports of insect activity on strawberry flowers dealt with observations on the honey bee, Apis mellifera L. They visit strawberry flowers to collect pollen and/or nectar. Nectar collectors touch both pistils and stamens on nearly every visit: they often landed on the side of the flower and walk over the stigmas; pollen collectors often stood on the pistil-covered receptacle and pivoted on the flower or circled around the stamens scrabbling for pollen (Free, 1968b). Honey bees vary in the length of time spent on individual flowers ie., 7 seconds (Petkov, 1965), 7.6 to 10.6 seconds (Free, 1968b). Free (1968b) noted that honey bees worked 12 to 14% of TABLE 1.— References comparing yields with and without insect pollination. REFERENCE OBSERVATIONS Strebtsova (1957) Found by regulating the number of honey bee visits to flowers that berrysetin­ creased up to 11 to 16 visits, whilethe quality and weight of individual berries increased up to 60 visits. Hughes (1961) Extremely misshapened berries of unmarket­ able quality in screen cages with no bees. Petkov (1965) Flowers isolated in screen cages set 31 39% vs. 55 to 60% in open plots.In screen cages berry deformity was equal to 60 to 65%, vs. 14 - 18% in uncovered plots. Rajput and Singh (1967b) Insect pollinator exclusion reduced fruit set 8 to 18% in 1962 and 2 to 8% in 1963. Moore (1969) Pollinator exclusion increased the per­ cent of poorly formed berries, anti de­ layed ripening of 2 out of 3 cultivars. Mommers (1961) Improved berry weight and berry quality when insect pollinators were present. Free (1968a) Greater berry set, larger, better shaped berries. Free (1968b) Yields without bees in cages resulted in lower berry set, lower average berry weight and lower percentage of well formed berries. Couston (1966) Open plots gave a higher proportion of marketable fruits than in cage plots. 7 the exposed flowers as they visited. Pollen collection by honey bees peaked from 11 a.m. to 2 p.m. (Free, 1968b) and ranged from 39% (Free, 1968b) to 48 to 78% (Petkov, 1965) pollen collection by honey bees. Mitchell (1960) cited numerous bee species as visitors to Fragaria, particularly from the families Andrenidae and Halictidae. However, the role of these insects as pollinators was unknown in Michigan. Also, the hover flies, Eristalis and Syrphus, were noted by the Horticultural Educational Association, (1961). Free (1968b) re­ ported that Bombus spp. rarely visited strawberry flowers. Environmental Influences Cool temperatures influence both insect visits to strawberry flowers and flower development. Kronenberg et al (1959) found that cultivars differed in their responses to temperature:ie., they found that 'Deutsch Evern' produced berries at temperatures lower than 'Jacunda'. Greater exposure to wind increased the number of poorly shaped berries or nubbins when compared to well protected fields (Kronenberg, et al 1959). Although cool temperatures prolonged the period of receptivity of pistils (Moore, 1964) more malformed berries were produced in wet and cool weather. Furthermore, cold temperatures reduced pollen formation, fertility, germination and receptacle develop­ ment, as well as the ratio of number of achenes to berry weight (Thompson, 1971). Heavy rainfall reduced achene development and in­ creased the frequency of malformed berries: repeated drops of water in newly opened flowers prevented berry set or produced very abnormal berries (Marshall, 1954). 8 Cultivar Preferences by Bees and Flies Strawberry cultivars are extremely variable in their pollen production (Darrow, 1966), and honey bees collect much more pollen from some cultivars than others (Free, 1970). Skrebtsova (1957) found that bees visited the cultivar 'Misouka' more frequently than either 'Krasavitsa sagoria' or 'Komsomolka' at rates of 578, 429, and 328 visits respectively. Skrebtsova found that 'Misouka' had larger anthers, produced more pollen, and secreted more nectar than 'Krasavitsa sagoria'. Pesticide Influence on Strawberry Pollination Pesticides applied to strawberries in bloom may reduce or eliminate native bee and honey bee pollinators from those fields. Some pesticides also cause additional harm because of their phyto­ toxicity to strawberry pollen (Eaton and Chen, 1969; Bennet, 1968; Lockart, 1967). The Michigan Fruit Spraying Calendar (Thompson et al, 1972) recommends insecticide use at or before 10% king (primary) bloom to control plant bug and fungicide applications several times during bloom. By following this program, growers may deleteriously affect both insect pollination and pollen fertility (Eaton and Chen, 1969). METHODS AND MATERIALS Cage Studies Different style cages were used in 1969, 1970 and 1971 to isolate the components of strawberry pollination, to measure the rela­ tive contribution of each component to the overall pollination of the flower, and to seek differences in the pollination requirements of different cultivars. The 1969 plots were located at the Fruit Haven farm in Kaleva, Michigan where 16 plots of Midway 2 plants were divided into 4 treatments: 1. Brass window screen cages (4) measuring 2 x 4 x 1.5 ft were placed over plots and covered with clear plastic to restrict wind movement through the cages, thus measuring the level of self-pollination; 2. Brass window screen cages (4) of the above dimensions were placed over plots and used to measure any increase in yield resulting from wind-motion pollination; 3. Brass window screen cages (4) of the same dimensions were placed over plots supplied with queenless, one-pound nuclei of honey bees in cardboard containers. Weather conditions were poor and the nuclei remained alive for 7 days. 4. Open pollinated checks (4), without any covering, were used to measure the production of berries in a commercial field where native bee and fly pollinators were present. Although slits were cut into the plastic sheeting to allow air flow, temperatures increased in the cages and caused condensation and leaf enlargement. There were no visible changes in the flowers or the flower 9 10 stems, except that petal-fall was slow because of incomplete pollina­ tion and absence of wind. Ripe berries were harvested on June 26 and July 2 and berries weighed in grams and graded according to the percent of malformed berries. In 1970, 8 x 12 x 6 ft cages allowed the use of larger nuclei of honey bees in 2 of the 5 treatments and to give the bees better flight conditions. A commercial field of Midway 2 plants in Hartford, Michigan was used, with each of the 5 treatments replicated twice. The treatments were: 1. Plastic-covered screen cages. Four-mil thick plastic sheeting covered screen cages and these were used to measure yields resulting from self-pollination; 2. Screen cages, used to measure the changes in yield resulting from wind-motion pollination; 3. Plastic-covered screen cages containing honey bees, used to measure the increase in production from honey bees but with­ out help from wind-motion pollination; 4. Screen cages containing honey bees, used to measure the change in yields due to honey bees and wind motion pollina­ tion; 5. Open pollination checks, used to compare cage yields. One small 6-frame colony was placed near the cages to supple­ ment the moderate native bee population present in the field. Colonies in the cages were provided water and fed pollen cakes. The plastic covering on the corresponding cages was slit at the top to allow heat to escape, although again some tempterature buildup was noted. However, the temperature did not seriously change bee behavior or plant growth. Each plot was harvested twice, the average weight per berry determined, and the percent achene set rated for individual berries. The percent achene set was much more precise in determining 11 the level of pollination than the percent malformed berries, as done in 1969. In 1971, 11 cultivars were tested for self-, wind-motion, and open pollination using smaller cages than in 1970. Because of heat buildup experienced in 1969 and 1970, white muslin cloth was sewn into cages for one set of treatments to restrict both wind and insect activity, but to allow air flow. Cages measured 18 x 48 x 15 in and were used in 2 of the 3 treatments: 1. Cloth-covered plots were used to check the level of self pollination; 2. Screen covered plots were used to determine the amount of pollination resulting from both self pollination and windmotion pollination through the screen; 3. Open pollinated plots were used to measure the combined level of self, wind-motion, and insect pollination. By estimating the percent achene set to the nearest 10% on the primary, 2 secondary, 2 tertiary and 2 quaternary flowers per inflorescence, berries on 25 flower stems were evaluated for extent of pollination from each plot. In addition, the percent berry set was calculated for each plot. Each year, cage differences were tested with the analysis of variance, and when differences were found at the 5% probability level, the Student-Newman-Keul multiple comparison test (Sokal and Rohlf, 1969) was used to separate means. The estimated percent achene set was transformed prior to statistical analysis by using the arcsin function; data in the Results section appear as untransformed percentages, data in Appendix II contain both transformed and untransformed data. 12 Stamen Height Comparisons In conjunction with the 1971 cage study, the length of stamens were measured in mm, in primary, secondary, tertiary and quaternary flowers for each cultivar tested, using the longest stamens in each flower (noticeable within-flower variation was evident). The mean values for each cultivar were correlated with the percent achene set obtained in the cloth-covered and screen covered cages, in an effort to determine the importance stamen height had on the pollination of straw­ berry flowers. These data were also separated by primary, secondary, tertiary and quaternary flowers for purposes of analysis. Greenhouse Study Ten cultivars were started in the greenhouse in January, 1971 and grown in the same room until the appearance of the first flowers. Then 35 plants were arranged in each of two rooms for each cultivar tested. A randomized block arrangement with 7 groups of 5 plants each were grouped to equalize microclimate differences in the rooms. Plants were watered directly into the pot to avoid disturbing the flowers. Automatic equipment maintained temperature at a 75°F minimum, and a 16 hour photoperiod. When berries were ripe they were individually harvested, weighed and the percent achene set determined. Tn the room without bees achene set was determined by counting the actual number of enlarged achenes and dividing by 200, an arbitrary estimate, while in the room with bees, the increased numbers of achenes necessitated the estimation of percent achene set to the nearest 10%. To determine the effect of insect pollination on the length of time of individual flower bloom, the time of flowering was recorded in 13 both rooms. The corresponding time intervals were compared with analysis of variance. Flowers were also observed for changes in overall appearance during flowering. Insect Pollinator Studies The density of insect pollinators in different commercial strawberry fields was estimated by using a standard 15 inch insect sweep net. From 200 to 500 sweeps, the number depending upon field dimensions, were made over single rows of commercially growing plants. Cultural, climatic and spray information were recorded at the time of sampling. At an early stage, when mostly primary and secondary berries were ripe, rows adjacent to those swept were sampled to provide an estimate of the level of pollination present in that field. A rating system used by Kronenberg et al (1959) was modified and the percent achene set estimated to the nearest 5% or 10%. Samples consisted of from 5 to 25 flower stems and their berries; they were rated immediately or frozen until rated. On each stem, the primary, 2 secondary, 2 tertiary, and 2 quaternary berries were rated, or 7 berries representing the serial progression in blooming were used. The percentage berry set was recorded by counting the number of flowers and the number of developed berries. Data were analyzed using analysis of variance and the Student-Newman-Keul multiple comparison test. Correlations were attempted between pollinator density and the level of achene set found in different fields; similar comparisons were made between pollinator density and the level of achene set due to insect pollinators found in the 1971 cage study discussed earlier. In both cases, the percent achene set values were transformed by the arcsin function. 