STUDIES OF THE INFLUENCE OF PESTICIDES ON GROWTH AND YIELDS OF VEGETABLES Thesis for the Degree of M .. 8.. MICHIGAN STATE UNIVERSITY DENNIS EDWARD DEYTON 1973 IIIJIIIIIHZIIIJMIIIIIIIIIIIIIIIILIUIIIIIIIII L jug”. University ABSTRACT STUDIES OF THE INFLUENCE OF PESTICIDES ON GROWTH AND YIELDS 0F VEGETABLES By Dennis Edward Deyton Two years results indicated that pesticides may influence growth and yield of vegetable crops in ways other than by pest control. Several agricultural chemicals were shown to increase early yields of muskmelons (Cucumis melo L. cv. Burpee Hybrid) and tomatoes (Lyggr persicon esculentum L. cv. Jet Star) in l972. Disulfoton (9,9;diethyl §7(2-[ethylthio] ethyl) phosphorodithioate) at l.12 kg/ha was especially effective for increasing early melon yield. Agricultural chemicals were more effective in altering plant growth under less desirable grow- ing conditions of l972. than in l97l. Total melon weights in 1972 were increased significantly by bensulide (§;(9.deiisopropyl phosphoroe dithioate ester of 57(2-mercaptoethyl) benzenesulfonamide), naptalam (er-napthylphthalamic acid), trifluralin (g,g.g7trifluoroe2,6odinitrooN, N:dipropyl-p:toluidine), and disulfoton with the lowest concentrations generally resulting in largest increase in yield. Largest yield for each chemical occurred at 3.4 kg/ha of dinoseb (2,4-dinitro-6-gggrbutyl- phenol) 3.41 kg/ha of bensulide, 2.2 kg/ha of naptalan and l.l or 2.2 kg/ha of disulfoton. Dennis Edward Deyton Flowering of tomato plants was modified byapplication of dinoseb, naptalam, and disulfoton. These chemicals were observed to increase fasciated flowers, and polychotomous branching of clusters. Naptalam significantly increased the occurrence of seedlessness. Yield of beans (Phaselous vulgaris L. cv. Pr6vider) was increased by all chemicals, except naptalam. Trifluralin and disulfoton resulted in the largest increases in yield. The increased yield corresponded to increased stand with each chemical except naptalam. Lowest concen- trations gave greater increases of yield or stand.than the control. STUDIES OF THE INFLUENCE OF PESTICIDES ON GROWTH AND YIELDS 0F VEGETABLES By Dennis Edward Deyton A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Horticulture 1973 ACKNOWLEDGMENTS The author wishes to express his appreciation to R. L. Carolus for his assistance and guidance as a major professor. Sincere thanks are also extended to Dr. H. C. Price and Dr. D. Penner for their valuable assistance. The author wishes to express special appreciation for the friend- ship and encouragement of his parents. Mr. and Mrs. Edwin Y. Deyton. Ii LIST or TABLES . . . LIST OF FIGURES. . . INTRODUCTION . . . . REVIEW OF LITERATURE . MATERIALS AND METHODS. TABLE OF CONTENTS Horticulture Farm, l97l ...... . . . . . ....... Aurelius Farm, l972 . RESULTS. 0 o o o o Pesticide effects on vegetable plants in 1971 . ..... . Melons . . Tomatoes 0 O O O O O O O BeanSo O O O O O O O O O O Zucchini squash. . . . . Effect on composition of tomato and melon leaves . . . Pesticide effects on vegetable plants in 1972 ....... Treatment Effects on muskmelon ..... . ...... Early yield of melons . . . . . . . . . . . . . . Total yield of melons .............. Treatment Effects on Tomatoes. . . . ......... Early growth and floral development ....... Fruit 0 o o o o 9 o o o o o o o o ‘ o o o o o o o o o o o o o o o o o o o o o o o o o o o o o 0 yield 0 O O O O O O O O O 0 O O 0 O 0 O O 0 Chemical Treatment on Beans. ............. GENERAL DISCUSSION . LITERATURE CITED . . . Page iv vi TABLE 10. II. 12. 13. l4. LIST OF TABLES Treatment applications of 1971 and 1972. . . . . . . . . . . Common and scientific names of chemicals used in 1971 and 1972 O O O O O O O O O O O O O O O O O O O O O O O O O O O 0 Effect of agricultural chemicals on melon (cv. Burpee Hybrid) yield. 197]. O O O O 0 O O O O O O O O O 0 O O O O 0 Effect of agricultural chemicals on tomato (cv. Campbell _ 72])yie1d’19710000000000.coo...ooooo Effect of agricultural chemicals on green bean (cv.) Provider) yield, l97l. . . . . . . . . . . . . . . . . . . . The Effect of dinoseb, trifluralin, and simazine.on.Zucchini squaSh’ 197] O O O O O I O O O O O O D O O O O O O O O O O O . Effects of agricultural chemicals on mineralconcentration in tomato and melon leaves, 1971 . . . . . . . . . . . . . . The effects of pesticides on early yield of melon (cv. Burpee Hybrid), l972 . . . . . . . . . . . . . . . . . . . . The effect of three rates of five chemicals on early yield I of melons (cv. Burpee Hybrid), 1972. . . ..... . . . . . The effect of pesticides on total yield of melon (cv. Burpee Hybrid), 1972 . . . . . . . . . . . . . . . . . . . . . Effect of three rates of application of five.pesticjdes on.. total number of melons (cv. Burpee Hybrid), 1972 . . . . . . The effect of pesticides on growth and flowering of tomato ‘ (cv. Jet Star) plants, August 10, 1972 . . . . , . . . . . . The effects of three rates of five chemicals on flower I number and vine weight of tomato (cv. Jet Star), August 10, 1972 O O O O O O I O O O 0 O O ....... O O O O O 0 O O The effect of pesticides on number of flowers, fruit, flower cluster, and on vine weight of tomato (cv. Jet Star) plants, . 1 972 I O O O O O O O O O O O O .0 O O O O O O O O O O O I 9 0 iv Page 13 l4 17 18 20 21 22 24 26 28 ‘29 34 35 37 LIST OF TABLES—-continued TABLE Page 15. The effect of pesticides on yield of tomato fruit (cv. Jet Star). 1972. O C O O O O O O O O O O O O O O O Q 0 O O O 4] 16. The effect of three rates of five chemicals on yield of tomatoes (cv. Jet Star), 1972. . . . . . . . . . . . . . . . 42 17. Effect of two.rates of five pesticides on green beans.(cv. Provider). 1972. . . . . . . . . . . . . . . . . . ..... 46 LIST OF FIGURES FIGURE I. The influence of agricultural chemicals on the early and total weight of marketable and nonmarketable melons (Cucumis melo L. Burpee Hybrid), l972. . . . . . . . . . . . The effect of agricultural chemicals on flowering and fruit- ing of tomatoes (Lycopersicon esculentum L. cv. Jet Star), 1972. A. Fasicated flowers of plants treates with 2.2.kg/ha of naptalam,.B. Seedless fruit of plants treated with disul- foton and seeded fruit of control plants . . . . . . . . . . The influence of agricultural chemicals on early and.total weight of marketable tomatoes (Lycopersicon esculentum L.cv. Jet Star)’ 1972. O O O 9 0 O I O D O O O O O Q 0 O O Y'. O O 0 Comparison of the mean daily temperature and also the mean monthly temperature for the month of June for 1971. 