q... .: a..‘.... "u“... .-.~-u»«.~.~.-.u-.~~q ......<_.W_M- v n In VYY—_V‘wan7x" - morons AFFECTING THE _-, GROWTH or HORSENETT-LE . 1 ' ‘ (SOLANUMCAROUNENSE‘LJ- __ 3,..- ‘ AND‘ITSRESPONSETQ‘. . .3 GLYPHOSATE-ANDTERWL; _ 3 Dissértatéon‘for :the Degree ofPh. D, ‘ 3 MICHIGAN STATELUNWERSITYX ? ‘ ' ‘ eaaco’m PAUL memo. : . .31974 t: LIBRARY Michigan State University - ‘v YW'W —.—— ‘— «— This is to certify that the . thesis entitled FACTORS AFFECTING THE GROWTH OF HORSENETTLE (SOLANUM CAROLINENSE L.) AND ITS RESPONSE TO GLYPHOSATE AND TERBACIL presented by Gregory Paul Pagano has been accepted towards fulfillment of the requirements for Ph . D . degree in Hort iculture M Major professor Datnggg 7. 19 24 0-7639 ulfliill‘ 800K mNDERYlNC. IIIIIIIIIIIIIIIIIIIIIIIIIIIII ABSTRACT FACTORS AFFECTING THE GROWTH OF HORSENETTLE (SOLANUM CAROLINENSE L.) AND ITS RESPONSE TO GLYPHOSATE AND TERBACIL. By Gregory Paul Pagano Horsenettle (Solanum carolinense L.) is a persistent perennial weed in many orchards, vineyards and cultivated fields in Michigan. The major problem in controlling this weed is the regrowth potential of the storage roots which can repeatedly produce new shoots as tops are removed. The objective of this study was to determine some factors which influence growth and reproduction of horsenettle and to de- fine parameters affecting the toxicity of a soil sterilant and translocated herbicide on this weed. High light and low night temperatures were found the most conducive to root formation and early flowering. Young plants (61 days from seed) were capable of producing new shoots from root sections within 28 days from sectioning. Plants with the root system left intact and the tops removed produced new shoots within l8 days. Horsenettle seed is susceptible to freezing. A tempera- ture of -l8.9 C for 40 days killed all seed. Seed from berries overwintered in the field had a 30% germination. Gregory Paul Pagano The starch content of the storage roots was about 36% prior to emergence in the spring, declined to l3% at flower- ing and increased by late summer to the original level. Horsenettle regrowth was controlled for the season with 2.2 kg/ha terbacil (3-tegt-butyl-5-chloro-6-methyluracil) in- dependent of the time of application in both a cultivated field and an orchard. Storage roots of plants receiving terbacil were almost completely depleted of starch by the end of the season. Glyphosate [N-(phosphonomethyl)glycine] provided effective control if applied at 4.5 kg/ha when the plants were in full flower. Glyphosate at 2.2 hg/ha applied during bloom did not control regrowth in the cultivated field. Gly- phosate applied at the prebud stage only slightly reduced starch levels in the storage roots at the end of the growing season, whereas applications at other times caused no apparent starch depletion. Both ‘4 C-labeled glyphosate and terbacil were applied to the leaves of horsenettle at four stages of growth. Labeled terbacil was also applied to the roots via nutrient solution. The ‘4 C-methyl labeled glyphosate was readily absorbed and translocated to meristematic regions. Glyphosate transloca- tion in older plants was over ten-fold that which occurred in younger plants although immature leaves of the younger plants initially absorbed more herbicide. Translocation of glyphosate follows a source to sink pattern typical of phloem transported chemicals. Gregory Paul Pagano Plants treated with 2-‘4c-terbacil were uniformly labeled after uptake from nutrient solution indicating xylem transport. Only 0.5 to l.0% of the applied terbacil was taken up by the leaves. There was limited translocation of 14C after foliar terbacil applications. FACTORS AFFECTING THE GROWTH OF HORSENETTLE (SOLANUM CAROLINENSE L.) AND ITS RESPONSE TO GLYPHOSATE AND TERBACIL By Gregory Paul Pagano A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Horticulture 1974 ACKNOWLEDGMENTS The author wishes to express his appreciation to Dr. Alan R. Putnam for both his friendship and guidance during the course of graduate study and in the prepara- tion of this thesis. Appreciation is also given to Drs. D. Penner, H. C. Price, S. K. Ries and M. J. Zabik for aid in the editing of this manuscript. Also acknowledged is the support and understanding given by my parents, Mr. and Mrs. E. V. Brennan. A special thanks also to Susan Smith for her help in the preparation of this thesis. ii TABLE OF CONTENTS ACKNOWLEDGMENTS . LIST OF TABLES LIST OF FIGURES INTRODUCTION . CHAPTER 1: LITERATURE REVIEW Horsenettle (Solanum carolinense L.) Distribution . Shoot morphology . Root morphology Economic Importance of Horsenettle The Vegetative Development and Reproduction of Horsenettle . . . . . . Development of Horsenettle from Seed Effect of Management Practices on the Control Herbicides for the Control of Horsenettle Control of Perennial Weeds with Glyphosate and Terbacil . . . . . . CHAPTER 2: SOME FACTORS AFFECTING VEGETATIVE GROWTH AND REPRODUCTION OF HORSENETTLE Abstract Introduction Materials and Methods Results and Discussion Page ii vi ahww Ch ll 12 I3 15 15 l6 17 18 Page Literature Cited . . . . . . . . . . . . . 22 CHAPTER 3: THE CONTROL OF HORSENETTLE WITH GLYPHOSATE AND TERBACIL AND THEIR EFFECT ON ROOT RESERVES . . . . . . . 23 Abstract . . . . . . . . . . . . . . . 23 Introduction . . . . . . . . . . . . . . 24 Materials and Methods . . . . . . . . . . . 25 Results and Discussion . . . . . . . . . . . 30 Literature Cited . . . . . . . . . . . . . 45 CHAPTER 4: THE UPTAKE AND MOVEMENT 0F 14c-LABELED GLYPHOSATE AND TERBACIL IN HORSENETTLE . . 47 Abstract . . . . . . . . . . . . . . . 47 Introduction . . . . . . . . . . . . . . 48 Materials and Methods . . . . . . . . . . . 49 Results and Discussion . . . . . . . . . . . 52 Literature Cited . . . . . . . . . . . . . 64 LIST OF REFERENCES . . . . . . . . . . . . . 65 APPENDICES . . . . . . . . . . . . . . . 70 iv LIST OF TABLES CHAPTER 2 l. Horsenettle growth as affected by light and temperature . 2. The development of new horsenettle plants from roots . . . 3. The germination of horsenettle seed from berries of various size and stages of ripeness following temperature treatments . CHAPTER 3 l. Descriptions of conditions for four herbicide applications on horsenettle in a pear orchard and a cultivated field 2. Control of horsenettle in a pear orchard with herbicides applied at several stages of growth 3. Control of horsenettle in a cultivated field with herbicide applied at several stages of growth . . . . . . . . . . 4. The effect of herbicides and herbicide combina- tions on the root starch reserves in horsenettle roots on August 23 CHAPTER 4 l. Uptake and translocation of 14C-glyphosate in horsenettle plants at four stages of growth 2. Uptake and translocation of ‘4C-terbacil by leaves of horsenettle at four stages of growth . 3. Uptake and translocation of 14C-terbacil in horse- nettle when applied in nutrient solution Page 19 20 21 27 3T 33 42 56 60 63 LIST OF FIGURES Page CHAPTER 3 1A. Effect of terbacil at 2.2 kg/ha on the starch reserve in horsenettle roots; a, control; b, applied May 23; c, applied June 12; d, applied June 20; applied July 5 . . . . . . 37 B. Effect of terbacil at 3.4 kg/ha on the starch reserve in horsenettle roots; a, control; b, applied May 23; c, applied June l2; d, applied June 20; e, applied July 5 . . . . . . 37 2A. Effect of glyphosate at 2.2 kg/ha on the starch reserve in horsenettle roots; a. control; b, applied June l2; c, applied June 20; d, applied July 5 . . . . . . . . . . . . . . 40 B. Effect of glyphosate at 4.5 kg/ha on the starch reserve in horsenettle roots; a, control; b, applied June 12; c, applied June 20; d, applied July 5 . . . . . . . . . . . . . . 40 CHAPTER 4 l. Translocation of 14C- -glyphosate and/or metabolites in horsenettle. The treated plant (left) and the corresponding radioautograph (right). A. Emergence B. Pre-Bud C. Early Flower 0. Late Flower . 53 2. Translocation of 14C-terbacil and/or metabolites in horsenettle. The treated plant (left) and the corresponding radioautograph, (right). A. Leaf treated 8. Roots treated 61 vi INTRODUCTION with the increase in the world population, the burden placed on agriculture to produce both food and fiber is one that must be carried well enough to insure an adequate supply of essentials. Anything that would impair the productivity of our farm lands must be controlled or abated. It has been estimated that in the United States weeds cause greater crop losses than either insects or plant diseases (l6). Weeds are the major barrier to food production and economic development in many regions of the world. Our abil- ity to control weeds which compete with crop plants for light (l8), water (52) and nutrients (29, 33) and thereby reduce all important cr0p yields may be a determining factor in the condition of the human health and well being for years to come. Needs are often grouped into three general classifications; perennial, annual and biennial. A perennial plant is one that lives at least 3 or more years. Simple perennials such as dandelion (Taraxacum officinale Weber), curly dock (Rumex crispus L.) and broadleaf plantain (Plantago major L.) repro- duce primarily by seed but can also reproduce vegetatively. Creeping perennials may reproduce by tubers, such as purple nutsedge (Cyperus rotundus L.), creeping roots as with field bindweed (Convolvulus arvensis L.), stolens as with bermuda- grass (Cynodon dactylon (L.) Pers.) or by rhizomes as in quackgrass (Agrogyron repens (L.) Beauv.) and spread rapidly through a field. They may also be introduced to another field by seed. Creeping perennials are probably the most difficult weeds to control, because of their extensive storage organs and capa- city for vegetative reproduction. Horsenettle (Solanum carolinense L.) is a member of this class of weeds. In Michigan it is often found in perennial crops such as orchards or asparagus grown on coarse textured soils. where perennial grass competition is minimal. Being a member of the Solanaceae, it is often found in fields where Solanaceous crops such as tomato (Lycopersicon esculentum Mill.) have been grown for a number of years and where herbicides were selective for horsenettle along with tomatoes. Horsenettle *3is also a host for several insects and diseases of solanaceous craps, compounding the problems it causes in the field. Herbi- cides and cultivation have not provided adequate horsenettle control in these crops. The results of some workers (l2, 23) indicated that cultivation actually enhanced the problem since the weed is capable of reproducing from small root sections. The purpose of this investigation was to study the fac- tors which affect the growth and reproduction of horsenettle and to determine if several new herbicides would provide ef- fective control. Factors affecting herbicide uptake and trans- location