14 In 1970 and 1971 insect pollinators were collected in 4 Michigan counties using a sweep net. Immediately after collection, the insects in the samples were killed in cyanide jars and honey bees sorted by the presence or absence of pollen pellets on their corbiculae. Al­ though nectar collecting bees collected pollen incidently, if a bee had a pollen pellet of any size, it was classified as a pollen collector. Other bee and fly species were preserved and used for comparing pol­ linator populations in different areas of Michigan. Observations were made on the behavior of different insects as they worked strawberry flowers, and some of their activities recorded on Super-8 movie film. From these observations the author identified different groups based upon pollinator efficiency. Relative pollinator densities were compared for different times of day, temperature, wind speed and location by using the sweep net collections. Over 200 samples were made under various conditions to make the above comparisons and to compare aspects of wind protection, pesticide applications, and cultivar attractiveness. comparisons, only similar conditions were used: In making such for example, compari­ sons of cultivar attractiveness were only made under favorable flight conditions, and all cultivars were examined under the same factors. Sweep net collections were replicated within fields whenever possible. Insect pollinators were visually counted on equal length rows (approximately 250 feet) to verify observations concerning cultivar attractiveness. A large field on the Fruit Haven Farm, Kaleva, Michigan, was particularly suitable in that it had several cultivars growing under nearly identical conditions in several sections of the field. 15 Pollen traps, of the style used by Kremer (1949), were placed in front of strong colonies of honey bees in 2 commercial fields to compare the relative attractiveness of strawberry pollen from 2 cultivar groups. One field consisted of entirely 'Redchief', while the second consisted of 75% 'Midway 1' and 'Midway 2', and 25% 'Sunrise', 'Surecrop', 'Redchief' and several miscellaneous cultivars present in small amounts. The resulting pollen pellet samples were identified to plant species by Larry G. Olsen^ providing information regarding pollen collection by honey bees from the two fields. In addition, useful information was gathered concerning the plants which compete with strawberry flowers for honey bee visits. Finally, land surrounding each commercial field was assessed as either cultivated, orchard, woodlot, unused, etc., with concern for possible sites for ground-nesting native bees. Observations were also made to see if honey bee colonies were located near the field. The resulting bee density was then compared with these observations. ^Graduate assistant, Department of Entomology, Michigan State University. RESULTS Cage Studies In 1969 and 1970 average berry weights were similar for the dif­ ferent treatments, and estimates of berry quality followed the same trend (Table 2). Plastic covered cages, which eliminated both wind motion and insect activity from strawberry flowers, produced the lowest yields, followed by the screen covered plots which allowed wind motion but no insect pollination. Both the plastic and screen covered plots without bees produced berries of approximately the same weight, while there was slightly better shape and percent achene set in berries from the wind-motion pollinated plots. The addition of honey bees into plastic or screen cages improved yield considerably, closely approaching or equalling the yields found in uncovered, open pollinated plots. While open pollinated checks out-yielded plots caged with bees in 1969, they failed to do so in 1970. This may have been because the bee nuclei died within 7 days in 1969, and survived in 1970. Two significant facts were observed in the 1971 cage trials: first the level of achene set for all 11 cultivars increased from clothcovered cages (53%) to screen covered cages (67%) to open pollinated plots (91%) (Table 3), indicating that wind motion improved percent achene set over self-pollinated flowers, while open pollinated plots out-yielded either self- or wind-motion pollination. 16 Secondly, there 17 t TABLE 2.— Yields from 1969 and 1970 cage studies on Midway 2 plants. Plots located in Kaleva, Michigan in 1969 and in Hartford, Michigan in 1970. 1970 1969 CAGE DESIGN No. berries Weight/ Percent berry malformed No. berries Weight/ berry Percent achene set PLASTIC COVERED SCREEN 388 4.6a 92%a 755 5.5a 51% SCREEN 351 7. Oab 33b 310 5.8a 62 PLASTIC + BEES 617 0 7.2b 68 SCREEN + BEES 397 7.5b 20c 294 7.7b 71 OPEN CHECK 485 9.1c 9d 447 7.3b 80 Means in each column followed by the same small letter are not significantly different at the 5% probability level (Student-Newman Keul multiple comparison test). 18 TABLE 3.— Contribution of self-, wind-motion and insect pollination to strawberry set and achene set in 11 cultivars from 6 Michigan fields. 1971. Percent Berry Set Percent Achene Set Cultivar Cloth Cage Screen Cage Guardian 47% 93% Surecrop 96 99 Earlidawn 90 Sunrise Open Plot 95% Cloth Cage Open Plot Screen Cage 80a 35a 53 b 100 48 b 61 100 99 48 b 46a 87 97 100 49 be 65 M 828 95 99 99 49 be 90 Redchief 91 97 99 51 be 61 Midway 2 80 93 99 53 be 70 M 788 84 92 99 54 be 73 M 772 43 66 93 61 c 64 M 766 88 96 97 62 c 56 be Midway 1 93 96 100 78 Mean 81 93 98 53 d 97 67 98 cd 76a 75 cd 96 d 95 cd ef 91 c f 95 cd de g cd d 99 88 b h 100 91 Percentages in each of the 3 percent achene set columns denote no statistical difference at the 5% probability level when followed by the same small letter. 19 were significant differences between results of self and wind motion pollination, attributable to the differences in the 11 cultivars. For example, cloth covered plots of Guardian produced 35% achene set, while Midway 1 produced 78%; similarly in screen covered plots, Earlidawn produced 46% achene set, compared to 97% in Midway 1. Differences were also found in the open pollinated plots, but these were largely due to differences in pollinator densities present in the different fields. Differences in the percent berry set also increased from cloth-covered (81%), to screen covered plots (93%) to open pollinated plots (98%), but the variation was not as large as those for percent achene set (Table 3). Stamen Height Comparisons The average stamen height for the 11 cultivars varied from 2.4 to 5.2 mm, although 9 of the 11 cultivars ranged from 3.0 to 4.0 mm (Table 4). There was a great deal of variation within each cultivar; for example, cultivar ’Guardian' had 1.9 mm stamens in primary flowers, but 4.6 mm stamens in quaternary flowers. Three cultivars were examined in more than one field, but none showed any statistical differences due to field location. Thus there was one 'short' stamened cultivar, 9 'intermediate' stamened cultivars, and one 'long' stamened cultivar. Correlations of stamen height and percent achene set were statistically significant at the 5% level for both self-pollinated flowers (r = 0.657, n = 44) (Figure 1), and for wind-motion pollinated flowers (r = 0.599, n = 44) (Figure 2). By dropping the values from the 'short' and the 'long' stamened cultivars, thereby testing only the intermediate length TABLE 4.— Average stamen height of cultivars used in 1971 cage study. sample, 40 total/sample. In mm. GROWER CULTIVAR Culby Piggott Hassel AVERAGE Sunrise Sunrise Sunrise Sunrise SUNRISE Culby Piggott Radewald Lutz AVERAGE Midway Midway Midway Midway MIDWAY 10 flower measurements/sub­ PRIMARY SECONDARY TERTIARY QUARTENARY 2.5 3.2 3.4 3.2 3.2 3.6 3.2 3.6 4.4 3.7 3.8 3.8 4.0 3.9 3.9 4.0 3.7 3.7 3.7 3.8 3.48 3.48 3.68 3.90 3.63 n. s. 2 2 2 2 2 3.6 2.9 3.8 4.1 3.3 3.9 4.6 4.0 4.1 4.4 4.3 4.1 4.2 3.7 4.6 3.7 4.5 4.1 3.85 3.80 3.93 3.95 3.88 n. s. Radewald Hassel Lutz AVERAGE Redchief Redchief Redchief REDCHIEF 2.5 2.3 3.9 4.2 3.7 3.9 4.1 4.1 3.3 3.8 3.58 3.55 3.35 3.49 n. s . 2.5 3.8 3.6 3.6 3.7 Lutz Piggott Hassel Lutz Surecrop Earlidawn Guardian Midway 1 1.9 2.4 1.9 5.0 1.9 2.9 3.5 5.5 3.2 3.3 4. 6 5.2 2.6 3.6 2.5 5.0 2.40 3.05 3.13 5.18 MSU M788 M828 M772 M766 3.0 2.7 3.8 3.0 3.2 3.8 3.7 4.6 3.9 3.9 3.4 4.0 3.0 3.4 3.7 4.2 3.28 3.45 3.65 3.95 Lutz MSU MSU MSU 2.6 3.2 2.8 AVERAGE SIGNIFICANCE 5% level b b a ab b MEAN OF ALL CULTIVARS 2.97 3.73 3.98 3.94 3.55 Total values followed by the same small letter are not significantly different at the .05 probability level. Each group tested separately. PERCENT ACHENE SET 100 50 1 2 3 4 5 MEAN STAMEN HEIGHT(mm) Figure 1.— Correlation of percent achene set in self pollinated plots with average stamen height in each of primary, secondary, tertiary, and quaternary flowers. PERCENT ACHENE SE MOO > » 50 » * • _* 1 2 3 4 5 6 MEAN STAMEN HEIGHT (mm) Figure 2.— Correlation of percent achene set in wind-motion pollinated plots with average stamen height in each of primary, secondary, tertiary, and quaternary flowers. 