1972, and a 30 year average. . . . . . . . . . . . . . . . . . . . vi Page 32 4O 45 53 INTRODUCTION Pesticides are valued for their control of undesirable pests. Their value is generally determined by their ability to control a pest without excessive damage to the crop. Thus, pesticide research has often centered upon what chemicals will provide adequate control of a pest with minimum acceptable damage to the crop. Although the importance of research emphasis on pest control is self- evident, perhaps more emphasis should be placed on the direct effect of the chemiCals on crop growth. The gaining of "a better understanding of the existing herbicides might be more productive than the continued research and development of new pesticides" (63). It has often been difficult to determine what might have been direct effects on crop growth. There have been numerous reports of yield increases associated with pesticide use. Difficulty lies in determining if the increase was due to elimination of the pest or if some increase may have been contributed to a direct stimulation of crop growth. It is especially interesting to observe the activity of herbicides, which may retard growth of some plants. not effect the growth of others. and may even stimulate growth in some plants. Devlin (11) defines plant growth regulators as organic compounds which in small amounts promote. inhibit. or otherwise modify any physio- logical processes in plants. Thus many of our organic herbiCides, which are often used in very small quantities may meet the criteria of this definition. Even sublethal concentrations of pesticides that would not control pests can modify the growth of plants (58). The purpose of this study was to determine the influence of pest- icides on the growth of vegetable plants. Special emphasis will be placed on determining promotion of plant growth. REVIEW OF LITERATURE Pesticides may influence plant growth in various ways. More obvious additional influences of a pesticide may be in supplying of some nutrient‘ to plants. For example, Klingman (27) recommended the use of ammonium nitrate solution as a directed contact herbicide for corn. The spray solution served the dual benefit of controlling weed growth and supplying nitrogen to corn. The metal based fungicides supply trace nutrients to plants. Appli- cation of zineb (zinc ethylenebisdithiocarbamate), a fungicide, has resulted in a ten-fold increase in zinc accumulation in strawberries (10). This is an obvious benefit where zinc is deficient. Increased yields of ‘ grapes treated with zineb were reported by Baldacci and Bonola (6); and Webster gt 31, (56) reported that another fungicide, maneb (manganese ethylene-l,2-bisdithiocarbamate) stimulated growth 0f lima bean plants. Many other pesticides have been reported to canse an increase in growth or development by some manner more complex than just supplying a deficient nutrient. Hughes (22) reported that the insecticide, dieldrin (1,2.3,4,l0,10-hexach1oro-exo-6,7-epoxy-l,4,4a,5.6,7,8,8a-octahydro-1,4- endo-exo-S.8-dimethanonaphthalene), stimulated an increase in mean fresh weight of harvested cabbage that could not be attributed to insect con- trol. Maclagan (32) reported that dieldrin and BHC (benzene hexachloride) stimulated growth and development of a larger percentage of longer roots in parsnip seedlings. Allen and Casida (4) found that BHC stimulated bean stem growth and Gould (16) found that it affected floral growth of tomatoes, with aerial applications to blossoms resulting in a marked increase in tomato yield. Another insecticide, aldrin (l,2,3,4,10,10- hexachloro-l,4,4a,5,8,8a-hexahydro-l,4-endo-exo-5,8-dimethano-naphthalene), has been reported by Jones (23) to stimulate an increase in the yield of carrots, which could not be attributed to insect control. Long §§;§l, (29) reported that during the first 11 weeks of growth under greenhouse conditions, chlorodane (octachloro-4,7-methanotetrahydro- indane) enhanced sugar cane growth by 58%, while insects were responsible for reductions in plant weight ranging from 2l to 30%. TThey Observed that, "It seems likely that the stimulating effects of chlorodane on growth may be at least as important as the control of any anthropod pest." Several researchers have found that DDT (dichloro diphenyl trichloro- ethane) may have a regulatory effect on plant growth. Chapman and Allen (9) found that higher concentrations of DDT restricted plant growth, yet lower concentrations stimulated growth in some plants. Aerial applications stimulated maximum vegetative growth of squash and cucumber at 0.0005 per- cent, tomato at 0.008 percent, and carrot and potato at 0.512 percent. They suggested that the effects of DDT "closely resemble that of some plant hormones." Allen and Casida (4) noted DDT stimulated bean stem growth when auxin was absent in nutrient solution. A possible relation- ship was suggested between DDT and auxin. Besides affecting vegetative growth, DDT at low rates has been observed to affect floral development. Chapman and Allen (9) observed in cucumbers that as DDT stimulated vegetative growth, the number of blossoms also increased proportionally. Rao (44) reported that Spraying tomato vines with DDT resulted in 4.8 fruit weighing 95 grams compared to 0.38 fruit per vine weighing 6.2 grams on unsprayed plants, which was appar- ently due to stimulation as there was no insect infestion problem. Brown gt_gl, (7) cited an increase in cotton boll production and yield when DDT was applied at weekly intervals beginning with the appear- ance of the first squares and flowers. This increase occurred without effecting leaf number or dry weight. Hacskalyo ahd Scales (18) observed that DDT in combination with dieldrin retarded flower formation, boll set, and plant growth. They also noted that the systemic insecticide Guthion (9,9:dimethyl.§y(4-oxo-l,2,3-benzotrianzin-3(4H)-lymethyl) phosphorodi- thioate) at 0.25 lb/A increased the number of flowers on cotton plants. Herbicides also function as growth regulators. Taylor and Arnst (53) reported that trifluralin (_a_,g,g_-trifluoro-2,6-dinitro-N,flrdipropyl-p_- toluidine) at l lb/A preplant incorporated resulted in a 40% pea yield increase. ‘As the experiment was designed to examine weed control, the question remains whether the increased yield was due only to weed control or partially to growth stimulation. Kesner and Ries (26), examining the effect of low concentrations of diphenamid (N,N;dimethyl-2,2-dipheny1acetamide) on tomato plants in pots found low concentrations enhanced vine growth. Diphenamid was observed to increase the growth of two fungi whose filtrate stimulated growth. Researchers have tried to determine how herbicides may affect plant growth. Many have noted an effect on ion uptake or accumulation in the plant. For example, Ries gt_gl, (46), reported that peach.trees treated with a mixture of simazine (2-chloro-4,6-bis(ethyl amino)-§;triazine), amitrole (3-amino-l,2,4-triazole), and amitrole-T (amitrole plus ammonium thiocyanate) contained higher leaf nitrogen and produced longer terminal growth than trees where weeds were controlled by hand. The concentration of other ions has been found to be influenced by the concentration of the '7'"” triazines. Millikan gt_gl, (35) found that simazine concentration of i 0.5, l, and 2 ppm resulted in an increase in phosphorus and zinc concen- I trations in the first true leaves of soybeans. Other ions observed to increase were K, Mn, and Si while Ca, Mg, 8, Sr, Mo, Co, and Ba were Isa—r reduced by'more than 50% as compared to high phosphorus treatments. Ruiz (49) found that l/8 lb/A of simazine applied on peas resulted in an increase in K and Ca accumulation. Researchers have reported various results for the phenol herbicides. Hojtasek (60) conducted a test to determine how DNBP (4,6-dinitro-o-sgg; butylphenol) inhibited accumulation of P32 and the incorporation of ADP into ATP. Ruiz (49) found that DNBP caused a 25% increase in accumulation of phosphorus and reduced sodium accumulation by 65% in peas and that combinations involving DNBP resulted in over a 25% increase in Cu and Zn accumulation. Nwachuka (40) indicated that DNP reduced potassium uptake of castor bean plants grown in water culture, but sodium absorption was increased. Nashed and Ilnicki (38) observed an increase absorption of calcium and sulfate from nutrient solution by juvenile corn, soybeans, and large crabgrass when treated by linuron (3-[3,4-dichlorophenyl]—l-methoxy-l- methylurea). Houge (21) conducted a test noting the effects of both ‘. 