and effect on storage reserve depletion in the horse- nettle roots were also investigated. CHAPTER 1 LITERATURE REVIEW Horsenettle (Solanum carolinense L.) Distribution. Horsenettle (Solanum carolinense L.) is one of the numerous members of the nightshade family, Solanaceae. The plant is a perennial weed (l7) often found in waste places where grass competition is minimal (l2). Originally it was native to the southeastern states, but is not considered a troublesome weed there (l, 19). Currently, it is established as a weed as far north as Vermont, Pennsylvania. Ontario, Michigan and Minnesota and west to Washington and California (11, 17, 19, 27). Shoot morphology. Horsenettle is an erect stemmed and branched plant up to l m. The main stem, branches, petioles, calyx, mid- ribs and lateral veins of leaves have rigid, sharply pointed, yellowish spines and four to eight rayed hairs. The leaves are alternate, simple, 5 to 9 cm long, oblong to ovate in outline with unevenly lobed, toothed or deeply cut margins (23). The flowers, on spiny petioles are perfect, complete and open indeterminant racemes. The spiny peduncles are irregular- ly spaced along the sides of the stems. The five lobed carol- la varies in color from violet to white and is about 2.5 cm in diameter. It closely resembles the flower of the common potato (Solanum tuberosum L.). There are five fused yellow stamens surrounding the two-celled ovary (17). The fruit or berry is tomato-like, smooth, round, one to two cm in diameter, orange yellow in color when mature and subtended but not enclosed by the calyx (l7). The seeds of horsenettle resemble those of the common potato in size, shape, color, and internal structure (23). It is yellow brown in color, orbicular in outline and flat- tened in cross section. The surface has a slightly pebbled appearance. Root morphology. Horsenettle is considered to have a taproot and creeping rootstock system (49). The roots range in color from light brown to almost white. They are thick and some- what fleshy. The lack of agreement in the literature on whether horsenettle is spread by means of rhizomes or creep- ing horizontal roots or rootstocks (3, 25, 3l, 49) prompted llnicki gt 11. (23) to investigate the nature of the tissue. Using phloroglucinal stain which is specific for lignins it was determined that in no instance did an underground part of the plant produce the characteristic staining which would have classified it as a stem like structure. llnicki con- cluded that all underground portions are roots and not shoots. Economic importance of horsenettle. Horsenettle along with other weeds compete for water, nutrients, light and space with crop species. This alone would be reason enough to at— tempt total eradication of the weed. Perennial weeds are particularly competitive and cause not only yield reductions, but may also reduce the stand of perennial crops like asparagus. Horsenettle has been shown to be an important host for the potato psyllid (Protrioza cockerelli Sulc.) which trans— mits psyllid yellows disease to the potato and tomato (51). Other important crop insects reported to be harbored by horse- nettle are the potato flea beetles (Epitrix fuscula Crotch) (14), Colorado potato beetle (Leptinotarsa decemlineata Say) (29), potato stalk borer (Trichobares thinotata Say) (23), onion thrips (Thrips tobaci Lind.) (23), and the greenhouse redspider mite (Tetranychus telaruis L.) (31). Horsenettle is also a host for the fungi (Septoria lycoper- sigl Speg.) which causes a leafspot in tomato (36), the disease organism (Verticillium albo-atrum Reinke and Berth) which causes Verticillium wilt of tomato (23), and to the mosaic virus which causes potato and tomato mosaic (31). Need control methods requiring considerable hand labor or fuel may represent a large portion of the input required to produce a crop. This input is reflected in higher food costs (26). Horsenettle, a perennial without any acceptable long time chemical means of control, is often spot treated with a contact herbicide or repeatedly cultivated. This adds to the time requirement and the cost of production. Horse- nettle presents another problem when present in crops such as asparagus and tomatoes where hand harvesting is a common practice. The spines present on the leaves and stems make hand picking of the crops slow and difficult and labor may actually refuse to enter the field. Heavily infested fields may actually have to be taken out of crop production causing great economic loss. Horsenettle berries have been reported as being poison- ous (32) and when present in forage, they have caused losses in cattle and horses (27). The vegetative development and reproduction of horsenettle. Bradbury (12) observed differences in growth patterns between disturbed and undisturbed infestations of the weed. The older undisturbed areas were less thickly populated with horsenettle than were cultivated areas. Thicker stands on cropland were attributed to propagation from pieces of root stalks mixed in the soil by seedbed preparation and other cultural practices. Kiltz (25) showed that the roots grow to depths of 2.4 m in heavy soils and that creeping roots found in the upper 45 cm of soil extended 0.9 to 1.2 m from the main root. Bradbury's (12) excavation of horsenettle revealed a penetration of at least 2 m in depth. He excavated a single intact creeping root 5.8 m in length having numerous shoots emerging from it. Most of the work completed on the reproduction of horse- nettle was done as a joint effort of the New Jersey Agricultural Experiment Station and New York Agricultural Experiment Sta- tion under llnicki and Fertig respectively (23). Working with seedlings, it was found that the maximum increase in plant height occurred during the middle of the growing season (August) whereas the maximum increase in root length occurred during the latter part of the season (September). Plants started from seed become firmly established early in the growth period due to rapid and extensive root development which occurred at the expense of foliage growth. They con- cluded seedling control is necessary to prevent firm establish- ment of plants from seed. A study on the influence of size of root cutting on re- production showed that cuttings over 2.5 cm in length and 1 cm in diameter would produce new plants within 42 days. Thus cultivation could play an important role in the dessimation of the weed by root cuttings. Bradbury (12) reported that older. undisturbed areas were less thickly populated, most likely be- cause of the roots being contiguous and poor reproduction by seed. In another test, several plants which had been grown for one year from seed in wooden flats were dug up and the roots cut into sections 15 cm in length. These were planted out- doors at depths of 7.5, 15, 30 and 45 cm. All cuttings pro- duced at least one shoot each from depths down to 30 cm. Four out of six cuttings produced plants from the 45 cm depth 67 days after planting. Based on this observation the authors did not expect an appreciable reduction in stand from deep tillage that is normally practiced in the Northeast. They speculated that fallowing may gradually reduce the stand by depletion of the root reserve. The effect of polarity on asexual reproduction from horsenettle roots has also been studied. Segments were taken from the vertical taproot developed shoots at the morphological apex in approximately 80% of the cases. The lateral root sections produced very few shoots. Explanations offered for this phenomenon include a con- centration differential of nutrients or other growth factors from one end of these segments to the other end. However, it was also shown that the lower portions of the taproot are higher in starch than the upper portion suggesting that a slight starch differential exists in the taproot section. The morphological apex being somewhat lower in starch content than the other end could affect a relative increase in the amount of protein available for new shoot growth. Apparently, segments are capable of producing shoots from the morphological apex regardless of the planting position or size of the cutting. Furthermore, the distance removed from the top of the vertical taproot did not affect the production of the shoots. The findings have both practical and fundamental appli- cations. A growth controlling mechanism exists and if deter- mined, could give greater insight to the nature of regrowth of perennial weeds. Furthermore, practical control of horsenettle might be achieved by adjusting conditions to take advantage of this growth controlling mechanism either by stimulating shoot growth in an attempt of systematically exhaust the reserves in the root or total suppression of shoot growth. Development of Horsenettle from Seed. llnicki and Fertig (23) also performed a number of tests on seed germination and seed- ling growth. There was considerable variation in the number of seeds per berry. They found that numbers of seeds varied from 161 for large berries to 13 for small berries. The average number of seeds for all berries was 86. In a study to determine the effect of light on seed germi- nation it was found that light was not an important factor af- fecting total germination, but that exposure to light increased the germination rate. Pre-germination cold treatments had no effect on germina- tion. The condition most favorable to germination of mature seed overwintered in the field was alternating the tempera- tures from 20 to 30 C in the dark and moistening the seed with a 0.2 percent potassium nitrate solution. Bradbury (17) indicated that emergence of horsenettle plants from seed under field conditions was a rare occurrence. llnicki (23) studied the dissemation of seed under natural conditions. On May 15th about .04 ha of a 1.6 ha field near 10 Newfield, New York was surveyed. Fifteen seedling locations were found and marked for future observations. About 200 seedlings were found in this area. Observations in September, 1959, showed that 50 percent of the seedlings had survived the summer. No data was reported on the number of seedlings that survived the winter, although the author concluded that emergence form seed was an important factor to be considered in the dissemination of the weed. It is important to note however, that this work was conducted on non crop land (ie. land that received no tillage or herbicide applications). Tests were conducted to determine the effects of soil type on the germination of horsenettle seed planted at various depths (23). The most rapid rate of emergence was at the 2.5 cm depth and occurred during the first 3 weeks after planting. Seed planted at the 7.5 cm depth showed practically no emergence until 4 weeks after planting. Emergence of seedlings from the 2.5 cm depth was four to ten times greater than from the 7.5 cm depth in