24 cultivars, the results of the correlations were still significant at the 5% level, but the 'r1 values were smaller: self pollination r = 0.455, n = 36; wind-motion pollination r = 0.431, n = 36. Correlation of the percent achene set between each of the primary, secondary, tertiary and quaternary flower groups resulted in statistical significance only in the primary and secondary flowers for the self pollinated plots, and only the primary berries in the wind-motion pollination plots (Table 5). Greenhouse Study The results of the greenhouse study may be examined two ways: differences between rooms resulting from the presence or absence of honey bees, and differences between the cultivars located in the same room. Without honey bees, self pollination produced berries averaging 1.0 g in weight and possessing only 5% pollinated achenes, while with honey bee pollination berries averaged 4.5 g in weight and had 69% achene set (Table 6). In the room lacking bees, the differences be­ tween cultivars was considerable: and from 2% to 9% achene set. ranging from 0.2 to 1.8 g in weight The presence of bees did not eliminate differences in weight yields, because of genetically controlled dif­ ferences, but the percent achene set was more uniform, ranging from 55% to 82% achene set. In addition, honey bee pollination decreased the average flowering period from 64 hours to 43 hours (Table 7). one may note that the longer a cultivar had flowers in bloom, the greater the percent achene set which resulted in the self pollinated treatment. Also, TABLE 5.— Correlation coefficients for self- and wind-motion pollinated plots of 11 cultivars and the corresponding levels of achene set. GROUP TESTED NO. DATA POINTS SELF POLLINATED FLOWERS Primary 11 Secondary 11 Tertiary 11 Quaternary 11 ALL FLOWERS 44 ALL FLOWERS EXCEPT MIDWAY 1 & SURECROP 36 MEAN STAMEN HEIGHT "X" MEAN % ACHENE SET 2.96 3.68 3.96 3.61 3.55 3.50 WIND MOTION POLLINATED FLOWERS 11 2.96 Primary Secondary 11 3.68 11 3.96 Tertiary Quaternary 11 3.61 ALL FLOWERS 44 3.55 ALL FLOWERS EXCEPT MIDWAY 1 & SURECROP 36 3.50 r b (slope) a (intercept) STATISTICAL SIGNIFICANCE 46.62 50.07 55.60 59.75 53.01 0.8469 .7783 .2849 .3882 .6572 15.78 12.11 5.25 4.15 10.35 -0.15 5.50 34.83 44.78 16.23 .01 .01 n.s. n.s. .01 55.26 .4554 3.53 -4.45 .01 52.68 63.27 70.99 75.77 65.68 .6760 .5095 .5547 .3660 .5989 16.27 9.97 13.36 5.39 12.89 4.47 26.55 18.16 56.33 19.90 .05 n.s. n.s. n.s. .01 62.79 .4343 11.82 21.42 .01 M y 11 n.s. = no statistical significance at .05 probability level. 26 TABLE 6.— Weight/berry and percent achene development with and without honey bees in separate greenhouse rooms— 1971 greenhouse study. CULTIVAR NJ 267 MEAN WEIGHT PER BERRY In grams --------------------WITHOUT WITH BEES 0.0 n.s. 5.8 e LEVEL OF ACHENE DEVELOPMENT % achene development --------------------------WITHOUT BEES* WITH BEES 0% 587„a 2 a 70 4 82 133-6733 .2 1. 6a GUARDIAN .9 5.8 TIOGA .9 4.2 bed 3 ab 59 ab e b cd i SEQUOIA 1.1 4.7 cde 4 be 55 a 7-6736 1.1 5.2 de 4 be 75 d REDCHIEF 1.3 3.8 bed 6 cd 74 cd SURECROP 1.4 4.5 bede 6 cd 79 d STOPLIGHT 1.5 3.4 b 7 d 76 d MIDWAY 1.8 3.6 be 9 MEAN 1.0 4.5 5 e 66 be 69 *Adjusted values calculated by dividing the actual number of achenes by 200, an 'average' potential number of achenes per berry. **Value in each column followed by the same small letter are not significantly different at the 5% probability level. 27 TABLE 7.— Period of blooming of individual flowers of 9 cultivars growing in the greenhouse with and without honey bees. January and February, 1971. CULTIVAR N flowers ROOM WITHOUT BEES (Hours) N flowers ROOM WITH BEES (Hours) DIFFERENCE and SIGNIFICANCE (Hours) 123 46a 8 28 n.s. 18* TIOGA 10 51a 3 30 21 n.s. 133-6733 96 59a 39 49 10* GUARDIAN 29 62a 8 31 31** SEQUOIA 45 63a 8 57 16 n.s. STOPLIGHT 41 68a 5 44 24* REDCHIEF 16 72a 4 35 37 n.s. SURECROP 63 73a 30 55 18** MIDWAY 23 81 b 18 54 27** 43 21 7-6736 MEAN 64 Means in columns followed by the same small letter are not significantly different at the .05 probability level. Differences indicated are marked * for .05 level and ** for .01 level of significance. 28 After pollination, a conspicous change was evident in strawberry pistils: yellow-green at the start of anthesis, pollinated pistils were a dark brown at petal-fall, giving partially pollinated receptacles a mottled appearance. In their activity, bees stripped the anthers of pollen and often knocked the anthers off the filaments, while self­ pollinated flowers possessed large pollen-laden anthers that persisted throughout berry development. Morphological differences were noted in the appearance of the flowers of different cultivars, particularly in the length of the stamens, the angle of the filament arising from the base of the receptacle, and the size of the anthers. Insect Pollinators of Strawberries Strawberry flowers in commercial fields were visited by a variety of bee species, with the ratio varying significantly from field to field and from the 2 areas of the state the author surveyed (Table 8). Honey bees comprised 32% of the bee population in 1970, and 25% in 1971, with 21% pollen collectors in 1970 and 13% in 1971. The ground nesting bee families of Andrenidae and Halictidae comprised 14% and 52% respectively in 1970, and 20% and 49% in 1971 and were a major part of the pollinating fauna. Ceratina spp. (1% in 1970 and 5% in 1971); Megachilidae (0% in 1970 and 1% in 1971); and Bombus spp. (2% in 1970 and 1% in 1971) were also captured. Manistee and Leelanau counties in Northern Michigan had propor­ tionately more halictines than Berrien and Van Buren counties in Southern Michigan. Ceratina spp. was only present in fields where hollow stemmed plants such as raspberry were available for nesting (Table 8). TABLE 8.— Breakdown, by percentage, of bees collected In commercial strawberry fields In A Michigan counties In 1970 and 1971, with summaries by county. HONEY BEES LOCALITY AND COUNTY Z Z Z Z Z Z Z Z z POLLEN COLLECTORS NECTAR COLLECTORS TOTAL B0MBUS ANDRENIDAE HALICTIDAE CERATINA SPP. MEGACHILIDAE TOTAL NATIVE TOTAL NO. BEES COLLECTED 1970* BERRIEN CO. Benton Harbor Niles VANBUREN CO. Hartford Keeler AVERAGE, SOUTHERN COUNTIES MANISTEE CO. Kaleva Copemish LEELANAU CO. Suttons Bay Lake Leelanau AVERAGE, NORTHERN COUNTIES 1970 AVERAGE 3 1 53 27 56 28 2 3 10 25 32 42 1 1 0 0 44 72 102 110 19 23 17 11 35 35 0 0 24 23 38 36 1 5 2 1 65 65 230 162 14 23 37 1 21 37 2 1 63 607** 18 17 5 3 23 20 1 1 17 18 59 59 0 0 0 0 77 80 732 260 60 29 18 7 78 35 1 0 0 4 20 60 0 0 1 1 22 65 95 539 23 6 29 1 12 57 0 0 71 1626** 2 14 52 1 1 68 2230 21 11 32 1971* BERRIEN CO. Benton Harbor Niles VAN BUREN CO. Keeler AVERAGE SOUTHERN COUNTIES MANISTEE CO. Kaleva - Only Northern Co. 1971 AVERAGE 33 44 12 17 44 61 0 17 5 6 36 11 15 6 0 0 56 39 61 18 18 9 28 0 12 34 26 0 72 65 28 11 39 2 8 32 19 0 61 144** 8 13 21 1 24 54 0 0 79 462** 13 12 25 1 20 49 5 0 75 606 Chi-square comparison of yearly (*) and area (**) results were highly significant (.01 probability level). 30 Honey bees worked strawberry flowers for both pollen and nectar. Pollen gathers 'scrabbled' over the flowers and contacted a large sur­ face area of the stigmas and the stamens, running rapidly in a circular fashion, making 2 or 3 circles per flower. Such pollen gatherers were most often observed during the period of maximum pollen production, occurring from 10 a.m. to 12 p.m. Nectar collectors landed on the top of the flowers and pivoted on the receptacles searching for nectar. Generally, they held one foreleg on a receptacle and the other foreleg on a petal, moving in a circular manner. Honey bees averaged 8.8 flower visits per minute, moving from row to row in a 2 or 5 row limit on a single foraging trip. They visited an average of 11.7 flowers per row. Of the remaining species of bees visiting strawberry flowers, size was the key factor in influencing pollination behavior (Table 9). The families Andrenidae and Halictidae were divided into 2 groups on the basis of size: the first group was approximately the size of a honey bee worker or slightly smaller, while the second group consisted of all smaller bees. Of the andrenines collected, 85% were in the larger group while 15% of the halictines were in the larger class. Larger bees of both families contacted the stigmas and styles of the flower on the same foraging trip, while the smaller bees often remained outside the wall of stamens on intermediate or long stamened flowers and manipulated the anthers for pollen. Short stamened flowers allowed the smaller bees to contact the stigmas and styles on the same visit. Gererally, the small bees were less likely to cross over the top of the receptacle while the larger bees often did. TABLE 9.— Identity* and efficiency of strawberry flower pollinators. INSECT Family Colletldae Collates nudus Robertson NUMBER COLLECTED 3 EFFICIENCY AS POLLINATORS high Family Andrenldae Andrena alleghaniensis Vlereck Andrena crataegl Robertson Andrena perplexa Smith Andrena rugosa Robertson Andrena lata Viereck Andrena mlaerabllis bipunctata Cresson Andrena forbesli Robertson Andrena fragarlana Graenlcher Andrena nasonll Robertson Andrena wllkella Kirby Andrena carllnl Cockerell Andrena vlclna Smith 8 58 3 1 3 71 5 6 137 80 3 68 Intermediate high high Intermediate intermediate intermediate high low Intermediate high high high Family Hallctidae Halictua confusua Smith Hallctus llgatus Say Hallctus rublcundus (Christ) Hallctus parallelua Say Lasloglossum zonolum Smith Lasloglosaum fuselpenne Smith Lasloglossum forbesli Robertson Evylaeus pectoralla Smith Evylaeus dlvergens Lovell Evylaeus foxll Robertson Dlallctus llneatulus Robertson Dlallctus pictus Crawford Dlallctus llllnolensls Robertson Dlallctus perpunctatus Ellis Dlallctus anomalus Robertson Dlallctus tegularls Robertson Dlallctus nymphaerarum Robertson Dlallctus pllosus Smith Dlallctus nymphaaarum Robertson Dlallctus alblpennls Robertson Dlallctus cressonll Robertson Dlallctus retlculatus Robsrtson Dlallctus vlereckl Crawford Dlallctus lnconsplcuus Smith Agapostemon vlrsscens (F) Agapoatenon texanua texanus Cress Agapoatemon splendans (Leri Agapoa tenon radiatus (Say) Augochlorella striata (Provanciier) Augochloropsls metalllca fulglda (Smith) Augochlora pura pura (Say) 786 44 35 2 7 1 43 111 9 29 113 11 23 170 19 14 2 322 131 15 15 5 28 18 1 24 11 9 83 1 3 low Intermediate high hlRh Intermediate intermediate Intermediate low low low low low low low low low low low low low low Intermediate low low high hlRh hlRh high low Intermediate intermediate 38 43 1 intermediate intermediate high Family Xylocopldae Ceratina dupla dupla (Say) Ceratina calcarata Robertson Xylocopa virglnlca virglnlca L Family Apldae Bombus impatlen8 Cresson Bombus blmaculatus Cresson Bombus borealis Kirby Bombus afflnis Cresson Apis mellifera Linnaeus 16 5 5 2 866 hlRh high high high high A Determined by Roland L. Fischer, Department of Entomology, Michigan State University. ♦‘Efficiency determined by amount of contact of both pistils and stamens during foraging. 