5i lethal and sublethal concentrations of linuron on tomatoes and parsnips. The foliar application of both sublethal (1/2 lb/A) and lethal concentra— tion (2 lb/A) stimulated the uptake of P32 from a nutrient culture solution. Also, there was stimulation of P32 translocation to the leaves. The in- creased P32 seemed to be associated with the inorganic phosphate fraction. Contrary to Nashed and Ilnicki's report of increased Ca absorption in several crops, Houge (21) reported that linuron inhibited absorption and translocation of Ca45 in tomatoes and parsnips. There have been reports of growth regulating properties associated with the chlorophenoxy herbicides. Diem and Davis (13) reported that 2,4-D (2,4-dichlorophenoxyacetic acid) at low concentrations of 10"10 to 7 45 with higher con- 10' M resulted in increased absorption of water and Ca centrations reducing absorption. Wort (61) observed that a 0.1% concen- tration of 2,4-D at 12 lb/A gave an 11 to 13% increase in growth and 23 to 40% increase in yield of green beans. Rathore and Wort (45) applied sprays containing l ppm of 2,4-D with or without the micronutrients Fe,, Mg, Ca, Zn and B at 5 X 10-4 M. Largest increases in growth of bean plants resulted from the combination of 2,4-D plus micronutrients. The combination resulted in an increase of green pod weight of 27%. The 2,4-D may in some manner have aided in the absorption of the micronutrients, although an analysis was not reported of the concentrations in the plant. Some chlorophenoxy type compounds have been shown to influence the flowering of plants. Para-chlorophenoxyacetic acid and 4-chlorophenoxya- acetic acid have been effective inducers of seedlessness in tomato fruit (28,l9). Marth and Webster (31) reported that the herbicide fli- '. 2,4,5~T applied on lima beans resulted in “apparent overall stimulation in plant growth manifested by moderate increase in size of the plant." Pesticides probably influence plant growth in many ways. Nashed and Ilnicki (38) stated that "changes in ion uptake in herbicide treated plants may be symptomatic of basic changes in metabolism or of changes in the permeability characteristic of plant membranes." Herbicides such as chlorophenoxy type may upset the hormonal balance in the plant. Neintraub (57) reported that 2,4-0 treatments lowered the auxin content of beans and Henderson ;§__l. (20) showed that 2,4-D increased the rate of destruction of IAA in sections of pea stems. Houge (21) suggested that linuron may possess kinin type activity since it was observed to delay senescence of tomato leaf disks. Nashed and Ilnicki (38) suggested that linuron possibly changed the permeability characteristics of cell membranes of soybeans because of observed loss of Mg. Price (42) indicated that some relationship existed between dichlobenil and calcium in maintaining plant membrane integrity in beet roots. Another herbicide has been observed to possibly retard the rate of breakdown of protein or its loss from the plant. Agbakda and Goodin (3) reported paraquat (1,1'-dimethyl-4,4°-dipyridylium cation) treated costal bermuda grass contained more nitrogen than control plants, apparently,due to retarding the rate of loss of nitrogen. In conclusion, numerous researchers have reported some rather pro— nounced variations in growth and development with pesticide treatment. It is often difficult to determine if increased yields are due to elimination of pests or to a direct effect on the plant. There is evidence that the pesticides affect the physiological functions of the plant, such as membrane integrity and perhaps the hormonal balance of the plant. MATERIALS AND METHODS Horticulture Farm, 1971 Field studies were undertaken during the summer of 1971 at the Horticultural Research Center to determine the effects of pesticides on selected vegetable crops. One experiment involved muskmelon (Cucumis mglg_L. cv. Burpee Hybrid Melon) plants transplanted on June 17, five 2 plant pots to a.plot, 1.53 meters apart in rows 1.83 meters apart. In another experiment, 6 tomato (Lycopersicon esculentum L. cv. Campbell 721) plants were similarly transplanted .92 meters apart in rows 1.53 meters apart. One-fourth liter of 10-52-8 (1.36 kg/189 liter) was applied to each plant. The starter solution also contained the systemic insecticide diazinon 218 grams/189 liter, ai. In a third experiment, 17 green bean (Phaselous vulgaris L. cv. Provider) seeds were planted per 1.22 meter plot on July 2. Each experiment consisted of 16 treatments in a randomized block design with two replicates. The treatments consisted of seven chemicals applied at two concentrations plus two controls (Table 1A). All treatments were applied the morning of June 17 before trans- planting tomato and melon plants. The chemicals were sprayed on to 9.15 X 0.92 meter plots using a C02 sprayer. All crops were sprayed, cultivated, and hand hoed as required during the season. Melons were harvested and yield data recorded from August 26 IO II through October 1, tomatoes from September 13 through October 7, and beans on August 25, September 1, and September 7. I Abnormal growth and development as influenced by the chemical treatments was noted. Leaves were analyzed to determine if nutrient concentration was influenced by treatment. On September 4 leaf samples were taken from melon and tomato plants and oven dried at 150°F. Nitrogen was determined by the Kjeldahl method, potassium with a flame photometer, and P, Na, Ca, Mg, Fe, Cu, 8, Zn, and Al by spectrophotometer. Zucchini squash (Cucurbita pepo) were transplanted June 25, 0.92 meters apart in rows 1.22 meters apart and 2.75 meters long. Squash were also seeded June 28 in a separate plot at similar spacings. Plots received treatments of either 2.24 kg/ha of dinoseb, 0.84 kg/ha of tri- furalin, 0.28 kg/ha of simazine, or no chemicals. Treatments were applied June 5 over foliage and irrigated afterwards. Aurelius Farm, 1972 Field studies were conducted at the Aurelius farm during 1972. Peat pot grown Burpee Hybrid muskmelons were planted June 5, 5 per plot 1.22 meters apart in rows 1.68 meters apart. Peat pot grown Jet Star tomatoes were planted in the field on June 5, 6 per plot spaced 0.92 meters apart in rows 1.68 meters apart. Each transplant received starter solu- tions. Each experiment consisted of 16 treatments with three replicates. Treatments consisted of 5 chemicals applied at three concentrations plus the control (Table 18). 12 The chemicals were applied to a 5.49 X 0.92 meter plot for tomatoes and 6.10 X 0.92 plot for muskmelons. Bensulide was sprayed over the plants using a C0 sprayer and immediately attempted to wash it off. 2 Trifluralin and disulfoton were applied in granular form with effort taken to avoid crop foliage. The treatments of dinoseb were added to a large volume of water (6778 l/ha) and sprinkled onto the plots with a sprinkling can. Naptalam applied on June 20 was applied in spray form while that applied June 27 was sprinkled onto the plots. After the application on June 27, the chemicals were incorporated by raking the soil. Provider green beans were seeded June 12 into 4.88 X .92 meter plots. Applied chemicals covered the entire plot. Treatment plots were 1.83 meters apart with a guard row between. Only the center 3.05 meters of each treatment plot was harvested for record. Treatments for beans were similar to those used on muskmelons and tomatoes, except intermediate concentrations of dinoseb and disulfoton were deleted (Table 1C). The treatments for each experiment were in a randomized block design with three replicates. All experiments were on a sandy loam soil that had been previously fertilized