the well drained soils. Percent emergence in the fine textured soils was less than one half that in the well drained soils at the 2.5 cm depth. No seedlings emerged from the 7.5 cm depth in the fine textured soils. It appears that the chances of horsenettle infestations starting from seed are consider- able greater on coarse textured well drained soils than on heavy, somewhat poorly drained soils. Reports indicate that seedlings can emerge from mature, undried whole berries located within 2.5 cm of the soil sur- face. Seedlings emerged more rapidly from broken berries than 11 from unbroken ones (23). The emergence from berries may in- dicate why the horsenettle seedlings found growing in the field described earlier were generally found to be clustered with about 15 to 20 seedlings at a location. The effect of over-wintering on young horsenettle seed- lings has been studied. On August 9, 120 seeds were placed in frames at a depth of 2 cm. Sixty eight percent emergence was obtained within 37 days. Of the 82 plants produced from seed, eight plants (10%) survived the winter. Control of Horsenettle Effect of management practices on control. llnicki (23) studied the influence of the stage of seedling development on regrowth after top removal. Top growth was cut from seedlings at the soil surface at intervals of 15 to 30 days after emergence of the seedling. Regrowth was produced when shoots were removed even early in the seedling stage. With increased age of horsenettle plants, more rapid regrowth of shoots occurred fol- lowing temporary setbacks due to tap removal. llnicki gt 31. (2) also studied the effect of cutting frequency on subsequent growth. A cutting height of 6.3 cm was used to approximate the height of cut of the conventional farm mowing equipment. After planting root cuttings on April 28, shoots began emerging by May 30 and of the 92 root cuttings. 91 produced at least one shoot. All plants receiving the cut- ting treatment at 6.3 cm every 5 to 8 days survived the treat- 12 ment. These plants over-wintered with no mortality and were growing vigorously in the following spring. Two of the 12 plants receiving this treatment produced berries below the cutting height. These plants, subjected to a vigorous cutting schedule produced a relatively large number of leaves due to the greatly shortened internodes on the main stem. This com- pact, rosette-type appearance was a characteristic change in the habit of growth. The large leaf area provided sufficient photosythetic surface to maintain a daily growth rate compar- able to plants cut at less frequent intervals. Plants cut more than once during the season maintained a greater daily growth rate than those cut at less frequent intervals or not at all possibly because they remained in the actively growing vegetative stage for a longer period of time. In plants that were alowered to flower and seed, the growth rate declined sharply. The data indicated that frequent clip- ping is not a reliable method of reducing a horsenettle in- festation. Herbicides for the control of horsenettle. Neville (34) studied horsenettle control in corn and obtained moderate control with 2.2 and 3.4 kg/ha of 2,4-D (2,4-dichlorophenoxy- acetic acid) and a 2.4-0 plus 2,4,5-T (2,4,5-trichlor0phenoxy- acetic acid) mixture produced moderate injury to the plant. Bradbury (12) in New Jersey reported a 100 percent reduction in a horsenettle stand with a fall application of 35.8 kg/ha 13 of 2.4-0. He also found that 4.5 kg/ha of amitrole (3-amino- 1,2,4-triazole) applied during flowering produced good control. It was shown that a mixture of 2.4-0 and 2,4,5-T was more ef- fective than either chemical used alone. Hemphill (20) in Missouri obtained control of horsenettle with amitrole at 2.2 kg/ha applied to the foliage in August. Fair control was obtained with 2,3,6-TBA (2,3,6-trichlorobenzoic acid) at 3.4 kg/ha per acre. Control of perennial weeds with glyphosate [N-(phosphonomethyl) glycine] and terbacil (3-tert-butyl-5-chloro-6-methyluracil). Glyphosate, introduced in 1971, was shown by numerous workers to have a wide range of activity on both annual and perennial weeds. Tweedy et 11. (48) reported effective yellow nutsedge (Cyperus esculentus L.) and purple nutsedge (Cyperus rotundus L.) control in the greenhouse at 2.2 kg/ha when applied when the plants were at the 3rd, 6th, 9th, and 12th leaf stage. Stoller (47) also reported good yellow nutsedge control with 2.2 kg/ha glyphosate. His ratings, taken 4 weeks after appli- cation, indicated that younger plants were more susceptible to glyphosate than older more established plants. Arnold (4) reported that a single fall application of glyphosate was more effective than spring applications for Canada thistle [Cirsium arvense (L.) Scop.], however, a fall application at 2.2 kg/ha following by 1.1 kg/ha in the spring was the best treatment. Messersmith (30) also reported good Canada thistle and field bindweed (Convolvulus arvensis L.) 14 control with a single 2.2 kg/ha application of glyphosate in the fall. Jorgenson (24) reported that glyphosate at 1.1 and 2.4 kg/ha applied twice in the fall showed good field bindweed control the following year. Glyphosate has given excellent control of the perennial grasses, quackgrass [Agropyron repens (L.) Beauv.] (44) and johnsongrass [Sorghum halepense (L.) Pers.] (46). Rates of 1.1 to 3.4 kg/ha gave effective control of quackgrass the season after treatment (6, 7, 10, 45). Herbicide efficiency also appeared to be related to the stage of growth of the quackgrass. Older plants appear to be more susceptible than younger ones (6, 13, 50). Terbacil at rates of 0.5 to 3.5 kg/ha gave good annual weed control whereas rates up to 8.5 kg/ha provided effective control of bermudagrass [Cynodon dactylon (L.) Pers.], quack- grass, horsenettle and red sorrel (Rumex acetosella L.) (5, 38, 39, 40). In the papers reviewed, the time of applica- tion did not appear to be a factor in control. This may be related to the fact that uracils are less firmly absorbed by soils than many herbicides and will move into the deeper soil horizons following rain (42). CHAPTER 2 SOME FACTORS AFFECTING VEGETATIVE GROWTH AND REPRODUCTION OF HORSENETTLE. ABSTRACT Horsenettle (Solanum carolinense L.) is a persistent perennial weed found in many areas of Michigan. High light and low night temperatures were found the most conducive to root formation and early flowering. Young plants (61 days from seed) were capable of producing new shoots from root sections within 28 days from sectioning. Plants with the root system left intact and the tops removed produced new shoots within 18 days. Horsenettle seed is susceptible to freezing. A temperature of -18.9 C for 40 days killed all seed. Seed from berries overwintered in the field had a 30% germination. 15 16 INTRODUCTION The ability of horsenettle (Solanum carolinense L.) to produce new plants from intact or cut sections of roots is the major factor in the spread of this perennial weed. Nhen' undisturbed, horsenettle produces a formidable storage root system seemingly out of proportion to its limited shoot growth. Little is known about the influence environmental factors have on the production of shoots, flowers and roots. If shoot and flower production is at the expense of root growth, the mani- pulation of the plant to decrease storage root production would aid control of this perennial weed. Experiments conducted in the northeast demonstrated the high reproductive capacity of horsenettle roots (2). Repro- duction from seed was also considered to occur on non-crop areas. The objective of this study was to determine the effects of light intensity and temperature on production of shoot and root growth and to ascertain the reproduction capabilities of Michigan clones by root cuttings and seed. 17 MATERIALS AND METHODS Effect of Light Intensity and Temperature on Shoot and Root Growth. Root sections were collected from a field in central Michigan, cut into segments 2 cm in length and planted in a soil peat moss mixture (4:1, vzv). After emergence they were taken out of the greenhouse and placed in growth chambers. One chamber was maintained with a night temperature of 23.8 C and the other 15.5 C. Both had a day temperature of 32.2 C (14 hours). Light intensity was regulated by varying the dis- tance the plants were from the light source. The two light intensities studied were 17.8 and 6.5 klux. Flower counts were made 30 days after treatments were imposed. Forty-five days after the plants were first placed in the growth chamber they were harvested, separated into shoot and roots, dryed (47 C) and weighed. Reproductive Capability from Root Sections. Twenty-five day old seedlings were planted in 10 cm pots and allowed to grow for 5 or 7 weeks. After initial growth the roots were measured and sectioned into four equal sections: based on morphological position; ie. nearest the root apex or nearest the crown. In another test only the shoot was removed and the root left intact. The root sections were incubated in a growth chamber with a 14 hour day (17.2 klux) with a day temperature of 30.0 C 18 and a night temperature of 18 C. The growth medium was horti- cultural vermiculite and a half strength Hoagland's solution (pH 6.3) (l) was supplied as needed. Germination Capability of Frozen and Refrigerated Seed. Horse- nettle berries were harvested on October 27 from a field in central Michigan. They were separated into nine categories, based on berry size and ripeness. They were then split into two groups. Half of the berries were frozen at -18.9 C and the rest were refrigerated at 2.8 C for forty days. After the cold treatment the berries were split on one side and seeds were placed on filter paper and dryed for 24 hours at 33 C. Ten seeds from each treatment were then placed on filter paper in petri dishes to which 8 ml of distilled water was added. The seeds were incubated in the dark at 29 C for 8 days. In another test berries were collected on March 15 at a field in southwestern Michigan and were dryed and incubated as before to determine the viability of seed after exposure to a Michigan winter. RESULTS AND DISCUSSIONS Effect of Light Intensity and Temperature on Shoot and Root Growth. Plants growing under the higher light intensity flower- ed earlier than those grown with lower light (Table l). The combination of high light and low night temperature had the 19 earliest flowers. In a later experiment it was noted that Table 1.--Horsenettle growth as affected by light intensity and temperature. 