32 Other insects observed visiting strawberry flowers included: syrphid flies, anthomyiid flies, other flies, plant bugs, lady bird beetles, weevils and other beetles, butterflies and crab spiders. The larger hairy syrphid flies appeared to be helpful in strawberry pollina­ tion; the remaining insects were not considered to be of any importance in moving pollen on the flower from stamens to stigmas. The impact of different bee populations found in various com­ mercial strawberry fields on the resulting achene set shows a significant correlation between honey bee density (Figure 3). In fields of short and intermediate length stamened cultivars, there was a significant relationship (r = 0.537, n = 22), but when data from tall stamened cultivars was included in the analysis, there was no significance (r = 0.219, n = 26). Similar results were found by comparing the density of bee pollinators found in commercial fields where cages were located, and the amount of achene set due to insect pollination in the field (r = 0.587, n = 14) (Figure 4). These data were obtained by subtracting the percent achene set in the screen covered cages from the percent achene set found in the open pollinated plots. Honey bees and native bees were collected in strawberry fields in peak numbers from 10 a.m. to 12 noon, after which they decreased in density until 1 p.m., and then increased in density from 2 to 3 p.m. (Figure 5). In the period from 8 a.m. to 1 p.m., 75% of the honey bees possessed pollen pellets, while from 1 p.m. to 6 p.m. only 52% pos­ sessed pollen pellets. This suggests that the greatest pollen release was in the late morning, which was confirmed by visually examining the flowers. % Achene set (arcsin-degrees) J i 2 s HONEY BEES/100 SWEEPS Figure 3.— Relationship between number of honey bees per 100 sweeps in different commercial strawberry fields and the percent achene set (arcsin transformed % values). Curve hand-fitted. HONEY BEES/IOO SWEEPS Figure 4.— Relationship between the percent achene set due to insect pollination in the 1971 cage study (calculated as difference between open plots and screen cages) and pollinator density in the different fields (arcsin transformed % values). Curve hand-fitted. SWEEPS SWEEPS NATIVE BEES/100 HONEY B EES/100 ©— ©honeybees *— * native bees /\\ / 6 6 s 8a.m. 10 l2noon2pm4 6 8 Figure 5.— Influence of time of day on honey bee and native bee density in commercial straw­ berry fields as determined by repeated sweep net collections in 4 Michigan counties in 1970 and 1971. 36 Bee activity was linked to pollen and nectar availability, as indicated above, but both were influenced by temperature (Figure 6). Strong bee activity was observed first from 65 to 69°F., agreeing with Percival's (1955) observation that the minimum temperature of strawberry anthesis was 62°F. Honey bee and native bee density peaked in the temperature range of 65 to 79°F. Above 80°F, bee activity was reduced, apparently due to a reduction in pollen and nectar supplies. Honey bees were active in strawberry fields at wind speeds up to 19 mph: above this level flight activity was reduced. Native bee activity was highest at low wind speeds with density decreasing pro­ portionately to the amount of wind activity (Figure 7). When bee density was low in commercial fields, the bees remained along the edges of the fields and avoided the center: this fact is supported by the reduced achene set found in the center of fields of short and intermediate length stamened cultivars (Table 10). differences were greatest in the primary flowers. These Cultivar 'Redchief' demonstrated a 20% decrease in achene set between center and edges of the field. Similarly, 'Midway 2' showed a 3 to 12% difference and 'Sunrise' showed a 5% reduction. In 6 other fields with more than 5 bees per 100 sweeps, which represented a high pollinator density, there was no evidence of an edge effect in distribution of bees within the field or achene set. Two commercial fields surveyed in 1971 were protected from strong winds along one border by large trees. The greatest number of insect pollinators was found in the area protected from wind. A field of SWEEPS CO Q . L±J Ll I BEES/100 £ - & UJ > UJ 0-9 10-12 13-1617-19 20-24 25+ Figure 7.— Influence of wind speed (mph) on honey bee and native bee density in commercial strawberry fields as determined by repeated sweep net collections in 4 Michigan counties in 1970 and 1971. co oo TABLE 10.— Concentration of bees along edges of commercial strawberry fields with low bee density, and the resulting percent achene set. FIELD SIZE & CULTIVAR PERCENT ACHENE SET - EDGE PERCENT ACHENE SET - CENTER DIFFERENCE IN YIELD BEES/100 SWEEPS EDGE BEES/100 SWEEPS CENTER 25 Acres Midway 2 1.63 0.86 91.25% 88.50% 30 Acres Redchief 3.30 1.40 84.00 64.50 19.50 8 Acres Midway 2 0.50 0.00 87.50 76.00 11.50 10 Acres Sunrise 1.35 0.80 87.50 82.50 5.00 2.75% 40 'Midway 2' plants had a 4% difference in achene set between the protected and unprotected areas. Concerning cultivar attractiveness to pollinators, 'Midway 2' and 'Midway 1' attracted more insect pollinators than any other cultivar, with greater numbers of pollen collectors appearing in sweep net col­ lections (Figure 8A) and in row counts (Figures 8B and 8C). 'Sunrise' did not attract large numbers of pollen collectors, but did attract a moderate number of nectar collectors. 'Redchiaf' attracted the lowest numbers of nectar and pollen collectors. Pollen traps yielded only 2.4% strawberry pollen from colonies located in 'Redchief' fields, com­ pared to 57% in a large field of predominately 'Midway 1' and 'Midway 2' (Table 11). The following flowering plants competed with strawberry flowers for honey bee activity: choke cherry (Prunus sp.), dandelion (Taraxacum officinale), yellow rocket (Barbarea vulgaris), Brassica sp., sweet cherry (Prunus avium), apple (Pyrus malus), and willow (Salix sp.). The impact of pesticides on bee density in commercial strawberry fields can be determined from sprayed fields. In one field sampled under similar conditions prior to and the day of a Thiodan application, there was a decrease from 1.8 to 0.4 honey bees per 100 sweeps, and 2.3 to 1.5 native bees per 100 sweeps. In a second field there were 0.4 bees per 100 sweeps immediately after a Guthion spray, and 2.9 bees per 100 sweeps 48 hours later. A third field doubled its bee population in 48 hours after a Guthion spray, from 0.5 to 1.0 bees per 100 sweeps. In a fourth field, at 0, 1, 2 and 11 days after a Guthion spray, there were 1.6, 2.1, 3.7 and 3.5 bees per 100 sweeps. Finally, in a fifth CULTIVAR ATTRACTIVENESS TO INSECTS A. SWEEP-NET SAMPLES a ROW-COUNTS Moy 27- 28 Honey bees/100 sweeps * • ••••. ■■ ■fM A.-,' .169 .1 Mttwav2 Honey bees/row 4 * neck#" ;.T 3 ’ 5 Sunrise Midway 1 55 Midway 2 19 17 1 Sunrise 17 Redctsef 10 so so 5 M2 16 4 Ml RE 10 M2 29 Ml RE 20 RE nec. re Ml 16 MMway2 M2 M2 Ml 55 :p^l.; * 13 13 MMwayl • 4V .: T Native bees/row SyrpNdoe/row 23 June 3 4 :: 6 RE Redctief 19 Honeybees/row ;5 - ' M• Sunrise Oiplera/lOO sweeps 10 Ndive bees/row IfcdcWe* Native bees/100 sweeps 23 • M2 Midway I 26 - pq*. • j "ec- C. ROW-COUNTS * Syrphldoe/row 4 4 e 5 M2 4 Ml 6 RE Figure 8.— Cultivar attractiveness to insects of four cultivars grown in Michigan, band upon sweep net collections (A) and row counts (B and C). Numbers at left of each bar represent the number of sweep collections (A) or rows (B and C) included in the mean value. io 42 TABLE 11.— Plant source of pollen pellets returned to colonies of honey bees located in 2 commercial strawberry fields consisting of different cultivars. REDCHIEF PELLET SOURCE MIDWAY 1 AND MIDWAY 2 No. samples with this pollen Percent (mean) No. samples with this pollen Fragaria 2 2.4 19 57.1 Choke cherry 4 71.7 13 25.2 Sweet cherry 0 0.0 7 8.5 Apple 3 5.3 9 21.0 Dandelion 2 7.9 11 13.9 Yellow Rocket 2 6.9 5 13.9 Brassica sp. 1 0.6 9 16.8 Willow 3 18.9 2 1.9 OTHERS 2 0.5 10 1.2 TOTAL NO. SAMPLES 4 19 Percent (mean) 43 field sprayed twice during bloom, pollinator density never exceeded 2.1 bees per 100 sweeps. In addition to pesticide applications, native bee density was greatly influenced by the type of use of surrounding land. Commercial strawberry fields surrounded by non-cultivated soil provided the highest native bee density, while fields surrounded by cultivated land or orchards had very low native bee densities. This variation can be explained by the greater availability of nesting sites for native bees in non-cultivated areas. Cultivated land provided fewer places for bees to build nests (Figure 9). Honey bee density was similarly influenced by the closeness of samples fields to the colony: In 11 fields located within approximately 1/4 mile of colonies of honey bees, there were 1.2 honey bees per 100 sweeps based upon 103 sweep net samples. This is compared to 9 fields lacking honey bee colonies within 1/4 mile from the field: 0.5 honey bees per 100 sweeps based upon 99 samples. there were These data do not include any fields of Redchief which proved to be relatively unattrac­ tive to honey bees irrespective of the closeness of the colonies. 44 c/>E BO 6 4 2 n rt) inn UTILIZED LAND (%) Figure 9.— Native bee density in commercial strawberry fields as influenced by the percent of surrounding land in agricultural use. DISCUSSION Commercially-grown strawberry flowers were pollinated through the interaction of three mechanisms: self-pollination, wind-motion pol­ lination and insect pollination. These mechanisms were controlled by two major components, a 'flower-factor' and an 'insect-factor' (Figure 10). The flower-factor controlled the level of pollination resulting from the flower itself, and included both self-pollination and pollination due to the motion of the wind. It was determined by various morphological aspects of the flower, especially the relation­ ship between the height of the stamen and the receptacle. Different ratios found in different cultivars influenced the percent achene set in various plot treatments. Analysis of the data revealed significant correlations between stamen height and achene set for those berries produced early in the season, but not in later berries. Because stamens were longer on flowers produced later in the season, and the height of the receptacle decreased, the percent achene set increased from the primary to the quaternary flowers. Thus, primary flowers often had tall receptacles with short stamens, while tertiary and quaternary flowers had shorter receptacles and taller stamens. Thus, stamen height relative to receptacle height together determine the achene set more than stamen height alone. 45 46 NEST CLOSENESS COMPETITIVE PLANTS SPECIES EFFICIENCY PESTICIDE USE COMPETITION FLIGHT CONDITIONS I ik POLLINATOR DENSITY i POLLINATOR BEHAVIOR INSECT- FACTOR CULTIVAR ATTRACTIVE­ NESS FLOWER-FACTOR POLLEN PRO- STAMEN RECEPTACLE NECTAR DUCTION,FERTILITY RATIO PRODUCTION 7* SEASONAL t ENVIRONMENTAL \ GENETIC Figure 10.— A conceptual picture of the strawberry pollination system observed in Michigan strawberry fields. 