with 448 kg/ha of 10-20-20 and later side- dressed with 168 kg/ha of ammonium nitrate. The soil had been treated in late April with 2.2 kg/ha of Amitrole T. Need competition was minimized by hand and tractor cultivation. Observations of bean growth and of melon vine growth were made through the season. Beans were harvested from August 5 through August 21. After the final harvest. bean vines were counted, cut off at ground level and the vines weighed. Melons were harvested September 5 through 13 Table 1. Treatment applications for 1971 and 1972. lA. Treatment applications to muskmelons (cv. Burpee Hybrid) and tomatoes (cv. Campbell 721), 1971. chemical' _kg/ha, ai (low trt rate) (high trt rate) Captan 50% NP 4.48 13.45 Carbaryl 50% NP 4.48 13.45 Alar 85% NP 4.48 13.45 Diazinon 84% NP 3.36 10.09 Bensulide 4EC 3.36 10.09 Simazine 80% NP 0.14 0.42 Solan 4EC 3.36 10.09 Control -- ----------_------------------------------—---------------------- ---------- lB. Treatment applications to muskmelons (cv° Burpee Hybrid) and tomatoes ° (cv. Jet Star), 1972. chemical kg/ha, ai Date (low trt rate) (interm trt rate) (high trt rate) App. Bensulide 4EC 3.36 6.73 13.45 6/20 Trifluralin 5% G 0.56 1.12 1.68 6/27 Dinoseb 5EC 3.36 6.73 13.45 6/27 Disulfoton 15% G 1.12 2.24 . 4.48 6/27 Naptalam 2EC 2.24* 4.48 8.97 6/27 Control -- ~- -- 1C. Treatment applications to green beans (cv. Provider), 1972. chemical kg/ha Date (low trt rate) (interm trt rate) (high trt rate) App. Bensulide 4EC 3.36 6.73 13.45 6/20 Trifluralin 5% G 0.56 1.12 1.68 6/27 .Dinoseb 5EC 3.36 -- 13.45 6/27 Disulfoton 15% G 1.12 w- 4.48 6/27 Naptalam 2EC 2.24* 4.48 8.97 6/27 Control -- -- -— *Low rate of naptalam applied on 6/20. I4 Table 2. Common and scientific names of chemicals used in 1971 and 1972. Common name Scientific name Alar Succinic acid 2,2-dimethyl hydrazide Bensulide __-(O,_ O- Diisopropyl phOSphorodithioate ester of N_(2- mercaptoethyl benezesulfonamide Captan Cis-N:([Trichloromethy1]thio)-4-cyclohexene-l,2- dicarboximide Carbaryl l-Naphthyl-N-methylcarbamate Diazinon 0,0-Diethyl-O-(2-isopropyl-6—methy1-4- pyrimidinyl)phosphorothioate Dinoseb 2,4,0-Dinitro-6-sggybuty1phenol Disulfoton Q,Q:Diethyl-5-(2[ethy1sulfinleethyl) phosphorodi- thioate Simazine 2-Chloro-4,6-bis(ethyl amino)—§:triazine Solan Chloro-2-methylfp-valerotoluidide Trifluralin g,g_,g—Tri fl uoro-2 ,6- di ni tro-_N_,N_-dipropyl -p- toluidine IS September 25 and the number and weight of marketable and unmarketable fruit recorded. Pesticide effects on tomato growth were observed during the growing season. Because of observed differences in flowering, one plant from each plot of dinoseb, disulfoton, naptalam, and control treatments was removed on August 10 for careful examination. Data on the number of flowers showing yellow and the number of small and large fruits were recorded. Later, a second plant was removed from each plot in the first replication and counts made of cluster number, flower number, fruit number, and fruit and vine Weight. Tomatoes were harvested from August 5 through September 6 and records kept of number and weight of marketable and unmarketable fruit. By early September the plants appeared to have been striken by mosiac virus. Thus in order to attain an estimate of later yield, all fruits .8 centimeter or larger were removed, counted, and weighed on September 10. The data were submitted to analysis of variance and Duncan's Multiple Range Test was used to determine the difference between means. RESULTS Pesticide Effects on Vegetable Plants in 1971 Melons A statistical analysis of melon yield data indicated that none of the chemicals significantly affected either early or total yield. Although no treatment altered early yield significantly, all treatments markedly reduced the number of melons harvested early in the season with simazine causing the greatest reduction (Table 3). The chemicals had no significant effect on the total number of marketable melons, although there was a trend of all chemicals except Alar to decrease the number of melons. Also, there was a trend for chemicals to reduce the weight of marketable melons, though not signifi- cantly. 1 None of the treatments caused significant differences in the total yield of marketable and unmarketable fruit. All treatments except diazinon caused reductions in the number of melons harvested (Table 3). Tomatoes Although the applied chemicals had no significant effect on the yield of tomatoes, there was a trend for diazinon, captan, carbaryl, alar, bensulide, and solan to increase early marketable number and weight slightly. Simazine tended to reduce both early and total yield; other treatments tended to increase total yield slight1y(Table 4). 16 I7 .ummh magma m—awppaz m.cmu;:o uc+mz Fm>mp mo. mgp um “cwuwewcmwmcoc mew memos Fpgvx u u_=gm mpampmxeasucoc use anmpmxgmz u punch w ._ Lmaouoonmm um=m=< umm>gmz u mpnmuwxeme quohm .vp Langmuammumm pm3m3< pmm>gmz u anmpmxgms apgmmm .muopa snow mo cmmz_ mom “me pmm m.mm w.~m N.¢p mcwumswm mmm mFm com N.me ~.mm m.np copamo Rm m3 ma «.3 9% :2 3:28 mom Nuv Npm N.o¢ m.mm m.mp muPF=mcmm __m mom mom N.w¢ o.nm m.mp capom owe mac mmm e.om o.mm o._m co:_~mwo _mm o~m mam ~.m¢ u.mm u.m~ Lm_< moo Npm omm m.m¢ 5.5m o.¢~ _ogucou _mpoh anmpmxemz mpnmumxgoz pouch mpampmxemz mpnmgmxewz e m peach N mpgmm e m peach N apgmm a a a x ;\ .._.;\mop Foursmzo ta: .3 23a: :2“. .8 ages: . m.F.pnm_ .vpmwx Auwgnaz mmagzm .>ov copms co mpmuwsmzu Fmgzu~:o_gmm eo pummwu .m mpnm» Table 4. Effect of agricultural chemicals on tomato (cv. Campbell 721) yield, 1971. 18 Number of Fruit Height of Fruit " All means are nonsignificant at the Range Test. . Chemical x 103/ha. q/ha Marketable 2 Marketable Marketable and Matgre Marketable and Mature Green Green Diazinon 309 493 562 824 Captan 308 539 532 857 Carbaryl 299 494 539 854 Alar 295 500 518 817 Bensulide 278 486 512 823 Solan 274 507 502 855 Control 264 537 473 755 Simazine 206 393 385 593 1Mean of four plots. 2September 13-October 6. :September 13-0ctober 7. 0.05 level using Duncan's Multiple 19 m Solan, carbaryl, bensulide, simazine, alar and diazinon did not significantly influence green bean yield although they tended to reduce it slightly (Table 5). Zacchini squash Dinoseb application increased vine weight by 24%, number of squash by 29%, and weight of squash by 32%, but the increases were not signifi- cant. Trifluralin and simazine reduced vine weight by 15% and 33%. Each reduced the fruit weight by 24%. Neither greatly influenced.the.number of fruit harvested (Table 6). Effect on composition of tomato and melon leaves Nutrient analysis of tomato and melon leaves indicated relatively little influence of these chemicals on concentration of P, K, Na, Ca, Mg, Fe, B, Zn, and Al. Simazine increased the nitrogen and copper concentra- tion insignificantly in tomato leaves and significantly increased nitrogen and copper concentration in melon leaves (Table 7). The increased concen- tration seemed to be associated with reduced vigor and size of plants. Pesticide Effects on Vegetable Plants in 1972 The effects of four herbicides and one systemic insecticide on growth of beans, tomatoes, and muskmelons under field conditions were examined during the summer of 1972. There were significant differences in yield related to the treatments. 20 Table 5. Effect of agrigultural chemicals on green bean (cv. Provider) yield, 1971.1- Chemical - Kg/1.22 m. Rows Captan 4.52 Control 4.42 Solan 4.20 Carbaryl 3.76 Bensulide 3.72 Simazine 3.67 Diazinon 3.53 Alar 3.25 IMean of four plots. 