3/ Light intensity 17.8 klux 6.5 klux Temperature ( C) Flowers/ Root/ Flowers/ Root/ Day Night Plant Shoot Plant Shoot 32.2 15.5 5.3 0.52 0.9 0.36 32.2 23.8 1.4 0.41 0.4 0.38 9, Each observation is the average for nine plants. horsenettle growing in an open field flowered earlier than that under the canopy of trees in an orchard. The delay in flower- ing maybe related to light intensity as demonstrated in the growth chambers. Higher light and low night temperatures also produced the highest root:shoot ratio. Apparently, with the higher light more carbohydrates are produced and in turn, less is respired if the night temperature is low. This could provide more storage root as opposed to production of foliage. Reproduction Capability from Root Sections and Intact Roots. The time required of horsenettle to obtain the perennial habit was less than 61 days from seed (Table 2). Although root sections at the morphological apex of the root did not have the same regrowth potential as sections from the other 20 Table 2.--The development of new horsenettle plants from roots. Days from Days to new shoots a/ Days to new shoots seed from root sections — from intact roots 1 2 3 4 61 28.09/ 20.8 20.5 19.3 17.3 75 24.3 19.5 20.0 27.8 17.5 Ell-section nearest the root apex 4-section nearest the plant crown 2 and 3 intermediary. E/50% regrowth all others had 100% regrowth. parts of the root, the perennial habit of the plant even at early stages of growth is evident since over all 95% of the root sections produced shoots. When only the shoot was re- moved and the root left intact, new shoots were visible with- in 18 days. It is evident from this data that control of horsenettle seedlings is important to prevent introductions to a non- infested field. Disking of horsenettle would encourage spread of the weed problem and not be an effective means of control. The use of a contact, non-translocated herbicide would apparent- ly give little season long control. Germination Capability of Frozen and Refrigerated Seed. The exposure of the berries to -18.9 C killed all the seed. With the refrigerated seed the germination percent over all berry sizes and stages averaged 22.8% with extremely variable results (Table 3). 21 Table 3.--The germination of horsenettle seed from berries of various size and stages of ripeness following tem- perature treatments. %Germination Stage Berry Diameter (cm) 2.8 C -18.9 C Green 1.7 30.0 0.0 Green 1.3 36.7 0.0 Green 0.8 46.7 0.0 Yellow 1.7 23.6 0.0 Yellow 1.4 23.6 0.0 Yellow 1.2 10.0 0.0 Ripe 1.7 33.6 0.0 Ripe 1.4 0.0 0.0 Ripe 0.8 3.0 0.0 Average 22.8 0.0 Seed from unripe berries had the highest percent germina- tion (37.8%). The berries overwintered in the field had a 30.0% germination. The data indicates that germination of seed is variable and that extreme prolonged freezing would kill the seed. In Michigan horsenettle seedlings are rarely seen. The most likely location for infestations by seed would appear to be fields where Solanceous crops are produced and herbi- cides used are selective for horsenettle along with the weed. In fields where effective pre-emergence herbicides are used and non-Solanaceous crops are planted, infestation from seed would not be likely to occur. 22 Literature Cited 1. Hoagland, D. R. and D. I. Arnon. 1938. The water culture method for growing plants without soil. Univ. Calif. Agri. Exp. Sta. Circ. 347. 2. llnicki, R. 0., T. F. Tisdell, S. N. Fertig and A. S. Furrer. 1962. Life history studies as related to weed control in the northeast. III-Horsenettle. North East Regional Pub. Bul. 368. CHAPTER 3 THE CONTROL OF HORSENETTLE WITH GLYPHOSATE AND TERBACIL AND THEIR EFFECT ON ROOT RESERVES ABSTRACT Horsenettle (Solanum carolinense L.) regrowth was con- trolled with 2.2 kg/ha terbacil (3-tegt-butyl-5-chloro-6-methy1- uracil) in both a cultivated field and an orchard situation independent of the time of application. Glyphosate [N-(phos- phonomethyl)glycine] provided effective control if applied at 4.5 kg/ha when the plants were in full flower. Glyphosate at 2.2 kg/ha applied during bloom did not control regrowth in the cultivated field. All terbacil treatments in the cultivated field caused 82-98% reductions in starch content in the roots late in the season. Glyphosate applied prior to flowering only slightly reduced starch levels in storage roots at the end of the growing season whereas the other glyphosate treat- ments did not reduce the starch content in the remaining viable roots. 23 24 INTRODUCTION Horsenettle (Solanum carolinense L.) has become a persis- tant perennial weed in many orchards and cultivated fields in Michigan. The use of rmrbfifides which control annual weeds and quackgrass [Agropyron repens (L.) Beauv.] has reduced com- petition and are believed to have favored the spread of peren- nial weeds in many fields. The substituted uracil, terbacil (3-tgtt-butyl-5-chloro- 6-methy1uracil) controls a wide range of both perennial and annual weeds (12, 13). The uptake of terbacil is primarily through plant roots and movement is apoplastic in the xylem. It is relatively soluble in water (710 ppm) and hence will leach into the deeper soil horizons when irrigated or moisten- ed by rainfall (11, 14). Its mobility in soil may be advan- tageous in controlling deep rooted perennials. Glyphosate [N-(phosphonomethyl)glycine] has been reported to be a non-selective translocated herbicide which controls perennial weeds (2, 4, 9). Numerous workers reported that time of application was an important factor in the control achieved with glyphosate (2,-3, 5, 9). Often the concept of "root or storage reserve" (10) is mentioned as the determinant factor in eradication of creep- ing perennial weeds. llnicki gt gt. (7) analyzed horsenettle roots for starch content as an estimate of this food reserve and found that root starch levels fluctuated from 34% at 25 emergence to 13% at flower in the upper 25 cm of root whereas the lower 25 cm of roots remained at about 40% throughout the growing season. Starch estimations are justified since an available carbohydrate source is necessary in the spring for early growth and tissue production when carbohydrate demand exceeds photosynthetic capability (l, 15). The purpose of this investigation was to determine the optimum time to apply either glyphosate or terbacilfor horse- nettle control in an orchard and a cultivated field, and if these herbicides would effectively deplete the starch reserve of storage roots. MATERIALS AND METHODS Herbicide application. Preliminary experiments to select the most effective herbicides for the control of horsenettle were conducted in a cherry orchard in northwestern Michigan and in an asparagus field in southwestern Michigan in 1972.. Since glyphosate and terbacil were the most effective herbicides in these experiments, tests were set up in 1973 to determine the optimum time of application for these herbicides. Two locations in southwestern Michigan were chosen as test sites because of their severe and relatively uniform infesta- tions. One was a young pear orchard where grass was not a serious weed problem under the trees and horsenettle was the predominant perennial weed. This orchard was maintained with sod strips between the rows of trees, a common practice in 26 Michigan orchards. Treatments were applied four times during the season. The time of application was based on the morpholo- gical stage of the horsenettle, i.e., emergence, full leaf, bloom and late bloom. The other location was a field which had been planted to tomatoes for several years. Horsenettle was the predominant weed in the area since the herbicides and cultivation practices used for tomato production had encouraged its development. Pertinent data regarding application at both locations are pre- sented in Table l. The treatments at both locations were applied in volumes equivalent to 337 L/ha, with a plot size of 3.7 by 7.6 m in the cultivated field and 2.4 by 7.6 m in the orchard. The ex- perimental design was a randomized complete block with three replications. The date of application at both locations did not coincide since the horsenettle in the orchard emerged and flowered later than that in the cultivated field. The 80% wettable powder formulation of terbacil and the 0.35 kg/L formulation containing the isopropylamine salt of glyphosate were applied with a small plot sprayer using carbon dioxide as a pressure source. Need control ratings were based on a l to 9 scale with 1 representing no injury and 9 indicating complete foliage kill. A rating of 6.5 indicated commercially acceptable horsenettle control. All data were subjected to analysis of variance and means were compared using Tukey's H.S.D test. 27 ll. .1. .l. 4.4 Asev mesa; am eeeeez eeem mm mm Fm e, Auv eeaeaeeaeee _.em mm em om 4_ Age eeeeeeeQEee EF< me-mm mm-om o~-o_ m-o AEUV Semeee peepa soaps one; soopm camp ppzm mocmmcoEm cuzogm eo mmepm mN »_=e m »_=q NP eeeo mm an: meme eeeeeeepae< Emo~ xucmm . Pwom ucmgoco Lama .l. e.. ll. m.o Aeev mesa; em e_ee.z apex on em Pm m. Auv eeeeaeeaeee Peem _m on on a, flue eeeeaeeaeee ee< m.-oe oe-mm mm-o~ m-o Asev peace; Seepa Eco—n mum; sooyn xpcmw mmoF Ppam mocomcmsm spzocm mo ommum ON span ON mesa ~_ mesa mN an: meme eeeeee._ea< ucmm xswop . F_om e_e.c eeea>_e_=u a u m < capeaeeemeo ee.m :o_umowpqa< .upope woum>pupzo a van neoguco game a cw mpuuocomco; co meowumoWFaam ou_ovagos Lao» Lee meowawucoo mo :oquwgumonll.p open» 28 Root collection and preparation for analysis. Seven times throughout the season, storage roots were collected in the cultivated field for starch analysis. Roots used for analysis were only those which had shoots growing from them, (i.e. viable roots in the upper 30 cm of the soil). Shoots arising from the roots were discarded and only fleshy storage roots were placed in plastic bags in ice for transport to the labora- tory. Roots were kept frozen until they were prepared for lypho- lyzation. Frozen roots were cut into 2 cm sections and washed under distilled water to remove any soil. After being placed in a covered Petri dish and covered with crushed dry ice for 45 minutes, the roots were then freeze-dried for 24 hours. The dried roots were then ground through both a 20 and 60 mesh screen with a Wiley Mill. The powder was collected in plastic vials with tight caps and stored frozen until starch levels were determined. Starch Analysis. The procedure was similar to that of McCready gt gt. (8) and Yemm and Willis (16) with the following modifi- cations: To remove any sugars which would react with the anthrone reagent used for starch determinations an ethanol cleaning procedure was utilized. Into a round bottom plastic centri- fuge tube, 20 ml of 80% ethanol was added to 50 mg of ground root tissue, stirred, and placed into a hot water bath (70 C) for 10 minutes. The samples were then centrifuged at 1290 g 29 for 10 minutes, after which the supernatant was discarded. This was repeated a total of three times. To the residue 5 ml of water and then 6.5 ml of 52% perchloric acid was added. Samples were stirred for 10 minutes and 5.0 m1 of water added to the tubes prior to centrifugation for 10 minutes at 1290 g. The supernatant was transferred