47 Other aspects of floral morphology potentially influence the flower-factor, including the angle of the filaments supporting the anthers, the size of the anthers, and the shape of the receptacle. Cultivars may differ in the amount of pollen they produce, the viability of that pollen and the length of receptivity of the pistils. For example, pistils at the tip of flowers of some cultivars were receptive to pollination after petal fall while the remaining pistils were no longer receptive in greenhouse studies. Any and all of these factors potentially influenced the amount of achene set and are collectively included in the flower-factor. Thus, there is considerable variation in the importance of the flower-factor both in different cultivars and within the same cultivar at different stages of flowering. Cultivars also appeared to differ in nectar production and attractiveness to in­ sects, a fact which ultimately influenced the total number of insect pollinators and the amount of insect pollination. A combination of short stamens, tall receptacles, and unattractiveness to insects attributed to an average 62% achene set in primary berries of the cultivar 'Redchief', while smaller receptacles and taller stamens in quaternary flowers resulted in 96% achene set. The 'Redchief' flowers were unattractive to insect pollinators throughout bloom when compared to other cultivars. As a result of the flower-factor, six commercial strawberry cultivars set from 46% to 70% of their achenes and four Michigan State University selections set from 56% to 90%. Insect pollination increased achene set to 90% or better in these cultivars. There was one exception: 48 'Midway 1' set 97% of its achenes without help from insects. Thus, insect pollination of 'Midway 1' was not important to the grower. Theoretically, the amount of pollination the flower-factor failed to accomplish was completed by the insect activity on the flowers. second pollination component is called the 'insect-factor'. This But insect species varied in their behavior on the flowers, and consequently, their pollination efficiency. Larger bee species, including the honey bee, contacted the stigmas and the stamens of a flower at the same time, so that the bee's movement resulted in pollination. Smaller bee species demonstrated a tendency to remain outside the tall stamens, and only occasionally touched the stigmas. Several species of Andrenidae and Halictidae were excellent pollinators of strawberry flowers and deserve continued study. Cultivars with short stamens permitted the small bees to contact stigmas and styles on the same visit. Various fly species appeared to differ from being occasionally pollinators to being of no value as pollinators of strawberry flowers. Pollinator density in commercial fields affected achene set. Honey bees were most numerous when colonies were located within or close to the field. Likewise, native bee species, most of which are ground nesting, were abundant only when nearby nesting sites were undisturbed. Andrenine and halictine populations were low in commercial fields surrounded by cultivated land unsuitable for nesting sites. Furthermore, if a field of strawberries had a low population of pol­ linators, the insects worked along the edges of the field, avoiding the middle, a fact supported by reduced levels of achene set in the center 49 of these fields. Pollinator insect populations were reduced during cold weather, rain, overhead irrigation, or periods of high wind. When other conditions were favorable to insect foraging except high wind, the insects foraged in areas protected by fence rows, woods, orchards, etc. Insecticide applications during bloom significantly reduced pollinator density, often for days. Insect control is important in Michigan strawberry production, but further study should be given to possible elimination of sprays during bloom. Loss of pollinating insects at bloom may be more serious than insect damage incurred during bloom. If insecticides are essential, sprays least toxic to bees should be applied when bees are not flying. For example, late afternoon and early evening application of an insecticide with less than overnight residual effect could almost totally prevent bee kill. The author worked in commercial fields where pollinator density was extremely low, yet there was no pollination problem. For growers had selected cultivars which did not need a great deal of insect pol­ lination for good berry production. In such cases elimination of pollinators by insecticides had little effect on final yield. But growers who practiced spraying in bloom could not be successful with cultivars which required insect pollination. Several growers in Van Buren and Berrien counties mentioned to the author that they had problems with either poor berry set or rough looking berries, both of which were a result of poor pollination indicated by low achene set attributed to low insect density. Usually these fields were sprayed in bloom, sometimes twice; also, the fields were surrounded by cultivated land which restricted nesting sites for native bee species, and there 50 were few colonies of honey bees within 1/4 mile of the field. Thus, when cultivars of the type benefited by bees were planted, a poor quality crop resulted. In addition to the danger of reduced pollinator density due to the use of insecticides, fungicides applied during bloom may have a deleterious effect on strawberry pollen fertility and germination. Some fungicides are phytotoxic to strawberry pollen (Eaton and Chen, 1968a, 1968b). As mentioned earlier, stamen height on different flowers in­ creased throughout the season, while receptacle height decreased, re­ sulting in proportionately higher achene set without the help of insects. For example, one field averaged 70% achene set in the primary flowers, 84% in the secondary flowers, 91% in the tertiary flowers, and 94% in the quaternary flowers. Because berries with 70 or 84% achene set had noticeable unpollinated areas and were less than perfect in shape, it was evident that the greatest need for supplemental pollination was during the bloom of these early flowers, while the need for insect pollination greatly decreased in the tertiary and quaternary flowers. In fields needing supplemental insect pollination, rental colonies of honey bees should be introduced at the first stage of bloom, but might be safely removed during the later stages, especially if an insecticide is to be applied. This research underscores the need for cooperation between plant breeders and entomologists in considering the pollination aspects of new cultivars. During past decades, strawberry breeders have striven for highly productive, hermaphroditic cultivars which set nearly 100% 51 of all the flowers on the stem. Generally, they have sought high yields, irregardless of the pollination requirements of the cultivar. In the process they may have rejected genetic stock because it failed to produce high yields where pollinator populations were low. Theoret­ ically, it is possible that breeders may have had good and poor pollen producing lines growing in small trial plots, with cross pollination from the viable pollen line increasing yield of the poor pollen line. In such a case, the problem of inadequate pollen production would not appear until the cultivar was grown in large acreages. When insect pollinators were excluded from trial plots, lines with poor morphological features but good yield and quality potential might be discarded. Finally, with the evolution of mechanical harvesters for strawberry production, cultivars will be required which concentrate flowering and ripening in order to optimize yield. In the greenhouse study it was evident that cultivars that remained in bloom longer set more achenes through self pollination; furthermore, the lines selected for concen­ trated ripening were open for shorter periods of time. This suggests that a short flowering period would greatly reduce self pollination in lines selected for concentrated ripening and increase the need for insect pollination. Pollination studies could help plant breeders become aware of the pollination requirements of new cultivars at the time of their release. Pollination requirements could then be specified for the growers benefit. Worthwhile research might consider the possibility of inter­ planting good pollen cultivars in the fields with cultivars lacking adequate pollen. Similar work could also be conducted investigating 52 the possibility of using pollen dispensors on colonies of honey bees to improve yields. Based upon counts of honey bees collecting pollen on different cultivars, there is a great difference in the level of pollen production or attractiveness of different lines. Controlled studies in greenhouse and field plots may provide additional information about these lines. To simplify the evaluation of strawberry pollination needs for growers, county agents, horticulturalists, beekeepers, and entomologists, a flow-chart is presented in Figure 11. This chart is a summation of the author's research and available literature. It provides a means of quickly checking the status of pollination in specific fields. Checking the height of the stamens relative to the receptacle is the key point in assessing pollination problems. Pollinator density is normally only a factor when stamens are shorter than the receptacle. An important part of the flow-chart is the change in appearance of the strawberry pistil after fertilization— changing from a green-yellow to a dark brown in color. Completely pollinated flowers show pistils of an uniform dark brown color at the end of anthesis, while incompletely pollinated flowers have a mottled appearance. In this research, fields of cultivars like 'Midway 1' seemed to have little or no need for insect pollinators for high yield of good quality. Fields with intermediate length stamens benefited from insect pollination but could not be said to warrant the expense of introducing honey bee colonies unless the local bee population was very low. Thus, only in cultivars with short stamens would this research suggest that supplemental pollinators be introduced on a regular basis. STRAWBERRY POLLINATION SYSTEM EVALUATION FLOW-CHART START CHECK STAMEN HEIGHT STAMENS TALLER THAN RECEPTACLE NORMAL BERRY PRODUCTION ATTRACTIVE TO INSECTS STAMENS SHORTER THAN RECEPTACLE CHECK POLLINATOR OENSITY CHECK POLLEN ABUNDANCE B "UNPOLLINATED PISTILS* OENSITY ADEQUATE ) CHECK CULTIVAR ATTRACTIVENESS IMATTRACTIVE TO INSECTS INCREASE POLLINATOR DENSITY-STOP SPRAYS IN BLOOM - ADD HONEY BEE COLONIES - INCREASE NATIVE BEES OKEY USE POLLEN OISPENSORS CHANGE TTMMG OF FUNGICIDE OR IRRIGATION INTERPLANT POLLEN SOURCE CHANGE CULTIVAR INCREASE POLLINATOR DENSITY CONSERVATION ENCOURAGEMENT Figure 11.— Flow-chart designed to allow growers, beekeepers, horticulturalists and entomologists to evaluate the level of pollination in specific fields. Remedial procedures are then suggested. 54 This analysis of strawberry pollination is far from complete: the complexities of flower morphology, pollinator behavior, pollinator density, etc., are interrelated with cultivar peculiarities, seasonal changes, climatic conditions, insecticidal applications, and cultural practices. However, the author hopes that this research has clarified the components of strawberry pollination and identified some of the more essential features. LITERATURE CITED LITERATURE CITED Allen, W. W. and S. E. Gaede. 1963. The relationship of lygus bugs and thrips to fruit deformity in strawberries. J. Econ. Ent. 56: 823-825. Anderson, W. 1969. The strawberry, a world bibliography 1920-1966. Scarecrow Press, Inc. Metachen, New Jersey. Bennet, M. 1968. Strawberry fruit malformation. II Role of disease and fungicides. Ann. Rept. E. Mailing Res 1967: 203-204. Brewer, J. W . , R. C. Dobson, and J. W. Nelson. 