2All means are nonsignificant at the 0.05 level using Duncan's Multiple Range Test. 21 Table 6. The effect of dgnoseb, trifluralin, and simazine on Zucchini squash, 1971.1- Number of Weight of Chemical squash squash A Vine weight (No x 103/ha) (Kg/ha) (Kg/ha) Dinbseb 100.1a 856a 493a Control 78.0a 647a 397ab Simazine 77.0a 502a 266 b Trifluralin 74.8a 501a 399ab 1Means of two plots. 2Those means followed by the same letter are not significant at the 0.05 level by Duncan's Multiple Range Test. 22 Table 7. Effects Of agricultural.chemical§ on mineral concentration in . v tomato and melon leaves, 1971. Tomato Melon Chemical' % NwF' ppm % N . ppm Cu Cu Captan 3.71a 5.94a 3.55bc 3.81b Simazine 3.53a 7.70a 4.21a 9.82a Control 3.46a 4.17a 3.57bc 4.86b Alar 3.45a 4.52a 3.45bc 5.91ab Carbaryl 3.43a 6.67a 3.29t 5.22b Bensulide 3.40a 4.19a 3.39bc 6.46ab Solan 3.40a 6.31a 3.73b 2.42b Diazinon 3.34a 4.17a 3.55bc 3.63b 1Mean of four plots. Means followed by the same letter are not significant at the 0.05 level by Duncan's Multiple Range Test. 2 23 TREATMENT EFFECTS ON MUSKMELON Early yield of melons Observations of vine growth on June 30 indicated occasional small necrotic spots on leaves of muskmelon plants treated with dinoseb. Later observations on July 9 indicated that necrotic spots were prevalent on plants treated with higher levels of dinoseb. A slight stunting of vine growth was also observed. Naptalam was associated with slight marginal chlorosis of leaves. Observations on July 17 indicated little difference in vine growth for any of the treatments. The data in Table 8 indicated that all chemicals, on averages of the three rates, tended to increase both marketable and total yield of melons that were harvested before September 13. Both number and weight of early marketable melons were increased significantly by more than two- fold by the application of the systemic insecticide disulfoton. The other treatments tended to increase yield although not significantly at the 0.05 level. Dinoseb was associated with 65% increase in number of melons and 62% increase in weight. Trifluralin treatment was related to 40% increase number of melons and 36% increase of weight. Average weights of fruit among the three treatments were not significantly different. The herbicide naptalam was associated with increased number and weight of early marketable melons by 56 and 57%, respectively. Bensulide was associated to a 48% increase of fruit number and 57% increase of weight, or an increase of 120 grams per melon (Table 8A). The chemicals had similar effects on the total production of early fruit, including marketable and nonmarketable (Table BB). Again, only 24 Table 8. The effect of pegticides on early yield of melon (cv. Burpee Hybrid), 1972. ’ . Average Chemical Number; Weight melon wt 3 (% 0f (% Of (No x 10 /ha) control) (q/ha) control) (Kg/melon) A. Early marketable melon yield-(September-S-lg). Disulfoton 11.09a 227 l46.la 217 1.32 b Dinoseb 8.05ab 165 108.8ab 162 1.35 b Naptalam 7.61 b 156 105.3ab 157 1.39ab Bensulide 7.18 b 148 105.8ab 157 1.49a Trifluralin 6.85 b 140 91.3 b 136 1.32 b Control 4.89 b 100 67.2 b 100 1.37ab B. Early total yields3 (September 5-12).. Disulfoton ‘ 13.9a 267 173.7a 247 1.25 b Trifluralin 10.2a 196 124.3ab 177 1.21 b Dinoseb 9.6 b 185 122.8ab 175 1.28 b Naptalam 9.1 bc 175 121.3ab 173 l.33ab Bensulide 8.8 bc 169 126.1ab 186 1.39a Control 5.2 c 100 70.2 b 100 1.35ab 1Average of 3 levels of the chemical. 2Means followed by same letter are not significantly different at 0.05 level by Duncan's Multiple Range Test 3 Includes marketable and non-marketable melons. 25 disulfoton Significantly increased number and weight of melons. Disulfoton increased number of melons produced by 167% and weight by 147%. Application of trifluralin resulted in a significant 96% increase in number and insignificant 77% increase in weight. Other treatments tended to increase early yield although not significantly. Naptalam treatment was associated to a 75% of number of fruit and 73% increase of weight. Treatment with bensulide resulted in 69% in number of fruit and 86% increase in early total weight. Thus, bensulide is again related to a slight increase in average size of melon (Table BB). Table 9A indicates the effects of the three rates of each chemical on number of early marketable fruit. It is of interest to note that for each chemical, except trifluralin, the highest yield occurred at the lowest concentration. The lowest level of disulfoton (1.12 kg/ha) re- sulted in the most early melons. The various levels of trifluralin that were»applied had similar effects on number of melons. Results in Table 98 show how the different levels of each chemical affected early total yield. There seemed to exist a trend similar to the trend expressed for early marketable melons.l The largest yield for each chemical, except trifluralin, occurred at the lowest concentration. Again, the largest yield was associated with the lowest concentration of disulfoton. Trifluralin resulted in greatest increase in melon number at highest rate. Total yield of melons The chemicals affected both seasonal yield of marketable melons and total yield of marketable and nonmarketable melons (Table 10). 26 Table 9. The effect of three rates of five chemicals on early yield of melons (cv. Burpee Hybrid), 1972.1: v.— Chemical (Rates Number of melons Low Rate . Interm.3Rate rvHigh Ratei (kg/ha) (No x 103/ha) (No. x 16 /ha) (NojrlO3/ha) A. Early marketable yield (September 5712). Bensulide 3.4, 6.7, 13.5 9.45 ab 7.18 ab 4.89 b Trifluralin 0.6, 1.1, 1.7 6.85 ab 6.85 ab 6.85 ab Dinoseb 3.4, 6.7, 13.5 10.43 ab 6.85 ab 6.85 ab Disulfoton 1.1, 2.2, 4.5 12.39 a 11.42 ab 9.46 ab Naptalam 2.2, 4.5, 9.0 9.13 ab 6.20 ab 7.50 ab Control 4.89 b B. Early totalyield.3 Bensulide 3.4, 6.7, 13.5 10.44 ab 10.11 ab 5.87 b Trifluralin 0.6, 1.1, 1.7 10.11 ab 9.46 ab 11.09 ab Dinoseb 3.4, 6.7, 13.5 11.09 ab 8.81 b 8.81 b Disulfoton 1.1, 2.2, 4.5 16.96 a 12.72 ab 12.07 ab Naptalam 2.2, 4.5, 9.0 12.07 ab 6.85 b 8.48 b_ Control 5.22 b 1Mean of three plots. 2Means followed by same letter are not significant at 0.05 level by Duncan's Multiple Range Test. 3Includes marketable and unmarketable fruit. 27 Bensulide significantly increased the number of marketable melons by 45% and weight by 47%. A trend of increased yields seems to exist for the other chemicals.- Dinoseb, disulfoton, naptalam, and trifluralin were related to increases of melon number by 34%, 32%, 31%, and 22% and increases in weight by 28%, 31%, 33%, and 23% respectively (Table 10A). More significant differences were attained for total yield than was for the marketable yield. Disulfoton increased number of melons by 30% and weight by 40%. Bensulide significantly increased number of melons by 27% and to the weight by 32%. Trifluralin and naptalam treatment plots yielded 21% and 19% more fruit and the two treatments significantly increased weight by 28 and 27% (Table 108). The results in Table 12 indicate the influence of the different rates of chemicals on the total number of marketable melons produced. Largest increases in number of melons for bensulide, dinoseb, disulfoton, and naptalam treatments again was associated with lower concentrations. The lowest rate of dinoseb was associated with the largest yield attained, but higher rates reduced yield. The highest yield with trifluralin was attained at the intermediate concentration (Table 11A). The effect of the three different levels of each chemical on total melon yield is indicated in Table 118. The lower rates of dinoSeb, disulfoton, and naptalam were related to greatest increases in yield. As the concentration of each of these increased, the number of melons produced decreased. Slightly greater yields were attained at the medium concentration of bensulide than either lower or higher concentrations. The three levels of trifluralin differed little in their influence on yield. 