to a 50 m1 test tube and the residue retreated as before with 5 ml water and 6.5 ml 52% perchloric acid and stirred. After 5 minutes, 5 ml water was again added, the sample was shaken, and quickly poured into the graduated test tube through a suction apparatus equipped with Buchner funnel and Hhatman no. 1 filter paper. The sam- ples were brought up to a volume of 50 ml with distilled water prior to the anthrone test. 1 The anthrone solution (0.2 anthrone per 100 ml 75% H2504) was prepared daily. One tenth of the solublized starch solu- tion was placed in a test tube. Ten m1 of the anthrone solu- tion was then added and the tube shaken vigorously for 15 seconds. The tubes were placed in a boiling water bath for 7.5 minutes and placed in an ice bath to stop the reaction. Absorbance at 620 nm was determined with a Beckman Grating Spectrophotometer Model 08-6. A conversion factor of 0.92 was used to convert the solublized starch levels to starch. The glucose standard was made fresh daily. Starch levels are expressed as milligrams per gram dry weight. All starch data were subject to analysis of varience and means were compared to control using Tukey's H.S.D. test. 30 RESULTS AND DISCUSSION Horsenettle control in the orchard. At the earliest applica- tion date, May 23, only terbacil was applied to the plots since few horsenettle shoots had emerged and glyphosate was believed to have no soil activity. Terbacil provided excellent control of horsenettle 90 days after a single application of 3.4 kg/ha at the time shoots were just emerging through the soil (Table 2). It appeared that terbacil was absorbed by the roots of horse- nettle, and either prevented the formation of new shoots or killed them soon after they were formed. By June 12 the horsenettle was 10 to 20 cm high and in full leaf, however, no flowers or flower buds were apparent on the plants. Terbacil applied at that time gave excellent control for 75 days after a single application of 3.4 kg/ha or when combined with glyphosate at 2.2 plus 2.2 kg/ha or with paraquat at 2.2 plus 1.1 kg/ha.. Glyphosate applied alone on this date at 4.5 kg/ha did not give acceptable season—long control al- though it initially burned off the foliage. Apparently this herbicide was not translocated to the roots in sufficient quantity to control regrowth from the roots. At the third treatment date, July 5, the horsenettle in the orchard was 20 to 35 cm high and in full bloom. Glyphosate at 4.5 kg/ha applied on this date gave excellent control of horsenettle 45 days after the single application. As with the earlier treatments, terbacil when applied either alone or in 31 Table 2.--Control ratings on horsenettle in a pear orchard with herbi- cides applied at several stages of growth. 2] fii Stage of growth 9! Herbicide Rate A 3 c D 9/ (kg/ha) None -— 1.0 1.0 1.0 1.0 Terbacil 3.4 7.7 8.0 8.0 6.7 Glyphosate 4.5 -——- 3.0 8.3 2.7 Glyphosate + Terbacil 2.2+2.2 -——— 7.3 8.7 8.7 Terbacil + Paraquat 2.2+l.l ———- 8.7 8.7 8.7 H.S.D. 5% ' 1.0 1.5 2.4 E/Ratlng date: August 25. 9/Rating system where 1 = no control and 9 = complete regrowth inhibition. s/Time of application for A was May 23 (emergence); B was June 12 (full leaf); C was July 5 (bloom) and D was July 25 (late bloom). 32 combination with the other herbicides gave excellent control. The effectiveness of the glyphosate applied at bloom indicates that the herbicide was translocated, most likely symplastical- ly to the roots and accumulated at a high enough concentration to give control of newly emerging shoots. The latest applications were made when the horsenettle was in late bloom stage and the plants were 35 to 45 cm high. Again, terbacil applied either alone or in combination with the other herbicides gave good control of horsenettle. Glyphosate applied on this date failed to give the desired control, per- haps because the herbicide wasn't translocated to the roots as occurred with glyphosate applications on June 12. It was apparent that to control horsenettle in the Orchard with gly- phosate, the time of application was of extreme importance. With the soil sterilant, terbacil, control was independent of the time of application. Horsenettle control in a cultivated field. In contrast to the previous experiment in the orchard, glyphosate was applied at 2.2 and 4.5 kg/ha and terbacil at 2.2 and 3.4 kg/ha. Paraquat was included at the 1.1 kg/ha rate and in combination with terbacil at 3.4 plus 1.1 kg/ha paraquat. At the earliest application date in the field (Table 3) only terbacil was applied. A single application of terbacil at either 2.2 or 3.4 kg/ha gave excellent horsenettle control 105 days after treatment. 33 Table 3.--Control ratings on horsenettle in a cultivated field with herbi- cides applied at several stages of growth.9/ Stage of growth 9/ Herbicide Rate A B c o 3’ (ks/ha) None -—- 1.0 1.0 1.0 1.0 Terbacil 2.2 8.0 7.3 7.7 7.0 Terbacil 3.4 8.0 8.0 8.0 6.6 Glyphosate 2.2 ———- 3.3 3.3 3.0 Glyphosate 4.5 -——- 2.3 1.3 7.3 Glyphosate + Terbacil 2.2+2.2 -——- 8.0 7.3 7.3 ‘ Paraquat _ 1.1 —— 13.3 1.0 1.0 Terbacil + Paraquat 3.4+l.l -——- g. .7 8.0 7.0 H.S.D 5% 3 1.3 1.2 1.3 3/Rating date: September 6 QIRating system where 1 = no control and 9 = complete regrowth inhibition. 2/Time of application for A was May 23 (emergence); B was June 12 (full leaf); C was June 20 (early bloom) and D was July 5 (late bloom). p.‘ 34 By June 12, the horsenettle was 20 to 35 cm high, with fully expanded leaves but no flowers or flower buds were present. Terbacil applied at either rate or in combination with the other herbicides tested gave excellent control 85 days after the single herbicide application. Glyphosate applied at this time at either 2.2 or 4.5 kg/ha gave only short term control, as did paraquat when used alone. On the third treatment date, June 20, the horsenettle was 35 to 60 cm high and in the early bloom stage. Terbacil at either 2.2 or 3.4 kg/ha or in combination with either glyphosate or paraquat gave excellent control of horsenettle 77 days after the single application of the herbicides. Glyphosate at either 2.2 or 4.5 kg/ha did not provide effective season-long control although it was somewhat better than paraquat. On July 5, the horsenettle was 60 to 75 cm high and in the late bloom stage. Terbacil at either 2.2 or 3.4 kg/ha gave good control when applied either alone or in combination with the other herbicides tested. Glyphosate, at 4.5 kg/ha provided good control 62 days after application while 2.2 kg/ha was not adequate. Paraquat at 1.1 kg/ha was identical to the check non-treated plot. It is evident that season long control of horsenettle is possible with a single application of terbacil at 2.2 kg/ha regardless of the time of application. To achieve Optimum con- trol with glyphosate, however, the time of application was of paramount importance. Horsenettle was most susceptible to glyphosate when in the flowering stage. This may be related 35 to the carbohydrate reserve in the roots being at a seasonal low, hindering the ability of the plant to regenerate shoots from below ground portions. It may also be related to the amount and primary direction of translocation of sugars dur- ing this period. During flowering, sugars may be translocated from leaves or storage roots to active sinks in meristematic areas. The effect ofglyphosate and terbacil on root starch reserves. The early reduction of starch reserves in the roots indicates hydrolysis and utilization during the initial plant growth phase whereas starch accumulates during subsequent plant de- velopment (Figure 1A). With an increase in shoot growth the first 3 weeks after emergence the reserves dropped from 360 mg/g to 140 mg/g. Afterward there was a gradual rise in root starch levels even as the plants were going through flower and fruit set reaching 353 mg/9 by late August. The plant had in effect completed the cycle or reserve depletion caused by early growth and refurnished the starch during the subsequent 10 weeks. Terbacil at 2.2 kg/ha applied on either May 23, June 12, June 30, or July 5 reduced the starch level 82 to 98% by August 23. The May 23 treatment, applied while the plants were still emerging, had 146 mg/g starch on June 12, approximately the same as the control (140 mg/g). However, as the starch re- serves began increasing after this date in the control it con- tinued to decrease in the treated plants. Roots from plants 36 treated with terbacil at 2.2 kg/ha on June 12 had starch levels of 115.0 mg/g eight days after treatment. This indicates the beginning of a rapid drop in root starch while concurrently it was increasing in the non-treated check. Eventually the root reserves dropped to 11 mg/g starch on August 23. The depletion of starch caused by terbacil appeared to be inde- pendent of the date of treatment. Roots from all plants re— ceiving 2.2 kg/ha terbacil average 31 mg/g starch by August 23, a 92% decrease when compared to the control on the same date. Terbacil, when applied at 3.4 kg/ha (Figure 18) gave re- sults similar to that of the 2.2 kg/ha rate. A slight rise in root starch was noted at the first determination date after application for both the May 23 and the June 12 treatment. By July 5, however, both were significantly lower than the control. Similarly a slight rise was noted in root starch levels on July 25 after the June 12 treatment. However one month later, both the May 23 and the June 12 treatments had reduced the reserves to about 12 mg/g starch. The average for all the 3.4 kg/ha treatments was 38 mg/g root starch com- pared to 353 mg/9 starch in the control roots on August 23. Since glyphosate did not exhibit any soil activity, it was not used at the earliest date. The June 12 application of 2.2 kg/ha glyphosate appeared to cause a rise in root starch reserves by June 20 (Figure 2A). However, on July 5 the root starch content was about the same inroots of glyphosate ”El/Melt 54. A 4%: rem/ 37 Figure lA.--Effect of terbacil at 2.2 kg/ha on the starch reserve in horsenettle roots; a, control; b, applied May 23; c, applied June 12; d, applied June 20; e, applied July 5. ‘ B.--Effect of terbacil at 3.4 kg/ha on the starch reserve in horsenettle roots; a, control; b, applied May 23; c, applied June 12; d, applied June 20; e, applied July 5. **Means differ significantly from control at 1% level. 