1969a. Effects of increased pollinator levels on production of the highbush blue­ berry Vacclnium corymbosum. J. Econ. Ent. 62: 815-818. Brewer, J. W. and R. C. Dobson, and J. W. Nelson. 1969b. Mechanical pollination of two highbush blueberry cultivars Vaccinium corymbosum. Hort. Science 4: 330-331. Brewer, J. W. and R. C. Dobson. 1969a. Nectar studies of the highbush blueberry Vaccinium corymbosum., cv. 'Rubel' and ’Jersey'. Hort. Science 4: 332-334. Brewer, J. W. and R. C. Dobson. 1969b.Pollen analysis of two highbush blueberry varieties Vaccinium corymbosum. J. Amer. Soc. Hort. Sci. 94: 251-252. Collison, C. H. and E. C. Martin. 1970. Competitive plants that may affect the pollination of pickling cucumbers by bees. Amer. Bee J. 110: 262. Connor, L. J. and E. C. Martin. 1970. The effect of delayed pollina­ tion on yield of cucumbers grownfor machine harvest. J. Amer. Soc. Hort. Sci. 95: 456-458. Connor, L. J. and E. C. Martin. 1971. Staminate:pistillate flower ratio best suited for the production of gynoecious hybrid cucumbers for machine harvest. Hort. Science 6: 337-339. Couston, R. 1966. Experiments on the influence of insect pollination on soft fruits. Scott. Beekeep. 43: 39-40, 90-92. 55 56 Darrow, G. M. 1925. The importance of sex in the strawberry. Heredity 16: 193-204. J. Darrow, G. M. 1927. Sterility and fertility in the strawberry Agric. Res. 34: 393-411. J. Darrow, G. M. 1966. The strawberry: history, breeding and physiology. Holt, Rinehart and Wilson, New York. 477 pp. Dorr, J. and E. C. Martin. 1966. Pollination studies on the highbush blueberry, Vaccinium corymbosum L. Mich. Agr. Exp. Sta. Quart. Bull. 48: 437-448. Eaton, G. W. and L.I. Chen. 1969a. The effect of Captan on straw­ berry pollen germination. J. Amer. Soc. Hort. Sci. 94: 558-560. Eaton, G. W. and L.I. Chen. 1969b. Strawberry achene set and berry development as affected by Captan sprays. J. Amer. Soc. Hort. Sci. 94: 565-568. Faegri, K. and L. van der Pijl. ecology. Pergamon Press, 1966. The principles of pollination New York. 248 pp. Fletcher, S. W. 1917. The strawberry in North America. MacMillan Co., New York. 234 pp. The Free, J. B. 1968a. The pollination of strawberries by honey bees. J. Hort. Sci. 43: 107-111. Free, J. B. 1968b. The foraging behavior of honey bees (Apis mellifera) and Bumblebees (Bombus spp.) on blackcurrent (Ribes nigrum), raspberry (Rubus idaeus) and strawberry (Fragaria x ananassa) flowers. J. Appl. Ecol. 5: 157-168. Free, J. B. 1970. Insect pollination of crops. New York. 544 pp. Gardner, V. R. Missouri Academic Press, 1923. Studies in the nutrition of the strawberry. Agric. Exp. Sta. Res. Bull. 57: 1-31. Horticulture Educational Association. 1960. crops. Sci. Hort. 14: 126-150. The pollination of fruit Horticulture Educational Association. crops. Sci. Hort. 15: 82-122. The pollination of fruit 1961. Hughes, H. M. 1961. Preliminary studies on the insect pollination of soft fruits. Exp. Hort. 6: 44. Janick, J. and D. A. Eggert. 1968. Factors affecting fruit size in the strawberry. Proc. Amer. Soc. Hort. Sci. 93: 311-316. 57 Knuth, P. 1906. Handbook of flower pollination. (trans. by J. R. Ainsworth-Davis.) Vol. II. Oxford, Clarendon. Kremer, J. C. 1949. Traps for the collection and distribution of pollen in orchards. Mich. Agric. Exp. Sta. Quart. Bull. 31: 12-2 1 . Kronenberg, H. G. 1959. Poor fruit setting in strawberries. I Causes of a poor fruit set in strawberries in general. Euphytica 8: 47-57. Kronenberg, H. G., J. P. Braack, and A. E. Zeilinga. 1959. Poor fruit seeting in strawberries. II Malformed fruits in cv. Jucunda. Euphytica. 8: 245-251. Lockhart, C. L. 1967. Effect offungicides on germination of lowbush blueberry pollen and number of seeds per berry. Can. Plant Dis. Survey 47: 72-73. Mangelsdorf, A. J. 1927. 18: 177-184. Origin of the garden strawberry. J. Hered. Marshall, G. E. 3954. The effect of rain and applications of fungicides and insecticides on the catfacing of strawberries. Proc. Indiana Acad. Sci. 64: 136-139. Martin, E. C. 1966. Honey bee pollination of the highbush blueberry. Amer. Bee J. 106: 366-367. Mitchell, T. B. 1960. Bees of the Eastern United States. Agr. Exp. Sta. Tech. Bull. 141. Mommers, J. 1961. De bestuiving Dir. Tuinb. 24: 353-355. N. Car. van aardbeien onder glas. Meded. Moore, J. N. 1964. Duration of the receptivity to pollination of flowers of the highbush blueberry and the cultivated strawberry. Proc. Amer. Hort. Sci. 85: 295-301. Moore, J. N. 1969. Insect pollination of strawberries. Hort. Sci. 94: 362-364. J. Amer. Soc. Nitsch, J. P. 1950.Growth and morphogenesis of the strawberry as related to auxin. Amer. J. Bot. 37: 211-215. Nitsch, J. P. 1952. Plant hormones in the development of fruits. Quart. Rev. Biol. 28: 33-57. Percival, M. S. 1955. The presentation of pollen in certain angiosperms and its collection by Apis mellifera. New Phytol. 54: 353-368. 58 Petkov, V. 1965. Studies on the role of bees in strawberry pollina­ tion. Gradinar. Iozar. Nauka 2: 421-431 (in Bulgarian, seen in Apic. Abst. 791/68). Rajput, C. B. S. and J. P. Singh. 1967a. Pollen studies in straw­ berries. HorticulturalistSrinagar 2: 47-51. Rajput, C. B. S. and J. P. Singh. 1967b. Pollination and fruit setting studies in strawberries. Indian J. Hort. 24: 30-32. Robbins, W. W. 1931. Botany of crop plants. Philadelphia. 674 pp. McGraw-Hill, New York, Skrebtsova, N. D. 1957. The role of bees in pollinating strawberries Pchelovodstvo Vyatka 34: 34-36. Translated by N. V. Ponomareff Sokal, R. R. and F. J. Rohlf. 1969. Biometry— The principles and practice of statistics in biological research. W. H. Freeman and Co., San Francisco. 776 pp. Swarbrick, T. and Thompson, C. R. 1933. Some observations upon the partial self-sterility of the Oberschlesien strawberry and its failure to pollinate Xardive de Leopold. Rep. agric. Hort. Res. Stn. Univ. Bristol 1932: 24-31. Thompson, P. A. 1971. Environmental effects on pollination and receptacle development in the strawberry. J. Hort. Sci. 46: 1-12. Thompson, W. W., J. Hull, A. L. Jones, A. J. Howitt and C. W. Laughlin 1972. 1972 Fruit Spraying Calendar. Extension Bulletin 154, Farm Science Series, Cooperative Extension Service, Michigan State University. Way, D. W. 1968. Strawberry fruit malformation. I. Polological aspects. Ann. Rept. E. Mailing Res. Sta. 1967: 199-203. Figure 12.— Various aspects of floral morphology of strawberry flowers. A— ’Redchief, with tall receptacle and shorter stamens; B— 'Guardian', also with stamens shorter than receptacle; C— Honey bee on flowers with stamens approximately equal in length to stamen height; D— 'Midway 1' flowers with stamens taller than receptacle; E— honey bee on flower with stamens equal in length to stamen height; and F— flower at the end of anthesis, loosing petals, with pollinated pistils darkening. 60 61 Figure 13.— Various degrees of pollination. A— Only 2 or 3 pollinated and enlarged achenes; B— about 10 enlarged achenes producing nubbin or button shape, note small size of unfertilized ovules. C— Random achene enlargement from self-pollination; D— Nearly complete pollination, with only a few unpollinated ovules in creases and at berry tip; E— Pistillate 'NJ 264'; hand pollinated after petals had fallen, showing pistil receptivity only at tip of receptacle (berry); F— 'Guardian' berries resulting from self-pollination, with characteristic nubbin or button appearance. Figure 14.— Honey bee activity on strawberry flowers. A, B, and C— shows a single bee visit to a flower with bee following a clockwise direction. The bee is centered over the top of the receptacle during much of the visit. D and E— honey bee touching pistil and stamens during same visit. F— Honey bee on pistillate flower, seeking nectar. Figure 15.— Several native bees on strawberry flowers. A and 15--Andrenine on top of receptacle. C and D— Halictines working anthers from outside of 'wall' of stamens, eliminating most contact with pistils and thus minimizing pollination. Figure 16.— Typical flower stems from open pollinated plots, screen covered plots, and cloth covered plots, representing insect, self and wind-motion pollination respectively. A, B, C— 'Sunrise': open screen, cloth cages, respectively; D, E, F— 'Midway 2' open, screen, cloth respectively. '•*0 ft/. Figure 17.— Similar to Figure 16, with 'Redchief' A, B, C— open pollination, screen cages, and cloth cages respectively; D, E, F— open pollination, screen cages, and cloth cages for 'Guardian', respectively. TTpw Figure 18.— Short stamened 'Surecrop' yield in open pollination plots (A) and screen covered plots (B) compared to cloth covered cage of tall stamened 'Midway 1' (C). In D, E, F, Primary berries of 'Redchief' that were harvested at 0, 75 and 150 feet from the edge of a field with low pollinator density, showing poorer berry quality in the center of the field. There was a 20% decrease in the level of achene set from the edge to the center of this field. APPENDICES 73 APPENDIX I field locations, and dates of cage placement and removal GROWER CULTIVAR REPLI CATI ON Cu 1by Cu 1by Pi ggott Pi ggott Pi ggott Radewa 1cl Radewa id MSU Hort. D e p t . MSU Hort. D e p t . MSU Hort. D e p t . MSU Hort. D e p t . Hassel1 Hassel1 H a s s e 11 Lutz Lutz Lutz Lutz Lutz Sunri se M idway 2 Sunri se Ear 1idawn Mi dway 2 Redchi ef M idway 2 M 828 M 788 M 766 M 772 Sunri se Redchi ef Guardi an Surecrop Redchi ef Sunri se Midway 1 (Early Mi dway) Midway 2 (Reg. Midway) 2 2 2 2 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 for 1971 cage study. CAGES PLACED May 6 May 6 May 6 May 6 May 6 May 6 May 6 May 13 May 13 May 13 May 13 May 6 May 6 May 6 June 2 June 2 June 2 June 2 June 2 11 11 7 7 11 15 11 2k 2k 2k 2k 11 11 15 25 25 25 25 25 APPCNMI I I P A I A A A T ho. w h o rr< o t 1 o c fc v t to t • 1 A A 1 ( S S tv te r * w • rrp r trc.fr, X S C C 0 ■ •o . h p r r lc t t • C A A l t S 0 A Ay S tv A n rC W w •rrs r n c h v * c r e tin % pchvp M l M l T C A T1A AV 0 1 ■ 8 l I S w ItvAprO Op . w •rrpr Perrim T achvp irti<* 1 Mt P C h V Mt •917 -757 .9* 1059 *9 .059 •01 ) .015 •01) 151 *9 *7 H7 *.63 5).17 79.76 60.91 .6)1 .8(7 1.184 895 .810 .784 921 t.450 1.049 .022 .0)0 .016 .022 64 7* a US 64.91 44.04 *.65 76.95 9)7 928 1.444 1.070 .021 •0 * on .024 27* *9 ID 646 48.). W . 87 97-92 7).* .7*9 .016 1.424 1.028 .017 .on .01) 74.16 59.75 .116 .*2 1.0)7 .*) -0)0 .025 .024 .017 47 5' 42 Ito 50.44 47 51 72.12 4)47 792 945 1.015 922 .0)1 .026 .027 .OH 250 27) H' 764 47.92 *2) 64 74 5J.70 .745 .7* 954 .822 .010 09.S9 99 71 99.00 *.1* 94 91 95 2* 49.04 54181 89.59 67.05 .774 .854 1.242 .959 .0)0 .024 .022 .0*9 82 7* 75 2)* 57.02 49.)) 91-44 7).47 .854 ■9 * '.274 '.012 .028 .021 .026 .0*9 *4 *8 )I7 9)1 4).7) 46.49 86.H 41.15 72) .770 1.191 .8* .017 .017 .014 .812 89.85 99 7* IQ0.00 96 46 .027 .026 .025 .021 90 91 94 277 55.54 73.79 95.* 78.* .841 1.03) i.*9 1.087 .0)0 •02) •019 •019 44 68 79 713 60.* 78.59 95.84 81 .* 8* 1.090 >.*5 ’->>2 -0)2 .027 .020 020 2* 297 )2J 916 50.89 67.02 95 0) 74.52 79* 959 t.