28 Table 10. The effect of pesticides on total yield of melon (cv. Burpee Hybrid), 1972. .2 f firfi Average Chemical _. ___Number .. . Weight " melon wt. .3 (%0f (%Of (N03610 /ha) Control) (q/ha) Control) (Kg/melon) A. Total marketableyyield (September 5-25). Bensulide 18.9 a 145 257.2 a 147 1.36 a Dinoseb 17.5 a 134 223.4 ab 128 1.28 a Disulfoton 17.3 ab 132 228.4 ab 131 - 1.31 a Naptalam 17.1 ab 131 231.4 ab 133 1.35 a Trifluralin 15.9 ab 122 212.7 ab 123 1.35 a Control 13.0 b 100 174.5 b 100 1.34 a B. Totalgyield (September 5-25), Disulfoton 22.1 a 130 285.9 a 140 1.22 ab Bensulide 21.5 a 127 268.0 a 132- 1.32 a Trifluralin 20.5 ab 121 262.1 a 128 1.28 ab Naptalam 20.1 ab 119 260.0 a 127 1.29 ab Dinoseb 19.7 ab 116 242.2 ab 119 1.22 ab Control 17.0 b 100 204.3 b .100 1.21 b 1Average of three levels of chemical. 2Means followed by same letter are not significantly different at 0.05 level by Duncan's Multiple Range Test. 29 Table 11. Effect of three rates of application of five pesticides on total number of melons (cv. Burpee Hybrid), 1972.1:2 Chemical Rates ' Number of Melons Low Rate Interm. Rate High Rate (No x 103/ha) (No x 103/ha) (No x 103/ha) A. Total marketable number (September 5-25). ’ Bensulide 3.4, 6.7, 13.5 19.90 ab 18.59 ab 18.27 ab Trifluralin 0.6, 1.1, 1.7 16.31 ab 16.96 ab 14.35 ab Dinoseb 3.4, 6.7, 13.5 21.53 a 17.61 ab ‘ 13.37 b Disulfoton 1.1, 2.2, 4.5 17.61 ab 17.61 ab 16.63 ab Naptalam 2.2, 4.5, 9.0 20.55 ab 16.31 ab 14.35 ab Control 13.05 b. B. Total number of melons. Bensulide 3.4, 6.7, 13.5 22.18 abc 22.83 abc 19.57 abc Trifluralin 0.6, 1.1, 1.7 19.90 abc 20.88 abc 20.88 abc Dinoseb 3.4, 6.7, 13.5 23.16 ab 20.22 abc 15.66 c Disulfoton 1.1, 2.2, 4.5 23.81 ab 21.53 abc 20.88 abc Naptalam 2.2, 4.5, 9.0 24.14 a .19.57 abc 16.63 bc Control 16.96 bc 1Averageuof nine plots. 2Means followed by same letter are not significant at 0.05 level using Duncan's Multiple Range Test. 30 Figure 1 summarizes the results of the 1972 melon experiment. As indicated previously, all chemicals, and especially disulfoton, increased early marketable yield. It is evident from the figure that the chemical also increased the pr0portion of unmarketable melons. Trifluralin in- creased the percentage of nonmarketable melons to a much greater extent than the other chemicals. Disulfoton markedly increased early yield above those of the other treatments although the figure indicates that the chemical did not elevate later yield as much as the control. Bensulide seemed especially effective for increasing both early and later melon yields. TREATMENT EFFECTS ON TOMATOES Early growth and floral development Observations of tomato vine growth on June 30 indicated that all levels of naptalam resulted in epinasty and curling of younger leaves. Observations on July 9 indicated that the epinasty had persisted until that date. Observations at that time also indicated that disulfoton occasionally restricted young leaf growth. Later observations on July 17 indicated that naptalam caused stunting of vine growth and the production of more and larger tomato fruit on the first cluster. These tomatoes were observed to have developed more roughness and cracking on the shoulder of the fruit. Chemical treatments resulted in variations in the number of flowers produced and in yield of fruit. Measurements collected on August 10 indicated that disulfoton application resulted in a significant increase 31 Figure l. The influence of agricultural chemicals on the early and total weight of marketable and nonmarketable melons (Cucumis melo L. Burpee Hybrid), 1972. 32 Flat” | YIELD OF NEWS (CV. BURPEE YIELD (ODIN TA l8!" ECTARE) 280 260 240 220 1.0 160 140 llIlllIlIllllllllIlllllllllIllIIIIIIIIIIIIIIIllllllllllW IllllllllllllllIlllllllllllIIIIIIIIIIIIIIIIIIIIVIZI I '7 m HIV/IA S IIIIIIIIIIIIIIIIIIIIIIV/t \é ‘ lllllIlllIlllllllllllllllllllllllllllllllllllllllllllIIIIVIIA 100 E: g; .. e: :2 e: E- .. E; SE 3% E; .. e: es s; e; 2» es es es :2 5% E: SE :7 :T .. HYBRID), 1972 ‘V NONMAnanLE ="— unnxenau E EARLY T TOTAL llllllllIlllllllIlllllllllllllIIIIIIIIIIIIIIII” I7. I l Illllll III|||IIllIlIIllIllIIIIllllllllllllllIlllllllllllllllllllllllllllllllll’lll. q BENSULIOE TRI FLURALI N CONTROL OISLLFOI'ON NAPTALAM DINOSEB 33 in the number of flowers in the anthesis stage. Total flower and fruit on the plant were increased 23% by disulfoton while vine weight was reduced only 4% (Table 12). Observations on August 10, indicated that development of the largest number of flowers occurred at the highest concentration (4.48 kg/ha) of disulfoton. Flower numbers were increased by 84% at this concentration while vine weight was reduced by only 4% (Table 13). The intermediate level of disulfoton (2.24 kg/ha) resulted in 35% increase in flower number and a five percent increase in vine weight (Table 13). The application of the herbicide dinoseb only slightly influenced the number of flowers and fruit although vegetative growth was signifi- cantly reduced. The results in Table 12 indicated that naptalam treat- ment significantly reduced vegetative growth and flower and fruit number. An examination of the effects of the various chemical levels MI, MW- in Table 13 indicated that the higher concentrations of naptalam were responsible for the greatest reduction in flower number. Although the lowest concentration (2.24 kg/ha) reduced the vine weight by nearly 50%, more flowers per plant were produced, indicating a very large increase in number of flowers per unit of vine weight. The highest concentration (8.97 kg/ha) of naptalam resulted in a reduction of vine weight of more than 50% but with a corresponding decrease in flower number. The inter- mediate concentration (4.48 kg/ha) differed from the others since it resulted in slight reduction of flower number and vine weight. A later flower and fruit count on August 18 again indicated some treatment effect. The previous information had indicated that some 34 Table 12. The effect of pesticides on growth and flowering of tomato (cv. Jet Star) plants, August 10, 1972.1.2 Number of flower, Chemical .__Flower number fruits - - Vine wt. (No./ (% of (No./ (% of (Kg/ (% of plant) control) plant) control) plant) control) Disulfoton 245 a 150 310.1 a 123 3.52 a 965 Dinoseb 174 b 106 240.6 b 96 3.30 b 90 ContrOI 164 b 100 251.2 b 100 3.67 a 100 NaptaIam 127 b 77 133.4 C 53 2.90 c 79 1Average of 3 levels. 2Means followed by same letter are not significantly different at the 0.05 level by the Duncan's Multiple Range Test. 35 .ummh mmcmm «Fawupaz m.=mu:=o any »n Fm>m_ mo.o as» an pcmgmmewu apucmuwewcmmm yo: mew empump mean an umzoF—om_mcumzm .muopa mags» mo mmmgw> 2t: m:_.> :52: apamuasaach _ ,4. , 254 . «ae\mev cowumepcmocou seam um mmcw> ecu mgmzopu Lo cowuuznoca mung N._.N~m_ .o_ pm=m=< .Aaapm “we .