38 PLANT HEIGHT (cm) 0—5 2 0-05 3H0 60-75 60 -75 60-75 360 Am / a :1“ 2 so 3* .9 ya : \koi' e :4: z. b a 3w ‘3 o 3‘ 360 C E I g 270 a 3 l» 0 . o c m [,0 H58: “2 $0 % DATE 39 treated and check plants. The glyphosate applied on June 12, apparently inhibited an accumulation of starch after the ini- tial drop between June 20 and July 5. This early treatment gave a significant decrease in root starch at the last harvest date, August 23. When compared to the terbacil however, the 2.2 kg/ha glyphosate was not nearly as effective in reducing starch reserves. Applications at later dates did not signi- ficantly reduce the starch levels in the roots. Glyphosate at 4.5 kg/ha applied on June 12 significantly reduced the starch levels present on August 23 (Figure 28). The same rate applied on later dates did not reduce the starch levels significantly late in the season. The application of 4.5 kg/ha on July 5 caused a significant increase in root 'starch reserve by July 25 when compared to the control at the same date. Paraquat reduced the root starch content late in the sea- son only if applied while the plants were in early bloom (Table 4). Paraquat or glyphosate when in combination with terbacil. caused a significant decrease in root starch levels late in the season. Based on the data previously presented in Figure l, the major part of this decrease can be attributed to terbacil. llnicki gt gt. (7) conducted an investigation on root starch reserves of horsenettle in an abandoned field in New Jersey. They reported starch data from root sections in the upper 25 cm of the taproot and from the lower 25 cm. In the lower 25 cm of taproot, the starch reserve remained fairly 40 Figure 2A.--Effect of glyphosate at 2.2 kg/ha reserve in horsenettle roots; a, applied June 12; c, applied June July 5. B.--Effect of glyphosate at 4.5 kg/ha reserve in horsenettle roots: a, applied June 12; c, applied June July 5. **Means differ significantly from 1% level. on the starch control; b, 20; d, applied on the starch control; b, 20; d, applied control at 41 rum HEIGHT (cm) 0-5 20—35 35'60 60-7 60—75 60-75 -s~ V o 270 \. a A / 180 . o/ S? '3 90 '3 S 2‘ 1’ o a 3 360 o 6" 3 E d U I 270 U . a 1‘ ° ' I .- C m a / / 100 O/ 90 0 Xe if: 91’: 990 53 hi 953 .ummp .o.m.: m.»m¥=» an Pm>mp am on» an acmemeevv apucmopepcmvm no: mcouump cm__eem an umzoppoe mcamz\m e o.~e m~-oe eae_a ape; m\~ N.~+~.N Peeeeeue + meemeea»_a e e.m~ m~-oe scope mead m\~ e.m+_._ P.eeeeee + Seaeeeea a e.mem m~-oe scape open m\~ p._ eeeeaeaa ed e.me oe-mm scope »_eau o~\e ~.~+~.~ _.eeaeee + abemeeaapm e e.mm oe-mm saa_a spec“ o~\e e.m+~._ .Pueaee» + easeeeee mu a m.um~ oo-mm scape »_eeu o~\m F.P eeeaeeea e c.5m mm-m~ e:a-eea ~p\e ~.~+~.~ .eeeaeee + deemeeaapw e o.m~. mm-m~ use-eea ~P\e e.m+_._ __eaaeee + eeecaeaa a «.mem mm-m~ eea-eea ~F\e F._ Seeaeeee a :3 II 1.1 II II eeaz mu .u=< Am\mev Aebv soceum agape; macaw open Aunxmxv \m Seem eea_a agape ee.uau_.aa< deem eeeeaeee: .m~ umama< co mace; m—puocomco; :p mo>gomoc goeeam poo; on» co coeuacvasoo oupoeaco: use moumumaco; co oedema mghll.e open» 43 constant at about 40% starch. In the upper 25 cm of root however, the reserve dropped to 13% starch during early growth but within 8 weeks after emergence the starch content in both sections of root were comparable. Data obtained from the con- trol plants in this study approximate those obtained in New Jersey. Terbacil, a soil sterilant, was effective in reducing root starch and regrowth independent of the time of application or rate applied. Being relatively soluble in water (710 ppm) it will move deep into the soil horizon after sufficient rainfall (13). The persistance of this herbicide and its movement into the deeper horizon of the soil most likely was the predominant factor in the starch reductions obtained. The herbicide was absorbed by roots and moved via the xylem. Being a strong photosynthetic inhibitor (6) it killed new shoots as they emerged. The plants continued to hydrolize starch from deeper roots which in turn were depleted of starch. Glyphosate on the other hand has no soil activity and to control regrowth must translocate symplastically at toxic levels. Applications at 4.5 kg/ha, on July 5 was the only glyphosate treatment that adequately suppressed regrowth al- though defoliation was initially obtained with all the treat- ments. Three weeks after application there was a significant increase in the root starch level (104 mg/g) with this treatment. Since the increase could not have come via sugar production from photosynthetic activity it may be explained by the trans- 44 port of reserves from deeper root horizons. Glyphosate may have killed the active metabolic portions of roots, causing a decrease in the total root weight of the plants, hence an increase in starch present on a percentage basis in the re- maining living roots. This would require a redistribution of the reserves in the roots. 10. 45 Literature Cited Alberda, T. 1966. Responses of grasses to temperature and light. In The Growth of Cereals and Grasses. L. L. Milthrope and J. D. Ivens, eds. Butterworths. London. p 200-212. Arnold, W. E. and W. B. O'Neal. 1972. Canada thistle control with glyphosate and metribuzin. Proc. N. Centr. Weed Cont. Conf. 27:53. Baird, D. D. and G. F. Bergman. 1972. Post emergence characterization of a new quackgrass herbicide. Proc. Northeast Weed Sci. Soc. 26:100-106. J, , R. P. Upchurch, W. B. Homsley and J. E. Franz. 1971. Introduction of a new broad spectrum post emer- gence herbicide for herbaceous perennial weed control. Proc. N. Centr. Weed Contr. Conf. 26:64-68. Behrens, R. and M. Elakkad. 1972. Quackgrass control with glyphosate. Proc. N. Centr. Weed Contr. Conf. 27:54. Hilton, J. L., T. J. Monaco, 0. E. Moreland and W. A. Gentner. 1964. Mode of action of substituted uracil herbicides. Weeds. 12:129-131. llnicki, R. 0., T. F. Tisdell, S. N. Fertig and A. S. Furrer. 1962. Life history studies as related to weed control in the northeast. III-Horsenettle. North East Regional Pub. Bul. 368. McCready, R. M., J. Guggolz, V. Silvera and H. S. Owens. 1950. Determination of starch and amylase in vegetables. Anal. Chem. 22:1156-1158. Messersmith, C. G. 1972. Glyphosate for the control of leafy spurge and other perennial weeds. Proc. N. Centr. Weed Contr. Conf. 27:55. Muzik, T. 1970. Weed Biology and Control. McGraw-Hill Book Co. New York. . 11. 12. 13. 14. 15. 16. 46 Price, H. C. and V. J. Fisher. 1966.' Comparison of several substituted uracil herbicides for control of weeds around young peach and apple trees. Proc. Northeast Weed Contr. Conf. 20:174-177. Putnam, A. R. and H. C. Price. 1969. Tolerance of root- stocks and established Malus, Pyrus and Prunis trees to terbacil. Jour. Amer. Soc. Hort. Sci. 94(6):655- 658. and S. K. Ries. 1964. Herbicides for the control of perennial weeds in orchards. Res. Rep. of N. Centr. Weed Contr. Conf. 35. Skroch, W. A., and T. J. Sheets and J. W. Smith. 1971. Herbicides effectiveness, soil residues and phytotoxi- city to peach trees. Weed. Sci. 19:257-260. Smith, 0., G. M. Paulsin and C. A. Raguse. 1964. Extraction of total carbohydrates from grasses and legume tissue. Plant Physiol. 39:960-962. Yemm, E. W. and A. J. Willis. 1954. The estimation of carbohydrates in plant extracts by anthrone. Bioch. Jour. 57:508-514. CHAPTER 4 THE UPTAKE AND MOVEMENT OF C-LABELED GLYPHOSATE AND TERBACIL IN HORSENETTLE 14 ABSTRACT Both ‘4 C-labeled glyphosate [N-(phosphonomethyl)glycine] and terbacil (3-tgtt-butyl-5-chloro-6-methy1uracil) were ap- plied to the leaves of horsenettle (Solanum carolinense L.) at four stages of growth. Labeled terbacil was also applied to the roots via nutrient solution. The ‘4 C-methyl labeled glyphosate was readily absorbed and translocated to meriste- matic regions. Glyphosate translocation in older plants was over ten-fold that which occurred in younger plants although immature leaves of the younger plants initially abosrbed more herbicide. Translocation of glyphosate followed a source to sink pattern typical of phloem transported chemicals. Plants treated with 2-14 C-terbacil were uniformly labeled after uptake from nutrient solution indicating xylem transport. Only 0.5 to 1.0% of the applied terbacil was taken up by the 14 leaves. There was limited translocation of C after foliar terbacil applications. 47 48 INTRODUCTION Horsenettle (Solanum carolinense L.) is a persistant perennial weed in many orchards and fields in Michigan. The plant reproduces asexually by root sections which can develop shoots within 20 days after cutting (5). During a growing season, intact plants may produce several shoots along the fleshy storage root. Glyphosate (N-(phosphonomethyl)glycine) has been shown in our previous work to provide excellent season-long control when applied at 4.5 kg/ha while the plants were flowering. Applications at 2.2 kg/ha were not adequate regardless of tim- ing. Other workers have reported that the time of applica- tion is crucial for control of perennial weeds with glyphosate. Stoller (8) found yellow nutsedge (Cypgrus esculentus L.) was more susceptible if young plants were treated. Arnold (1) working with Canada thistle (Cirsium arvensis (L.) Soap.) and Messersmith (6) with both Canada thistle and field bind- wind (Convolvulus arvensis L.) found that fall applications were superior to those made in the spring. The control of quackgrass (Agropyron repens (L.) Beauv.) was improved if applications were delayed until the plants were 25 to 30 cm tall (2,7). In our earlier studies terbacil (3-tgtt-butyl-5-chloro- 6-methy1uracil) controlled horsenettle effectively indepen- dent of the time of application. Terbacil also caused a depletion of the root starch reserves late in the season. 49 This test was conducted to relate the control of horse- nettle with glyphosate and terbacil to the movement of these compounds within the plant and to determine if translocation was influenced by the stage of growth of the plant. MATERIALS AND METHODS Roots were collected March 15 in a field heavily infest- ed with horsenettle in southwestern Michigan. The roots were excavated, covered with soil and transported to the laboratory where they were refrigerated at 2.8 C. At intervals the roots were removed from the soil, washed with distilled water, out into 2 to 3 cm sections and planted in vermiculite. Root sec- tions were maintained in a growth chamber (32 C day for 14 hours at 17.2 klux and 24 C night) and allowed to develop new shoots. After shoots had emerged the plants were removed from the ver- miculite and placed in cups containing 120 ml of one-half strength Hoagland's solution (4) containing 8 mM N03 at pH 6.3. By suc- cessive plantings, plants were obtained that ranged from re- cently emerged to full flower. The 14C-methyl-labeled glyphosate was converted from the acid to the isopropylamine salt (formulated compound) by the addition of an equimolar amount of isopropylamine to 6.1 mg (66 uCi) of the acid in 3 m1 of deonized water containing 0.8% 1 Mon 0818 surfactant. One 10 ul drop containing 0.2 uCi of 1Mon 0818 is a non-ionic surfactant produced by Monsanto Com- pany, St. Louis, Missouri. 