*4 1.042 .016 .014 .01) .012 91 .to 93*39 *.37 **9 .827 • 914 i .H I ■051 .0 )8 .024 •019 023 * 9) 79 258 41.47 74.52 97.37 *.04 .90) 1.042 l.al i.1* 0)9 .020 .021 .021 59 67 59 <85 61.0) 79 68 97.21 83.78 97C i.'O) '.* 3 >.<54 .042 .017 .026 .02) 272 *8 25* 6)1 59 25 64.55 97S) 74.77 .178 95* *•41) 1 .0 a .021 .015 •01) .012 a . 32 *71 99.32 93.85 40.10 87.69 99 61 8 5 .) i .684 1.212 <-508 t.1 7 7 .024 .027 .0 *6 .024 50 1) 94 227 37.72 85-84 99.96 a. >6 .441 1.185 1.5*7 i.H9 .029 •0J1 009 .024 10 20 57 87 42.18 83.S7 99-69 *.72 .707 >15) '.S'S ' )J9 .08* .05* 026 .0* 144 2* *l 70) 40.02 84.71 99-44 86.59 .US i.*69 1-4* M * .017 .020 .812 .015 78.09 97.)) 100.00 92.* 96 97 50 24) 50.56 90.42 9 5 .* 79-12 792 1.240 l.) 4 4 1.096 .025 .026 .024 .022 a 95 50 2)) 48.65 91.44 *.6l *.09 .772 1.274 1*4 1.108 .024 .027 .025 .02) 67 49 17* 49.7* 91.05 97.97 81.25 .762 t.285 1.428 '-*2) .0* .0* .028 829 297 *5 *4) 745 49. *5 90.86 95-52 76.a .776 1.250 l.)58 1.090 .015 .016 .016 .01) *.51 99-16 99-08 97-)* .027 .0 )0 .0 5 ' .033 8< 94 94 27) 2 ) .M 4 4 .* 9 1 .5 ) S7.22 .5 *0 .7 )) 1.275 .858 .021 .021 ■0)1 .024 90 92 94 276 37.54 67.12 *.92 71.* 440 .9* I.)* 1.01) .024 .020 .022 .022 77 7* 9* 242 5)65 76.0) *69 *.57 .822 ‘.08 ) <.456 l.<40 02) 019 020 02> 28) 304 320 *7 JS-24 58.67 *.76 67 65 6* •87) i.*e 96* .016 .014 .016 01) 17.64 99.H 97.92 *.25 .401 .444 1.049 .784 .050 .0)1 .0)1 .0 )8 79 12 78 2)9 44.42 35.74 17.11 54 IS 729 .441 1.205 .854 .0 )2 .024 .024 .022 94 1* 78 274 6 1 .)l 58.81 93.12 71.33 .899 .674 1.105 1.004 .OH .0*9 .020 .017 * 97 71 2* 76.* 73.14 92.* 81.41 1.09) >.026 1.)00 >.125 0*8 014 02) 01) 2* 2* 245 851 5*.64 09 46 66.65 •*90 .8)2 1 .2a .979 .017 .015 01) .011 a.17 92.29 i a .00 91.*3 48.27 73.28 98.11 72-98 .748 l .028 I.4 J J 1.024 .055 .049 .044 .048 ) 100 41 224 5 ).6 4 47.41 99.78 71.02 .822 .9 4 ) 1.524 1.01) .024 .0 24 .018 .022 100 99 49 246 57.* 68.2) 99.* 74.4) .864 •972 1.551 1.0*) .019 •019 .011 .020 15 81 *4 2*2 44.4) 70.03 99-92 76.* .0)2 .991 1.5*3 1.087 .017 Oil .0*4 •019 291 329 150 770 99.1) 7*.H .64* .*2 >.5)0 1.0*4 .012 .013 .009 .011 100.00 100.00 100.00 >00.00 41 41 )J IIS 43.81 58.98 85.02 41.02 • 723 .874 i.» 7 ) .907 .0)1 .0 )3 029 .025 94 It 44 24) 54.54 7 J .7 I 6S 93 71.04 .851 1.0)2 1.184 1.80 ) .0 2 ) .016 .016 .014 87 72 57.11 *.10 87.» 74.1) .016 281 2* 207 7* .*) 77.65 .8* 1.14* 1.227 1.076 .021 a.* .016 57 5* *7 (58 *.77 62.* 1.210 1.0)7 .02) .021 .017 2* .01) .012 .010 .009 100.00 61.65 C lo th Scroon Opv Avoropo 24 45 49 III 48.57 4 4 .lt 83 .9 4 70.12 .771 929 1.159 991 .052 .029 .0)1 .024 45 98 100 2 4) 70.75 70.42 19 .2 4 79-07 .999 996 1 .1)7 1.094 .021 .014 .017 01) •971 1.0(1 1.2*3 1.1* .02* •0(9 .017 .014 92) 1.01) l 290 295 7* •9.2} 1.118 .04) .822 .822 .819 6*.* 70.27 59 1*0 6) .6) n.* *.3) *18 16) 87 205 C lo th S e ro v 40 44 19 105 44 .8 4 4 4 .J I 7 9 .J I S '.IO .7 )4 .728 1.099 .797 .050 .0 )9 .044 .029 90 99 60 229 48 .4 9 71.21 98.41 47.42 770 1.004 1.896 9 6) .0)1 .028 .0 )9 .022 .8* 0)2 .0)1 .0)) .a* 4).5* *.4* 99* 83.28 ■922 1.166 1.487 1.1*9 .0)9 .827 .028 .OH 274 2* 1)5 70) *.2) 72.61 *.*2 71.70 14 41 42 124 52.88 51.45 95 .1 2 44.12 .411 .100 1.J48 •928 .040 .045 .0 )7 .0 )4 75 9) to o 248 )9 2 l $7.87 97.50 78.27 .477 .864 I.4 U 1.016 •0 *7 .0 19 .0 (6 .0 2 ) *6.*0 7).* 99-tl 79.48 •7*9 1.03* t.477 1.10) 6)5 .0)6 .018 829 2*1 285 2* 824 *1.17 62-70 *.29 7*.*l .420 .544 I.U 5 80) .041 .0)1 .0 )0 .031 61 95 98 254 10.87 45.58 62.75 57 . * 589 741 i.th ) .159 .027 .021 .017 019 41 94 92 227 J4.07 a . 92 771) 42.97 C lo th Scrooo Opv A voropr * 45 * 129 41.57 54.10 94.17 7112 .701 .854 '.3 7 6 1.005 .0 6 : 052 0)> .0 )7 84 99 too 285 J4.80 58.01 97 49 70.16 .452 .844 1.412 .9 9 ) .027 .028 .0 2 1 .024 04 94 67 247 49-90 4).)S 91.55 75.11 C lo th S e rv e O pv Avprcpa h$ 4? h9 th l 4 J .I7 2191 SJ.7J 41.92 .717 .548 82) .704 .0 )6 0)8 0)7 .023 84 94 95 273 44. n J6-76 44.70 49.57 729 .672 9)5 .781 .0 )0 0 )0 025 OH 74 11 75 2)0 53.09 C lo th S e rv e Opv A«or*p> hi 4 h9 I* 26.74 20.81 71.25 40 .4 4 54) .475 1.027 .691 .045 .026 0)5 .0 )0 89 95 58 282 ) 4 .] 2 )5 .0 4 84.02 54.25 .424 .675 1.160 .828 .0 )2 .0 )0 .024 .022 C lo th S c rc v Open A v tn p r 47 45 61 140 J4.82 35-79 91-12 56.72 .6)1 .64; 1.268 .8 5 ) 0)9 .0 )7 .044 .0 )4 95 9) 100 288 47.44 65.45 95 0 ) 72.a .740 945 i.) 4 6 1.02) C lo th Scroon O pv Avo'O pt J9 49 32 <20 51.47 37.99 93.44 59.72 .800 .644 i .320 .8 8) • 052 .0 )8 .048 .0 )6 88 99 8i 268 54.20 42.75 9 6 .* 75 )6 C lo th Scroon Qpon JO 40 SO 120 42.98 74.49 95.28 78.54 .715 1.041 1 )5 2 <.089 .045 .044 .047 .0 )9 74 95 ■00 269 C lo th Scroon Opon A vo ro pt 44 44 25 US 47.21 81.21 85 .5 9 49.13 .758 1.122 l.llt .989 .0 )9 .0 4 ) .050 .0)1 1 C lo th Scroon Opon A v o ro pt JS 42 J7 114 19.24 34.46 78.09 4 J .7 I -454 .428 1.084 .722 AMchiaf Nm m II C lo th Scroon Opon Avoropo 2J 19 Jt •0 J 2 .0 I 18.44 74.87 50.08 C lo th Scroon Opv Aoorapo 2J 49 14 * C lo th Scroon Opon Avoropo n iO v y 2 Cwlhy OM" A v o rp ^ movy * uti * . 6) 92-51 95-22 78 53 47-21 *9.*9 75-99 49 84 JJ-74 24.99 12.16 51.74 C lo th S e ro v A v ro « i 6 61 a * 84 51 .a a.ii *1.6) 89.44 79.61 99 111 57.99 79.D 97 61 74.22 77 4).a a 140 64.51 99.17 77.67 86 a .444 .875 1 .0* .857 ua 1.0* 1.416 1.041 .7* .9* t.US 1.879 -027 .018 .0(6 .02) * 21 * * 41 37 1* S3 * 41 170 *.a .018 .022 a.» .a 57 49.20 55 76 75.* a.* 72.10 78.11 •8* 1.05J 1.200 1.014 .016 P CA c 1 ■ s 0 1 11 y 19 78 48 145 JO hi *9 III lult T 0 T A I or a 11 8 1 8 A 1 C S SlP*rt P PV •0 . « M 6«rrl«» X achvp •rctln X •rrpr ft! t c h v M8 .018 .027 .018 244 387 287 858 5>.40 7 1 .5 * 91.20 73.42 .799 1.008 1.270 1.031 .012 .o n .012 .0 89 8 1 .4 9 91 .7 4 9 8 .4 8 90.53 C lo th Scroon C^on Average >8 41 23 !• 51.23 55 04 97.53 49- 34 • 798 ■834 1.413 .984 950 •030 0>9 034 S' 82 48 ■81 41.00 41 .7 4 99 .3 4 75.89 ■194 984 1.491 1.857 .025 .001 .004 .0 04 49 43 45 • 57 40.17 47.17 99 .5 4 79.41 .908 .941 1.503 1.100 .031 .025 .025 .024 21 38 35 94 ( 4 .0 4 70.04 99-50 84.88 .949 •992 1.500 1.171 .044 .030 .008 .032 139 224 150 513 40 .9 4 43.53 99.27 77.74 .894 .922 1.485 1.080 .017 .013 .914 .014 43.27 4 4 .3 9 93.27 43 .8 4 C lo th S e ro v Opon A v t 'iy i 40 77 77 108 44 .0 9 78.SS 78.55 51.04 .724 837 ■837 • 794 • 039 ■034 ■034 .024 88 143 143 23' 54.74 45 .2 8 45.28 42.07 .853 .941 .941 .907 .810 .8 23 .003 .017 92 735 135 227 47.27 72.34 71.34 70.32 .942 1.017 1.017 •995 023 .021 .021 .0 14 43 77 77 140 70.18 78.55 78.55 74.90 .993 1.089 I .* 9 1.044 .031 030 030 022 *83 423 423 704 41.52 48.55 48.55 45.77 .982 ■975 •975 944 .0 )4 013 .01$ .010 87 .9 4 94 .1 2 94.12 91 .5 7 C lo th Scroon *m Average 25 32 SO 107 93.48 98 .5 8 97.17 97-00 1.317 1.451 1.402 1.397 .848 035 .088 .821 41 83 108 244 83 .4 9 94.50 99.78 94 .5 4 1.155 >■383 '.5 2 4 I.J 8 4 .095 .013 .012 .014 n 98 99 255 74.87 97.57 99.91 95.75 •.0 4 9 1.414 1.540 1.343 .084 .022 .012 .017 57 73 74 104 44 .7 4 94.37 99 .9 9 93 .0 4 • 93$ 1.331 1.542 1.304 033 -027 .004 .022 215 278 317 810 78.34 98.87 99 73 95 58 1.087 1.38? 1.519 1.359 .018 .013 .007 .0 89 9 3 .2 4 94 .8 9 100.08 94.55 *Su nSu NIOk*y 1 L a tf .023 .017 76 APPENDIX I I I Source and description of 10 cultivars used in 1971 greenhouse evaluations. SOURCE CULTIVAR COMMENTS: Den ison, 1owa Stopli ght High Deni son, 1owa 133-6733 Higher Deni son, 1owa 7-6736 Highest Smith, Rutgers NJ 264 Pistil late selecti on Moulton, MSU M idway* A leading Michigan producer. Moulton, MSU Guardi an USDA release, disease resistant Moulton, MSU Sequoi a C a 1i forni a Moulton, MSU Surecrop Moulton, MSU Redchi ef Commercially available, disease resistant,but not a leading line. USDA release, disease resistant Moulton, MSU Ti oga Good producer in California *Midway was not designated either Midway level of concentrated ripening. level of concentrated ripening than Stoplight. level of concentrated ripening. 1 or Midway 2 by Moulton's supplier, but appeared to by Midway 2. 77 A P P E N D I X IV Parameters concerning sweep net collections made in 1969 - 1971. Materials, preserved and stored at the Department of Entomology, Michigan State University, may be identified by year of collection and sample n umb er. SAMPLE C U L T I VAR 1 2 3 4 5 6 7 8 9 10 11 12 13 i4 13 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Wi Id Wi Id Mixture Wi Id Mi xture Mi xture Mi xture Mi xture Unknown Midway 1 Mixture Mi xture Mi xture Mixture Mi xture Mi xture Mi xture Mi xture Mi xture Mi xture n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r 3k 35 DATE TIME (EST) O k May 1200 O k May 0200 06 16 16 23 2k 2k 26 26 26 26 27 28 28 28 28 28 28 28 29 29 29 29 29 29 29 29 29 29 06 06 06 31 10 May May May May May May May May May May May May May May May May May May May May May Hay May May May May May May Jun Jun Jun May Jun 0115 1115 0200 0300 0230 0330 1200 0130 0300 0330 1200 0100 0115 0130 0145 0200 0215 0230 0900 0900 1000 1000 1000 1000 1100 1100 1130 0200 0115 0200 0400 0200 1100 OWNER TEMPERATURE °F 1969 Connor Connor Hort Farm Apiary Lott Hort Farm Hort Farm Lott Kayes Fos terBrs. Connor Beauchamp A1fonso Lutz Lutz Lutz Lutz Lutz Lutz Lutz Grant Grant Grant Grant Grant Grant Lather Lather Lather Lutz Grant Lather Lutz Col 1ison Hort Farm 75 75 75 78 83 62 72 72 65 70 70 70 75 85 85 85 85 85 85 85 60 60 62 62 64 64 66 66 66 78 63 60 58 82 68 WIND MPH 05 05 25 05 n/r 25 25 25 00 20 15 20 25 20 20 20 20 20 20 20 25 25 25 25 25 25 30 30 30 25 25 25 25 n/r 20 PERCENT SUN 100 75 75 100 100 25 100 100 90 90 90 90 70 100 100 100 100 100 100 100 00 00 25 25 75 75 100 100 100 100 100 100 70 100 100 NUMBER SWEEPS n/r* n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r n/r 78 A p p en d ix SAMPLE 1 2 3 4 5 6 7 8 9 10 11 12 13 lit 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 3k 35 36 37 38 39 ko k) kl k3 IV (c o n t'd ) CULTIVAR DATE T IM E (E S T ) Ear 1idawn Sunri se Sunri se Ea r 1idawn M idway 2 Redchi ef Redchi ef Redchi ef Wi Id Midway 2 Mi dway 2 Midway 2 Mi dway 2 M idway 2 Midway 2 M idway 2 Mi dway 2 Midway 2 Mi dway 2 M idway 2 Midway 2 Midway 2 Robi nson Midway 2 Midway 2 Midway 2 Mi dway 2 Midway 2 M idway 2 Midway 2 M idway 2 M idway 2 Midway 2 Midway 2 Midway 2 M idway 2 M idway 2 Mi dway 2 Midway 2 M idway 2 Midway 2 Redchi ef Ea r 1idawn 5 5 5 5 5 5 5 5 7 8 8 8 8 8 8 8 8 8 8 8 8 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 1045 1100 1145 1200 1200 0145 0155 0205 1200 0300 0315 0325 0340 0345 0355 0405 0415 0440 0445 0500 0505 0915 0945 1000 1015 1030 1100 1100 1100 1130 1145 1215 1230 0100 0115 0145 0200 0245 0330 0345 0400 0430 0500 May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May OWNER TEMPERATURE °F 1970 Pi ggott Pi ggott Pi ggott Pi ggott Pi ggott R a d e w a 1d Radewa 1d R a d e w a 1d Connor Dowd Dowd Dowd Dowd Dowd Dowd Dowd Dowd Dowd Dowd Dowd Dowd Dowd FosterBrs. FosterBrs. F o s t er Brs. FosterBrs. Bai ers Bai ers Bai ers Scherer Scherer Bai ers Bai ers Bai ers Scherer Hassel Hassel Dowd R a d e w a 1d R a d e w a 1d R a d e w a 1d R a d e w a 1d Pi ggott 69 69 69 69 69 72 72 72 58 70 70 70 73 73 73 73 73 75 75 75 75 75 75 75 75 75 78 78 78 80 80 82 82 82 82 82 84 84 85 85 85 85 80 WIND mph 12 