>uv opmeop mo usmwmz w=_> use Lassa: Lmzopm co mpmumsmnu m>wm mo mwumg mmggp we muummmm mgh .m_ mpnmp 36 chemicals were related to an increased number of flower per plant and that most chemicals were related to increased number of flowers per unit vegetative weight. Thus, a count of number of clusters were included in measurements on August 18. Dinoseb and naptalam treatments resulted in significant reduction of number of flower clusters (Table 14) which seem in general, to be associated with a reduction in vine weight. Although naptalam application was related;ta a severe reduction of number of flower clusters, it was related to more than a'threeefold increase in the number of flowers per cluster at anthesis stage. Observations indicated that many of theseIflowers were uncharacteristically large and often fasciated with numerous stamens and petals. Numerous small flowers were observed but not counted because they were too small and poorly develOped to undergo anthesis. Although naptalam significantly reduced the number of flower clusters, the increased number of flowers per cluster resulted in an increased number of flowers per plants. The total number of flowers and fruit per plant were decreased indicating fewer set fruit on vines. Dinoseb caused reductions in vine weight and a similar reduction in number of flower clusters. Besides reducing the number of clusters, dinoseb reduced the number of flowers per cluster, resulting in fewer flowers per plant. Dinoseb treatment was also observed to be related to the production of more fasciated flowers, and to more small flowers that failed to develop. Although causing a very slight reduction in weight of tomato vine and flower clusters, disulfoton application resulted in 66% more flowers 37 Swank mmcmm m_awu_:z m.:muc:a an Pm>mp mo.o pm unmemmwwu apucmovmwcmwm po: men qume mswm xn umzoFFom mammzm .mmpmg wanna mo wmmgm>

“was; a gmzopd mgmzopu - _.mguam:~u. mFGUmEmzo F.Namp .mu=a_a team “we .>uv cameo» Lo agave: mcw> co use .qumzpo gmzoFL .uwagm .memzope mo Lenszc co mmumuwummq eo pumemm mch .vp mpnmh 38 per cluster and 43% more per plant. Disulfoton application was also observed to be associated with occurrence of more fasicated flowers. Observation indicated that besides resulting in more fasicated flowers, dinoseb and naptalam seem to cause more fasicated flower stems. Flower clusters were often observed to be large with a fasicated pedical arising from the cluster. Also, the infloresences were large and more polychotomous (Figure 2A). These three chemicals were also associated with occurrence of more seedless fruit on the first two clusters (Figure 28). Fruit yield The treatments also affected fruit yield. All treatments were re- lated to an increased number and weight of early marketable tomatoes. Naptalam increased the number of fruit by 26% and significantly in- creased the fruit weight by 78%, thus causing large early fruit (Table 15A). It was previously shown that this was associated with a reduction in vine growth. Results in Table 16A indicate that weight was signifi- cantly increased at the intermediate rate (4.48 kg/ha) of naptalam and severely reduced in yield at the high level (8.97 kg/ha). Treatment effects of total marketable, varied more widely than early yield. Naptalam significantly reduced the number and weight of fruit harvested (Table 158). Results indicate the greatest reduction occurred at the highest concentration (Table 168). Bensulide, dinoseb, and trifluralin very slightly increased the number or weight of total marketable fruit (Table 158). Largest yield Figure 2. 39 The effect of agricultural chemicals on flowering and fruiting of tomatoes (Lycopersicon esculentum L. cv. Jet Star), 1972. A. Fasciated flowers of plants treated with 2.2 kg/ha of naptalam. B. Seedless fruit of plants treated with disulfoton (below) and seeded fruit (abbve) of control plants. 4O FIGURE 2' 41 Table 15. The effect of peitgcides on yield of tomato fruit (cv. Jet Star), 1972. u Chemical .. Number Weight (NO3 x (% Of (% Of 10 lha) control) (q/ha) control) A. Yield of early marketable.tomatoes,(August 5-23, 1972). Dinoseb 21.4 a 151 28.3 ab 144 Disulfoton 20.8 ab 147 27.3 ab 139 Bensulide 20.5 ab 145 26.7 ab 136 Naptalam 17.9 ab 126 35.0 a 178 Trifluralin 17.5 ab 124 22.8 b 116 Control 14.1 b 100 19.6 b 100 8. Yield of total marketable fruit (August 5-September 6,‘1972). Bensulide 100.5 a 105 173.2 a 96 Dinoseb 98.5 a' 103 182.9 a 101 Trifluralin 97.9 a 102 171.2 a 95 Control 95.7 a - 180.5 a 100 Disulfoton 83.6 a 87 150.5 a 83 Naptalam 21.3 b 22 45.8 b 25 C. Total biological yield of tomatoes. Chemical Kg/ha % of Control Control 912 a 100 Disulfoton 874 ab 96 Bensulide 854 a 94 Trifluralin 844 a 93 Dinoseb 788 a 86 Naptalam 254 b 27 1Average of nine plots. 2Means followed by same letter are not significantly different at 0.05 level by Duncan's Multiple Range Test. 42 Table 16. The effect of three rates of fivg chemicals on yield of tomatoes (cv. Jet Star), 1972.1: A Chemical ;_; Rate __ Low Rate . Interm. Rate High Rate (kg/ha) (q/ha) (q/ha) (q/ha) A. Early marketable yield. Naptalam 2.2, 4.5, 9.0 32.4 b 59 7 a 12.9 c Disulfoton 1.1, 2.2, 4.5 31.0 b 33.2 b 17.7 bc Dinoseb 3.4, 6.7, 13.5 31.2 b 31.6 b 22.1 bc Bensulide 3.4, 6.7, 13.5 24.5 be 30.5 bc 25.2 bc Trifluralin 0.6, 1.1, 1.7 20.6 bc ‘ 24.2 bc 23.7 bc Control 19.6 bc 8. Total marketable yield. Dinoseb , 3.4, 6.7, 13.5 204.7 a 241.7 a 102.7 a Disulfoton 1.1, 2.2, 4.5 153.1 a 191.5 a 106.9 a Trifluralin 0.6, 1.1, 1.8 179.0 a 170.5 a 164.2 a Bensulide 3.4, 6.7, 13.5 173.3 a’ 177.2 a 171.0 a Control 180.5 a . Naptalam 2 2, 4.5, 9.0 36.0 b 86.8 ab 14.6 b C. Biological yield. Trifluralin 0.6, 1.1, 1.8 820 a 944 a 769 a Disulfoton 1.1, 2.2, 4.5 784 a 942 a 895 a Bensulide 3.4, 6.7, 13.5 869 a 901 a 792 a Dinoseb 3.4, 6.7, 13.5 809 a 850 a 706 a Naptalam 2.2, 4.5, 9.0 410 a 234.a 119 a Control 912 a 1Average of nine plots 2Means followed by same letter are not significantly different at 0.05 level by Duncan's Multiple Range Test. 43 did occur at the intermediate (4.48 kg/ha) and lowest rate (2.24 kg/ha) of dinoseb. Disulfoton reduced weight by 17% with the greatest reduc- tion occurring at the highest level (4.48 kg/ha). The intermediate level (2.24 kg/ha) of the treatment yielded nearly 80% more fruit than the highest level (Table 168). All other treatments tended to reduce the yield; naptalam signifi- cantly reduced the biological yield of tomatoes (Table 156). The inter- mediate concentration of each chemical except naptalam resulted in the greatest yield for each chemical. The intermediate level of trifluralin (1.12 kg/ha) and disulfoton (2.24 kg/ha) resulted in yields slightly greater than the control. Figure 3 summarizes the marketable yield re- sults of the 1972 tomato experiment. It illustrates that all treatments were associated with slightly increased early yields. Naptalam especially increased early yield and decreased later yield. CHEMICAL TREATMENT ON BEANS Bean leaves of plants treated with dinoseb were observed on June 30, 1972 to have necrotic spots. Naptalam was associated with epinasty of leaves. Later observation on July 9 associated naptalam with the occur- rence of uncharacteristic salvoid-type leaves. These symptoms persisted through observations on July 17. Naptalam treated plants were also grow- ing more slowly. Differences in final stand and yield were associated with treatment. Final stand was increased 50% by trifluralin and increased significantly 84% by disulfoton (Table 17A). These two chemicals were applied two weeks after seeding germination had occurred. 44 Figure 3. The influence of agricultural chemicals on early and total weight of marketable tomatoes (Lycopersicon esculentum L. Jet Star), 1972. 