50 l4C-glyphosate was applied over the midrib of the third most recently expanded leaf. On the youngest plants, the most fully expanded leaf was treated. After treatment, the plants were placed in the growth chamber for 4 days under conditions pre- viously described. The 5.9 mg (30 uti) of 2-14 C-terbacil was initially dis- solved in 4 ml of acetone. A 0.54 ml aliquot of this stock solution was then placed into another vial and evaporated to dryness. Formulated terbacil (200 pl containing 3.7 g/l) was then added to the dried 2-14 C-terbacil and resuspended with an Aerograph Ultrasonic Cleaner. Three successive 10 ul drops were then applied to the leaf giving a total of 0.15 uCi per treated leaf. The plants were then maintained in the growth chamber for 4 days prior to assay. Labeled nutrient solution (5 uCi/l) was prepared by add- ing 1 ml of the stock 2-14 C-terbacil to 1500 m1 of half strength Hoagland's solution. Plants were put in cups containing 120 m1 of this solution and placed in the growth chamber for 12 hours. Each treatment was replicated 3 times on plants of 4 different stages of growth. At harvest, the plants were cut into five sections; 1, treated leaf; .2, acropetal to the treated leaf; 3, between the treated leaf and the storage root; 4, the storage root; 5, fibrous roots. The treated leaf was washed with five suc- cessive 50-m1 washes (glyphosate treated leaves were washed with water and the terbacil treated leaf with water : ethanol. 51 1:1 v:v) to remove the herbicide not absorbed. Plants treated with labeled terbacil in nutrient solution were plotted dry and quickly frozen with crushed dry ice. All of the plant parts were frozen and 1yophilized for 24 hours. One plant from each treatment was not sectioned. It was rehydrated, mounted and radioautographed for 5 or 14 days as described by Yamaguchi and Crafts (10). To show movement within the storage root, this organ was cut lengthwise prior to mounting. Each sample was then combusted with a Nuclear Chicago Model 3151 Oxidizer unit equipped with magnetic stirrers. If the dry weight of the sample was more than 50 mg, the sample was ground through a 20 mesh screen with a Wiley Mill and only 50 mg of the sample was combusted. Total dpm absorbed and translocated to other parts of the plant were based on the total weight of the plant section. One liter flasks were purged with oxygen and stoppered with rubber septum cups prior to combustion. Upon cooling of the flask, 10 ml of ethanol:ethanolamine (2:1 v:v) was in- jected and they were stirred for 15 minutes. One ml of the CO2 trapping solution was removed for liquid scintillation counting. A scintillation solution was prepared by dissolving 4 grams of 8801 [2,5,-bis-5-tgtt-butly-l-bensozexoly1 (2') thiopen] in one liter of toluene. The scintillation fluid had 63% efficiency as determined by External Standardization on a Packard Tricarb Scintillation 52 Spectrometer. All cpm (counts per minute) data were converted to dpm (disintegrations per minute). RESULTS AND DISCUSSION Uptake and translocation of ‘4 C-glyphosate in horsenettle. Glyphosate was readily absorbed by both immature and fully expanded leaves of horsenettle. Although the expanding leaves 14c, the fully ex- of the younger plants absorbed the most panded leaves on older plants exported more of the label to other plant parts (Table 1). Translocation increased with plant age reaching 76% of that absorbed on plants in the late flowering stage. Rate of export of glyphosate from leaves appears to be related to their capacity to produde and export sugars. Thrower (9) working with soybean showed that trans- location of photosynthates into and out of a leaf was a function of stage of develOpment. During early expansion, translocation was into the young leaf. As the leaf expanded transport be- came export. A similar phenomenon is apparently true with horsenettle. 14C was indicated even while Bidirectional transport of the plants were extremely young (Figure 1A). The label moved from the treated leaf via the phloem through the storage root and to another shoot on the same root section. It was noted however, that in the storage root, the 14C remained in the conductive tissue and did not appear to move out into the cortex. 53 Figure l.--Translocation of 14C-glyphosate and/or metabolites in horsenettle. The treated plant (left) and the corresponding radioautograph (right). A. Emergence B. Pre-Bud C. Early Flower 0 Late Flower 54 l l :1144' III till 56 .—m>o_ um um ucaovmwcmwm wagon ace—n zap: ammoco:_ geoc_p so» mapa> m \m .umma .o.m.4 an Po>op um use as ucocmcewu xppcmowmpcmpm ac: «gouump cop’spm an ooze—Foe memo: \m on mmom ommm Nmomm osmm ooomp a a.mp Logo”; one; pm coon mapw menu Nae. NNmmp a m.m saxopm a—Lem mu m¢m~ pmmu .mop coum m_e¢~ a N.“ van use m I 8m .8 82 $2: a E: 8:822.“ any mead cc?» no,» umaaaeh mo use muoom poem lace uoogm team «cozm can; noncomn< \m coraooopmcecp msoca_m omeeoum Peuoawmom pauoaocu< bounce» \m «sauna; mmeum peep; cowuoom acupm\zma .cpzocm ea moaeum Lace an mace—a opuuocmmco; c. muomocaa—mlu eo caramoopmcocu one mxmunal.F open» «p 57 14 In all the C-glyphosate treated plants the label appeared to move by the classic phloem transport mechanism described 14c by Crafts (3). Figures 1-B,C, and 0 all indicate that moved preferentially to the meristems, young leaves acropetal to the treated leaf, and fibrous roots. Only slight transport was noted to the older leaves basipetal to the treated leaf and above the storage root indicating little xylem transport following a basipetal phloem movement. However, transport occurred through branches leading to other active sinks (Figure 10). Our previous work indicated that both time of application and the rate of glyphosate are critical for control of horse- nettle regrowth following initial defoliation. Regrowth oc- curred if the plants were young with no flower buds present at the time of application. It appears that this may be re- lated to differential transport of the glyphosate and/or metabolites in younger and older plants. Young leaves, a1- through they readily absorb the herbicide do not export it as well as older leaves. Also on young plants, there is a rela- tively small leaf area to capture the glyphosate at treatment. These two factors in combination would decrease the effective- ness of the glyphosate and account for poor chronic toxicity at early stages of growth. The variable control of horsenettle at later stages of the plants development could also be related to two factors. The first would be differential metabolism of the glyphosate based on the age of the plant. Horsenettle, when it is most 58 susceptible to the herbicide may not metabolize it as rapidly as when it is either a much younger or much older plant. An- other factor is a delay in shoot development following the herbicide application. The storage organs of horsenettle are roots (5) with few buds already present. Buds will develop however, if the roots are sectioned as was done in this experi- ment or if the shoots are killed by a contact herbicide. The F? production of new shoots is not a rapid process, taking a mini- ' mum of 20 days for new shoots to emerge. When glyphosate is applied to actively growing plants, it is evident from the E radioautographs that it will quickly translocate to active meristems. These meristems along with the rest of the shoot may be killed within 2 weeks. In the storage root however, the active meristems are either not present at the time of appli- cation or can develop long after the treatment is applied. The storage root in this instance acts as a conduit and not as a sink for the herbicide. Here the glyphosate, although pre- sent. has no place to exert a herbicidal effect since there are no meristems present. Shoots will develop later on the storage organ, but by that time the herbicide may be inacti- vated or diluted to the point that the concentration is not high enough to control regrowth. This may explain the rate responses as related to chronic toxicity. Translocation of 2-14C-terbacil in horsenettle. In contrast to the variable control of horsenettle with glyphosate, our field test demonstrated that terbacil inhibits regrowth inde- 59 pendent of the time of application at 2.2 kg/ha. Terbacil is not readily absorbed by the leaves of horsenettle as is glyphosate (Table 2). Only 0.5 to 1.0% of that applied was absorbed by the treated leaves. There was some movement of 14C when applied to the leaf (Figure 2A). Much of that ab- sorbed moved acropetally in the treated leaf although there 14C down into the fibrous roots. 14 was slight transport of The primary transport of 2- C-terbacil when applied to the roots appears to be through the xylem (Table 3). 14C was uniformly translocated to all plant parts following a 12- hour exposure to the labeled terbacil in nutrient solution. As expected, more radioactivity was present in older larger plants. The control of horsenettle with terbacil is related to its being continually available to the roots, killing new shoots as they develop and causing a depletion of the starch reserves in the storage roots as was noted in our previous work. Foliar uptake probably does not contribute greatly to the toxicity obtained. 60 .umo» .o.m.4 x5 Fo>op mm ozu an ucogoeepu x—ucoowwrcm'm no: mgmuuop capweem ha cozoppoe memo: \m a Na «map vac vamp no man a mo.~ gazes; one; e um mmmp on “ma ~e~ Nee a mo.~ engage apgam a me cc. New now me. mam o mm.o can use a pm mu. Nam cow m- mam a so.o mucoucosu any cans ea.» ea.» vouamch we «so muooz aoom -coa uoogm icon uoozm ego; consomn< \l cowuoooPmcnch msogn'u «museum peuoaemom Fauoaoco< tonnage \m unease; macaw agape cowpuom pco~axtao on apauoemmsog mo mm>eop An moupponaume so\vce ppounsoulu ep .guzocm mo mommum Lace ea cowueuo—mcogu wen oxeunali.~ mpnmh 61 Figure 2.--Translocation of 14C-terbacil and/or metabolites in horsenettle. Treated plants (left) and cor- responding radioautographs (right). A. Leaf treated. 8. Roots treated. 62 63 Table 3.--Uptake and translocation of ‘4C-terbacil in horse- nettle when applied in nutrient solution. DPM/Section Plant Stage Fibrous Roots Storage Roots Shoots Emergence 895 353 1,769 Pre Bud 1087 679 11.519 10. 64 Literature Cited Arnold, W. E. and W. B. O'Neal. 1972. Canada thistle control with glyphsoate and metribuzin. Proc. N. Centr. Weed Cont. Conf. 27:53. Baird, D. D. and G. F. Bergman. 1972. Post emergence characterization of a new quackgrass herbicide. Proc. Northeast Weed Sci. Soc. 26:100-106. Crafts, A. S. 1967. Bidirectional movement of labeled tracers in soybean seedlings. Hilgardia 37:(16); 625-638. Hoagland, D. R. and D. I. Arnon. 1938. The water culture method for growing plants without soil. Univ. Calif. Agri. Exp. Sta. Circ. 347. llnicki, R. 0., T. F. Tisdell, S. N. Fertig and A. S. Furrer. 