12 12 12 12 18 18 18 18 18 18 18 18 18 10 18 18 20 20 20 20 23 23 23 23 23 28 28 28 23 23 23 23 23 23 23 23 23 25 25 25 25 20 PERCENT SUN NUMBER SWEEPS 80 80 80 80 80 50 50 50 80 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 i00 100 100 100 100 100 100 100 100 100 100 100 100 100 n/r n/r n/r n/r n/r 500 500 500 n/r n/r 340 340 350 350 350 350 350 300 300 360 360 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 79 A p p e n d ix .AMPLE 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 IV (c o n t'd ) CULTIVAR DATE Sunrise 19 Midway 2 19 Midway 1 20 Midway 2 20 Midway 2 21 Midway 2 21 Midway 2 21 Redchief 21 Redchief 21 Redchief 21 Redchief 21 Redchief 21 M idway 2 21 M idway 2 21 Midway 2 21 Midway 2 21 Sunrise 21 Midway 1 21 Midway 2 21 Earli dawn21 Sunrise 21 Midway 2 21 M idway 1 Midway 2 Midway 1 Midway 2 Midway 1 Midway 2 Midway 2 28 Midway 2 29 Midway 2 29 Midway 2 28 Midway 2 29 Mi dway 2 29 Midway 2 29 Midway 2 29 M idway 2 29 Midway 2 29 Midway 2 29 Midway 2 29 Midway 2 29 Midway 2 29 May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May TIME (EST) 0505 0530 0230 0230 1030 1045 1055 1225 1215 1235 1245 1255 0115 0130 0145 0155 0230 030 0 0315 0315 0340 0355 0900 0900 1030 1030 0300 0300 1245 1045 1100 1130 1130 1145 1215 1230 0130 0145 0200 0215 0230 0245 OWNER TEMF ^RATURE Pi ggott Pi ggott Col 1ins R d . Col 1ins Rd. Dowd Dowd Dowd R a d e w a 1d R a d e w a 1d R a d e w a 1d R a d e w a 1d RadewaId R a d e w a 1d RadewaId RadewaId RadewaId Cu 1by Culby Cul by Pi ggott Pi ggott Pi ggott Col 1ins Rd. Col 1ins R d . Col 1ins Rd. Col 1ins R d . Col 1ins R d . Col 1ins R d . Col 1ins Rd. Dowd Dowd Dowd Dowd Dowd Dowd Dowd Foster Br. Foster Br. Foster Br. Foster Br. Bai ers Ba iers 78 75 78 78 79 79 79 85 85 85 85 85 85 85 85 85 86 86 86 85 85 85 72 72 74 74 75 75 65 75 75 79 79 79 79 79 83 83 83 83 83 83 WIND mph 20 20 13 13 18 18 18 16 16 16 16 16 16 16 16 16 18 18 18 20 20 20 18 18 18 18 25 25 23 18 18 18 18 18 18 18 28 28 28 28 30 30 PERCENT SUN NUMB SWEE 100 100 95 95 95 95 95 95 95 95 95 95 95 95 95 95 100 100 100 100 100 100 50 50 50 50 75 75 100 85 85 85 85 85 85 85 90 90 90 90 90 90 500 500 n/r n/r 500 500 500 400 400 400 400 400 500 500 500 500 500 500 500 500 500 500 n/r n/r n/r n/r n/r n/r n/r 500 500 500 500 500 500 500 500 500 500 500 500 500 80 A p p e n d ix SAMPLE 1970 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 L IV (c o n t'd ) CULT 1VAR DATE (cont1d) Midway 2 29 May Midway 2 29 May Midway 2 29 May Midway 2 29 May M dway 2 29 May M dway 2 4 June M dway 2 4 June M dway 1 4 June M dway 2 4 June M dway 1 4 June M dway 1 4 June M dway 2 4 June M dway 2 4 June M dway 2 4 June M dway 2 4 June M dway 2 4 June M dway 1 4 June Surecrop 4 June Midway 1 4 June Sunri se 4 June Paymaster4 June M dway 2 4 June M dway 2 4 June M dway 1 4 June M dway 2 4 June M dway 2 4 June M dway 2 4 June M dway 2 4 June M dway 2 4 June M dway 2 4 June M dway 2 4 June M dway 2 4 June M dway 2 4 June M dway 1 4 June M dway 1 4 June M dway 2 5 June M dway 2 5 June M dway 2 5 June M dway 2 5 June M dway 2 5 June M dway 2 5 June M dway 2 5 June M dway 2 5 June M dway 2 5 June M dway 2 5 June M dway 2 5 June TIME (e s t ) 0245 0245 0330 0345 0415 1030 1030 1030 1030 1 100 1 100 1115 1115 1130 1130 0130 0130 0200 0200 0210 0210 0220 0220 0250 0250 0300 0300 0400 0400 0415 0415 0430 0430 0500 0500 0800 0800 0830 0830 0850 0900 0900 0915 0915 0930 0930 OWNER TEMPERATURE °F Scherer Scherer Bai ers Bai ers Scherer Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lather Lather Lather Lather Lather Ruph Ruph Ruph Ruph Lather Lather 85 85 85 85 73 69 69 69 69 69 69 70 70 70 70 70 70 70 70 72 72 72 72 72 72 72 72 74 74 74 74 74 74 74 74 55 55 55 55 55 55 55 58 58 59 59 WI ND mph 30 30 30 30 28 05 05 05 05 05 05 05 05 05 05 08 08 08 08 12 12 12 12 12 12 12 12 18 18 18 18 18 18 18 18 05 05 05 08 12 10 10 10 10 15 15 PERCENT SUN NUMBE SWEEP 85 85 90 90 10 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 81 A pp e n d ix IV SAMPLE (c o n t'd ) CULTIVAR 1970 (cont'd) M dway M dway M dway M dway M dway M d wa y M d wa y M d wa y M dway M d wa y M dway M dway M dway M dway M dway M dway M dway M dway M dway M dwa y M dway M dway 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 1971 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 DATE L. 5 Jun e 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 1 2 1 1 Wi Id Sunri se Midway 2 Midway 2 Midway 2 Sunri se Sunri se Sunri se Sunri se Sunri se Midway 2 Midway 2 Redchi ef Redchi ef Sunri se Sunri se Sunri se Sunri se Sunri se Sun ri se Sunri se Sunri se 5 5 5 5 5 5 5 5 5 >c 5 5 5 5 5 5 5 5 5 5 5 13 13 13 13 13 13 13 13 13 13 13 13 14 14 14 14 14 14 14 14 14 14 T IM E (E S T ) OWNER June June June June June June June June June June June Jun e June June June June Jun e June June June Jun e 1015 1015 1045 1045 1045 1045 1130 1 130 1 145 1145 1200 1200 0230 0230 0300 0300 0330 0330 0430 0430 0430 0430 Grant Grant Grant Grant Grant Grant Grant Grant Grant Grant L a t her L a t her Cudney Cudney Howe Howe Howe Howe Lutz L ut z Lutz Lutz May May May May May May May May May May May May May May May May May May May May May May 1115 0100 01 10 0115 0130 0135 0215 0230 0245 0300 0305 0315 1030 1045 1130 1145 1145 1200 1200 1200 1215 1215 1971 So.Haven Cul by Culby Culby Cu 1by Cul by Pi ggott Pi ggott Pi ggott Pi ggott Pi ggott Pi ggott R ade wa1d Radewa1d Pi ggott Pi ggott Pi ggott Pi ggott Pi ggott Pi ggott Pi ggott Pi ggott TEMPERATURE °F WIND mph PERCENT SUN NUMBER SWEEPS 65 65 65 65 65 65 69 69 71 71 73 73 75 75 75 75 75 75 75 75 75 75 20 20 20 20 20 20 08 08 08 08 23 23 28 28 28 28 28 28 28 28 28 28 100 100 100 100 100 100 100 100 100 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 500 60 66 66 66 66 66 66 66 66 66 66 66 62 62 05 20 20 20 20 20 20 20 20 20 20 20 05 05 10 10 10 10 10 10 10 10 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 n/r 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300 50 50 50 300 300 63 63 63 63 63 63 63 63 100 100 100 100 100 100 100 100 100 100 100 100 82 A p p e n d ix IV SAMPLE 1971 23 24 25 26 27 28 29 30 31 32 33 Ik 35 36 37 38 39 ko kl 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 (c o n t'd ) CULTI VAR (cont'd) M idway 2 Mi dway 2 Sunri se Sunri se Sunri se Sunri se M idway 2 M idway 2 Midway 1 Midway 1 Midway 2 M idway 2 M idway 2 Midway 2 Midway 2 M idway 2 M idway 2 Midway 2 M idway 2 M idway 2 Mi dway 1 Mi dway 1 M ?dway 2 Midway 1 M idway 1 Mi dway 2 Redchi ef Redchi ef Redchi ef Redchi ef Redchi ef Redchi ef Midway 2 Mi dway 2 M idway 1 Midway I Midway 1 M idway 2 Sunri se Sunri se Wi Id Sunri se Midway 2 Mi dway 2 Mi dway 2 Sunri se Sunri se DATE 14 14 14 14 14 14 14 14 14 14 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 17 17 17 18 18 18 20 20 20 20 20 20 20 May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May May T IM E (E S T ) 1245 0200 0330 0345 0355 0410 0430 0440 0450 0500 0900 0900 0900 0900 0930 0930 0930 1000 1000 1000 1045 1045 1045 1130 1130 1130 0100 0100 0130 0130 0130 0130 0230 0230 0300 0300 0300 1030 1130 0200 1100 0100 0100 0100 0100 0100 0200 OWNER TEMPERATURE °F Pi ggott Culby Hassel Hassel Hassel Hassel W m Foster W m Foster W m Foster Wm Foster Foster Br Foster Br Foster Br Foster Br Foster Br Foster Br Foster Br Foster Br Foster Br Foster Br W m Foster W m Foster W m Foster W m Foster W m Foster W m Foster RadewaId RadewaId RadewaId RadewaId RadewaId R a d e w a 1d RadewaId R a d e w a 1d Collins Rd Col 1ins Rd Collins Rd Foster Br Hassel1 Pi ggott So. Haven Cul by Culby Cul by Culby Culby Pi ggott 63 65 72 72 72 72 72 72 72 72 65 65 65 65 73 70 70 70 70 70 75 75 75 75 75 75 80 80 80 80 80 80 80 80 82 82 82 82 82 82 60 62 62 62 62 62 65 WIND mph 10 05 10 10 10 10 05 05 05 05 25 25 25 25 15 15 15 25 25 25 15 15 15 20 20 20 30 30 25 25 25 25 25 25 25 25 25 20 20 20 05 25 25 25 25 25 25 PERCENT SUN 100 100 100 100 100 100 100 100 100 100 90 90 90 90 90 90 90 90 90 90 90 90 90 100 100 100 95 95 100 100 100 100 100 100 80 80 80 60 60 60 100 95 100 100 100 100 95 NUMBER SWEEPS 300 300 300 300 300 300 300 300 300 300 200 200 200 200 200 200 200 200 200 200 300 300 300 300 300 300 300 300 300 300 300 300 300 300 n/r n/r n/r n/r n/r n/r n/r 300 300 300 300 300 300 83 A p p e n d ix SAMPLE IV (c o n t'd ) CULTIVAR DATE TIME OWNER (e s t ) 1971 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 (cont'd) Sunrise 20 May Sunrise 20 May Sunri se 20 May Midway 220 May Midway 220 May Redchief20 May Redchief20 May Redchief20 May Redchief20 May Redchief20 May Redchief20 May Midway2 20 May Midway2 20 May Sunri se 21 May M i d w a y 1 27 May M i d w a y 1 27 May M i d w a y 1 27 May Sun ri se 26 May Midway2 27 May Midway2 27 May Midway2 27 May Redchief27 May M i d w a y 1 27 May Sunri se 3 June M idwa y2 7 June Midway2 7 June Midway2 7 June Midway2 7 June Midway2 9 June Redchief9 June Midway! 9 June Wi Id 8 June Midway2 9 June Midway2 9 June Midway2 9 June Midway2 9 June Midway2 9 June Midway2 9 June Midwayl 9 June Paymaster 1OJun Vesper 10 Jun Midwayl 10 Jun Midwayl 10 Jun Midway2 10 Jun Midway2 10 Jun Redch ie f 10 Jun Sunri se 10 Jun 0200 0200 0200 0200 0200 0300 0300 0300 0300 0300 0300 0515 0515 0300 0230 0230 0230 n/r 0100 0115 0200 0200 0200 0300 0300 0310 0315 0320 0430 0445 0500 0300 0520 0530 0535 0545 0555 0605 0615 1015 1030 1040 1040 0130 0130 0145 0145 Pi ggott Pi ggott Pi ggott Pi ggott Pi ggott R a d e w a 1d RadewaId R ade wa1d RadewaId RadewaId RadewaId R a d e w a 1d RadewaId Hassel1 Lutz Lutz Lutz Hassel1 Lutz Lutz Lutz Lutz Lutz Lutz RadewaId R a d e w a 1d R a d e w a 1d R a d e w a 1d Lutz Lutz Lutz So Haven Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz TEMPERATURE WI NO °F mph 65 65 65 65 65 65 65 65 65 65 65 65 65 60 60 60 60 n/r 25 25 25 25 25 20 20 20 20 20 20 15 15 25 10 10 10 n/r 10 10 10 10 10 n/r 25 25 25 25 10 10 10 10 10 10 10 10 10 10 10 15 15 15 15 15 15 15 15 73 73 75 75 75 75 88 88 88 88 68 £Q wy 68 65 68 68 68 68 68 68 68 69 70 70 70 75 75 75 75 PERCENT SUN 95 95 95 95 95 95 95 95 95 95 95 100 100 95 100 100 100 n/r 90 90 95 95 95 n/r 80 80 80 80 100 100 100 0 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 NUMBE SWEEP 300 300 300 300 300 300 300 300 300 300 300 300 300 n/r n/r n/r n/r n/r n/r n/r 300 300 300 n/r 250 250 250 250 250 250 250 n/r 250 250 250 250 250 250 250 200 200 250 250 250 250 250 250 A p p e n d ix SAMPLE 1971 117 118 119 120 121 122 123 124 125 126 127 128 129 130 IV (c o n t'd ) CULTIVAR (cont'd) Midway 1 Midway 1 Surecrop Midway 2 M idway Midway 1 Midway 1 Midway 1 Midway 1 Midway 2 Midway 2 Mi dway 2 Midway 2 M idway 2 DATE 10 10 10 iO 10 10 10 10 10 10 10 10 10 10 Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun TIME (e s t ) 0200 0200 0215 0245 0245 0245 0300 0300 0315 0315 0320 0345 0345 0^00 OWNER Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Lutz Llltz TEMPERATURE °F 75 75 75 75 75 75 75 75 75 75 75 75 75 75 WI ND mph 15 15 15 15 15 15 15 15 15 15 15 15 15 15 PERCENT SUN 100 100 100 100 100 100 100 100 100 100 100 100 100 100 NUMBE SWEEF 250 250 250 250 250 250 250 250 250 250 250 250 250 250