1962. Life history studies as related to weed control in the northeast. III-Horsenettle. North East Regional Pub. Bul. 368. Messersmith, C. G. 1972. Glyphosate for the control of leafy spurge and other perennial weeds. Proc. N. Centr. Weed Contr. Conf. 27:55. Sprankel, P. L. 1974 Factors affecting the herbicidal activity of N-Ephosphonomethyl)glycine (gly hosate) on quackgrass Agropyron repens (L.) Beauv.3 and in the soil. Ph.D. Thesis, Dept. of Crop and Soil Sci., Mich. State Univ., East Lansing, Michigan. Stoller, E. and L. Wax. 1972. Response of yellow nutsedge to bentazon, glyphosate and MBR 8521. Proc. N. Centr. Weed Contr. Conf. 27:55. Thrower, S. L. 1962. In Leopold, A. C. 1964. Plant Growth and Development. p71. McGraw-Hill Book Co. New York. Yamaguchi, S. and A. S. Crafts. 1964. The autoradiography of plant materials. Calif. Agr. Exp. Sta. Manual 35. LIST OF REFERENCES 10. LITERATURE CITED Ahlgren, G. H., G. C. Klingman and D. E. Wolf. 1951. Principles of Weed Control. John Wiley and Sons, New York. Alberda, T. 1966. Responses of grasses to temperature and light. In The Growth of Cereals and Grasses. L. L. Milthrope and J. D. Ivens, eds. Butterworths. London. p 200-212. Allen, H. H. 1934. Notes on recently observed exotic weeds; horsenettle and buffalo bur. Jour. Agr. New Zealand. 48:295-300. Arnold, W. E. and W. B. O'Neal. 1972. Canada thistle control with glyphosate and metribuzin. Proc. N. Centr. Weed Cont. Conf. 27:53. Ashton, F. M. and A. 5. Crafts. 1973. Mode of Action of Herbicides. John Wiley and Sons. New York. Baird, D. D. and G. F. Bergman. 1972. Post emergence characterization of a new quackgrass herbicide. Proc. Northeast Weed Sci. Soc. 26:100-106. , S. C. Phatak, R. P. Upchurch and G. F. Bergman. 1972. Glyphosate activity on quackgrass as influenced by mowing and rhizome density. Proc. Northeast Weed Contr. Conf. 27:13-20. , R. P. Upchurch, W. B. Homsley and J. E. Franz. 1971. Introduction of a new broad spectrum post emer- gence herbicide for herbaceous perennial weed control. Proc. N. Centr. Weed Contr. Conf. 26:64-68. Bandeen, J. D. and K. P. Bucholtz. 1967. Competitive ef- fects of quackgrass upon corn as modified by fertili- zation. Weeds. 15:220-223. Behrens, R. and M. Elakkad. 1972. Ouackgrass control with glyphosate. Proc. N. Centr. Weed Contr. Conf. 27:54. 65 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 66 Bellue, M. K. 1939. Carolina horsenettle, Solanum carolinense L., and other weedy Solanums in California. Ca1if.D§pt. of Agr. Bul. 28:471-478. Bradbury, H. E. 1956. Growth of horsenettle and evaluation of control methods. Unpublished Master's Thesis. Dept. of Farm Crops. Rutgers Univ., New Brunswick, New Jersey. Brockman, F. E., W. 8. Duke and J. F. Hunt. 1973. Agronomic factors affecting glyphosate for quackgrass control. Weed Sci. Soc. Amer. Abst. No. 27. Coupland, R. T. and G. W. Sellek and J. F. Alex. 1955. The reproductive capacity of vegetative buds on the underground parts of leafy spurge (Eurphorbia esula L.). Can. Jour. Agr. Sci. 35:477-484. Crafts, A. S. 1967. Bidirectional movement of labeled tracers in soybean seedlings. Hilgardia 37:(16); 625-638. Furtick, W. R. 1967. National and international weeds for weed science. A challenge for W.S.A. Weeds, 15:291-295. Gleason, H. A. 1968. The New Britton and Brown Illustrated Flora of the Northeastern United States and Adjacent Canada. Hafner Pub. Co., Inc. New York. Hamilton, K. C. and K. P. Busholtz. 1955. Effect of rhi- zomes of quackgrass (A re ron repens) and shading on seedling development a wee y spec es. Ecology. 36: 304-308. Hansen, A. A. 1921. Horsenettle. Pa. Agr. Ext. Weed Leaflet. 6:4. Hemphill, D. D. 1958. Poison ivy and horsenettle control beneath bearing apple trees. Weed Soc. Amer. Abst. No. 14. Hilton, J. L., T. J. Monaco, 0. E. Moreland and W. A. Gentner. 1964. Mode of action of substituted uracil herbicides. Weeds. 12:129-131. Hoagland, D. R. and D. I. Arnon. 1938. The waterculture method for growing plants without soil. Univ. Calif. Agri. Exp. Sta. Circ. 347. llnicki, R. 0., T. F. Tisdell, S. N. Fertig and A. S. Furrer. 1962. Life history studies as related to weed control in the northeast. III-Horsenettle. North East Regional Pub. Bul. 368. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 67 Jorgenson, E. and C. G. Messersmith. 1973. Control of field bindweed by subsurface layered and foliar applied herbicides. Proc. N. Cent. Weed Contr. Conf. 28:66. Klitz, B. F. 1930. Perennial weeds which spread vegeta- tively. Jour. Amer. Soc. Agron. 22:216-234. Klingman G. C. 1961. Weed Control as a Science. John Wiley and Sons, New York. Little, R. D. and R. S. McMurra . 1940. Solanum carolinense L. Pharmacent. Arch. 11(2); 23-28. McCready, R. M., J. Guggolz, V. Silvera and H. S. Owens. 1950. Determination of starch and amylase in vegetables. Anal. Chem. 22:1156-1158. Mc Indoo, N. E. 1935. The relative attractiveness of cer- tain solanaceous plants to the Colorado potato beetle, (Leptinotarsa decemlineata). Proc. Ent. Soc. Wash. 37(2):36-42. Messersmith, C. G. 1972. Glyphosate for the control of leafy spurge and other perennial weeds. Proc. N. Centr. Weed Contr. Conf. 27:55. Meuncher, W. C. 1955. Weeds. 2nd Ed. The MacMillan Co., New York. and W. T. Winne. 1942. Common poisonous plants. Cornell Ext. Bul. 539:26-37. Muzik, T. 1970. Weed Biology and Control. McGraw-Hill Book Co. New York. Neville H. W. 1950. A comparison of the effectiveness of certain chemicals in controlling horsenettle and other weeds in corn. Northeast Weed Contr. Conf. 4:217-219. Price, H. C. and V. J. Fisher. 1966. Comparison of several substituted uracil herbicides for control of weeds around young peach and apple trees. Proc. Northeast Weed Contr. Conf. 20:174-177. Pritchard, F. J. and W. S. Porte. 1921. Relation of horse- nettle (Solanum carolinengg L.) to leafspot (Septoria lycopersic). Jour. Agr. Res. 21°501-506. Putnam, A. R., A. P. Love, E. L. Silvia, G. Pagano and M. Van Buskirk. 1972. Horticulture report No. 21. Oct. 1972. Weed Contr. Res. Mich. State Univ., East Lansing, Michigan. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 68 and H. C. Price. 1969. Tolerance of root- stocks and established Malus, Pyrus and Prunis trees to terbacil. Jour. Amer. Soc. Hort. Sci. 94(6):655- 658. and S. K. Ries. 1964. Herbicides for the control of perennial weeds in orchards. Res. Rep. of N. Centr. Weed Contr. Conf. 35. Ray, 8. and M. Wilcox. 1969. Chemical fallow control of nutsedge. Weed Res. 9:86-94. Robbins, W. W., M. K. Bellue and W. S. Ball. 1956. Weeds a] of California. Calif. Dept. of Agri. Sacramento Print- ing Division (Document section). Skroch, W. A., and T. J. Sheets and J. W. Smith. 1971. Herbicides effectiveness, soil residues and phytotoxi- .~ city to peach trees. Weed. Sci. 19:257-260. ' Smith, 0., G. M. Paulsin and C. A. Raguse. 1964. Extraction of total carbohydrates from grasses and legume tissue. Plant Physiol. 39:960-962. Sprankel, P. L. 1974. Factors affecting the herbicidal activity of N-(phosphonomethyl)glycine (gly hosate) on quackgrass [A ro ron repens (L.) Beauv. and in the soil. Ph.D. Thes 5, Dept. of Crop and Soil Sci., Mich. State Univ., East Lansing, Michigan. , W. F. Meggit and D. Penner. 1972. Ouackgrass control with Mon 0468. Weed Sci. Soc. Amer. Abst. No. 157. Spurrier, E. C. 1973. Control of johnsongrass with gly- phosate as affected by rate of application and stage of maturity. Weed Sci. Soc. Amer. Abst. No. 28. Stoller, E. and L. Wax. 1972. Response of yellow nutsedge to bentazon, glyphosate and MBR 8251. Proc. N. Centr. Weed Contr. Conf. 27:55. Tweedy, J. A., G. Kapusta and O. Kale. 1972. The effect of several herbicides on nutsedge control in soybeans. Proc. N. Centr. Weed Contr. Conf. 27:28-29. Weeds of the North Central States. 1968. Univ. of 111. Agri. Exp. Sta. Circ. 718-p142. Upchurch, R. P., D. D. Baird and G. F. Bergman. 1972. Influence of temperature and diluent properties on Mon 0468 performance. Weed Sci. Soc. Amer. Abstr. No. 156. 51. 52. 53. 54. 69 Wallis, R. L. 1951. Potato psyllid selection of host plants. Jour. Econ. Ent. 44:815-817. Welbank, P. J. 1961. A study of nitrogen and water fac- tors in competition with ro ron repens (L. ) Beauv. Ann. of Botan. 25: 116- 13;. Yamaguchi, S. and A. S. Crafts. 1964. The autoradiography of plant materials. Calif. Agr. Exp. Sta. Manual 35. Yemm, E. W. and A. J. Willis. 1954. The estimation of carbohydrates in plant extracts by anthrone. Boich. Jour. 57:508-514. APPENDICES APPENDIX A Hoagland's Solution 7a Chemical Stock solution Final solution (all) (ml stock/l H20) A Fe (Chelate 12%) 16.6 2.5 i B KHZPO4 27.2 2.5 C MgSO4 3 7H20 98.6 2.5 0 K2504 87 1.0 E Minor elements: 1.25 ZnSO4- 7H20 0.088 H3804 1.144 MnClz- 4H20 0.724 CuSO4- 5H20 0.032 H2M04- H20 0.008 F KNO3 101.11 G Ca(NO3)2- 4H20 236.16 H CaClZo ZHZO 147 1.5 Equal quantities of F and G for the following NO3 concentrations: 2 mM 3 mM 4 mM 8 mM 12 mM 16 mM m1 stock/1 H20: 0.66 0.99 1.33 2.66 3.99 5.32 7O 71 APPENDIX B Perennial Weed Control on Non-Crop Land Location: Soil type: Application date: Conditions: Plot size: 6 x 25 Weeds present: Sodus Experimental Farm Genesee sand clay loam June 11. 1971 (terbacil), July 14, 1971 (glyphosate) Plot area was plowed, dragged and disked 4 weeks prior to spraying. Replications: 4 GPA: 36 Ouackgrass, Canada thistle, Horsenettle, Common milkweed, Hedge bindweed, Swamp smartweed. Weed Control Ratings (June 3) Herbicide (£353.) Broadleaf Ouackgrass None —— 1.0 1.0 Terbacil 1.1 5.0 3.3 Terbacil 2.2 16.0 3.8 Glyphosate 2.2 7.3 7.3 Glyphosate 4.5 8.5 9.0 Glyphosate + Terbacil 2.2+2.2 8.8 8.8 Horsenettle Control Location: Soil type: Application dates: 72 APPENDIX C in a 2 Year-01d Asparagus Planting Decatur, MI Oshtemo loamy sand June 20, 1972, soil dry - 80°, air temp. - 88°, horsenettle size - 20 to 30 cm, August 22,1972, soil - 82°. air temp. - 90°. Plot size: 3 x 25 Replications: 3 GPA: 72 Note: Applications were directed on each side of the asparagus row with a single nozzle boom to prevent as much spray as possible from reaching the asparagus fern. Ratings Horse- Horse- Horse- Treatment Rate Surfactant nettle nettle nettle (kg/ha) 8—8—72 8-22-72 9-21-72 Glyphosate* 2.2 None 6.0 6.3 8.0 Glyphosate* 4.5 None 7.0 6.7 8.0 Terbacil 2.2 x-77 (.5%) 7.7 8.3 8.0 Glyphosate* 2.2 Fomex (.751) 3.7 5.0 7.0 Glyphosate* 4.5 Fonex (.75%) 4.7 6.3 8.0 Terbacil 2.2 Fonex (.75%) 7.7 8.0 8.0 LSD at 5% level 3.2 4.2 2.9 Coefficient of variation (%) 19 23 13 *Received a second application 8-22-72. 73 APPENDIX D Horsenettle and Ouackgrass Control in a Tart Cherry Orchard Location: Honor, MI Soil type: Plainfield sand Tree age: 12 years Application date: June 13, 1972 Conditions: Soil - 81° - dry, air temp. - 87°, Weeds were 10 to 15 cm high when sprayed. Plot size: 8 x 8 Replications: 3 GPA: 72 ,Ratings Treatment Rate Surfactant Horsenettle Horsenettle (kg/ha) ‘ 7-13-72 8-10-72 Glyphosate 2.2 None 6.3 6.0 Glyphosate 4.5 None 7.7 7.0 Terbacil 2.2 X-77 (.5%) 4.3 6.3 Glyphosate 2.2 Fomex (.75%) 7.0 5.3 Glyphosate 4.5 Fomex (.75%) 5.7 6.0 Terbacil 2.2 Fomex (.75%) 5.3 7.0 LSD at 5% level 3.6 4.2 Coefficient of variation (%) 3O 29 HICHI N TATE UN V 1111 A 11 11311131111115 Hill 1 29 18682 S III" 3 31