46 Table 17. Effect of two rates of five pesticides on green beans (cv. Provider), 1972.1 _f fir—v . Chemical ' ;_ Rate __I _ _Low Rate High Rate Average A. Plant Number (x 103)/ha.' Disulfoton 1.1, 2.2, 414 124 a 160 a 142 a Trifluralin 0.6, 1.1, 1.7 121 a 111 a 116 ab Naptalam 2.2, 4.5, 9.0 106 a 103 a 105 bc Bensulide 3.4, 6.7, 13.5 102 a 87 a 95 bc Dinoseb 3.4, 6.7, 13.5 102 a 81.a 92 be Control 77 a 77 c 8. Yield ha . Trifluralin 0.6, 1.1, 1.7 205.1 a - 167.1 a 186.1 a Disulfoton 1.1, 2.2, 4.5 193.1 a 172.0 a 182.5 ab Bensulide 3.4, 6.7, 13.5 195.8 a 130.2 a 163.0 ab Dinoseb 3.4, 6.7, 13.5 182.7 a 129.7 a 155.7 ab Control 147.2a 147.2 b Naptalam 2.2, 4.5, 9.0 79.2 a 85.2 a 82.2 c C. Vine Height (q/ha). Bensulide 3.4, 6.7, 13.5 97.1 a 90.1 a 93.6 a Disulfoton 1.1, 2.2, 4.5 98.2 a 87.9 a 93.0 a Trifluralin 0.6, 1.1, 1.7 96.6 a 89.0 a 92.8 a Naptalam 2.2, 4.5, 9.0 102.5 a 78.1 a 90.3 a Control 89.5 a 89.5 ab Dinoseb 3.4, 6.7, 13.5 91.7 a 64.5 a 78.1 a 1Average of nine plots. 2Means followed by the same letter are not significantly different at the 0.05 level by Duncan's Multiple Range Test. 47 Naptalam, bensulide, and dinoseb applications slightly increased stand of plants at both concentrations. The lower level of all treat- ments except disulfoton resulted in higher plant stand. Naptalam significantly reduced the bean yields. Trifluralin sig- nificantly increased yield and disulfoton increased yield by over 20%. Bensulide and dinoseb treatments were related to insignificant increases in yield. All chemicals except for naptalam, were associated with greater increased yield at the lower level at which each was applied. This trend of greatest yield at lowest concentration seemed to corre- spond to the final stand of plants, with exception of disulfoton (Table 178). Only dinoseb caused significant reduction in vine weight, which was apparently due to toxicity at the higher concentration. The other treatments only slightly influenced vine weight. The slight effect on total vine weight and the increase in plant number associated with disulfoton, trifluralin, bensulide, and naptalam, indicates these plants were smaller in size than the control. For each chemical treatment, the greater plant weight occurred at the lower concentration, and in each case this weight was slightly more than the control. Thus, the insecticide disulfoton and the herbicide trifluralin seem to be effective for promoting plant stand and increased yield. GENERAL DISCUSSION The use of herbicides in these experiments influence crop growth in ways other than elimination of competitive weeds. The chemical treatments of 1971 did not cause significant differences in yield. All chemicals in 1971, with the exception of captan, resulted in a reduced early marketable and slight increase in total yield of melons. The reduced early yield of simazine was contributed to observed vine damage to both melons and tomatoes. ‘Many of the Chemicals seem to have shifted the harvest peak of tomatoes to earlier in the season. All chemicals, with the exception of simazine, resulted in increased yield of tomatoes and later a slight reduction in total marketable and mature green yield. The trend toward induced earliness existed in 1972. All of the chemicals that-were applied (disulfoton, dinoseb, naptalam, bensulide, and trifluralin) increased the early yield of melons, disulfoton doing so significantly. All treatments also increased the early marketable yield of tomatoes, dinoseb increasing number of fruit significantly and naptalam increasing weight significantly. The yield trend of 1972 differed from that of 1971 since the treat- ments in 1972 generally produced more early fruit and continued to out- produce the control, resulting in greater total yields. Disulfoton, bensulide, trifluralin, and naptalam significantly increased total melon 48 49 weight. Bensulide seems to be especially beneficial to increase both size and number of melons. The total marketable yield and total yield of tomatoes in 1972 was not greatly influenced by chemical, except for a severe reduction by naptalam. All treatments were associated with higher early yields than the control. This agrees with a report by Rogers (48) that other herbicides, solan at 4 lbs/A and simazine at l lb/A on heavy clay soil caused more early tomato fruit than other herbicides or hoed check._ The trend of increased early yields can be especially important to those who strive to produce crops before the market supply peaks. Produce prices are usually higher when the supply of fruit is limited. Disulfoton appears to be especially effective for this purpose on melons, although not labeled for that crop. As stated before, all chemicals used in 1972 resulted in increased total melon yield, while this was not true in 1971. This is again important to the producer. The early part of the growing season in 1972 was cool and not desirable for melon growth. Average Michigan melon yields fell from 75 th/A in 1971 to 65 th/A in 1972 with prices, increasing from $7.92 in 1971 to $10.30 th in 1972 (18). Producers can be especially benefited by higher yields during stress growing seasons. Herbicides treatments may be of more value in influencing crop growth during suboptimal than optimum growing conditions. Bensulide, a herbicide that is labeled for use on melon, was used both years and appeared more beneficial in 1972. 50 This study did not ascertain the factors influencing the difference in yields between the two years or why more significant results occurred in 1972. The differences may be associated with timing of application. The 1971 treatments were applied the same day as transplanting, while the 1972 treatments were applied two or three weeks after transplanting. The difference in stage of development may have influenced the activity of the pesticide. For example, the roots of the transplants may have been EFT? I better established at the time of treatment application in 1972 than in 1971. This would influence the plant's ability to absorb and transport the chemical. Thus, stage of physiological development at time of appli- } cation may have influenced the activities. A second possible explanation is that a chemical interaction may have existed in 1972 and not in 1971. ‘Amitrole T had been applied to soil at 2.24 kg/ha in late April of 1972. Thomson (55) describes the chemical as having an average persistance of two to four weeks in soil. The spring and early summer were cool, therefore, the chemical may have persisted longer. Yet, transplanting did not occur until about six weeks after Amitrole T application and treatments were applied two months later. Amitrole T injury symptoms were not observed on any plants. It is, therefore, unlikely that the Amitrole T persisted long enough in soil for an interaction with the treatments to occur. A third possible explanation for the variation between years may be due to environmental factors. There are many that may be considered, but one evident difference is the variation in the temperature pattern of the early growing season. Early yields were increased both years, but more 51 significantly in 1972. Plantings were established earlier in 1972 and experienced cooler growing conditions. Figure 4 indicates that June of 1972 averaged 9°F cooler than June 1971, and nearly 6°F cooler than the 30 year average. The chemicals may have exerted more influence under cooler conditions. The length of growing season probably influenced the pesticides' effect on total yield. As indicated before, chemicals increased early melon yield in 1972 although not in 1971. This was probably related to growing conditions and length of growing season. The harvest period of 1971 was longer than that of 1972, and about twice the number of melons were harvested. The control plants in the 1971 experiment tended to begin producing later than the chemical treatments, although eventually sure passing most treatments. The following year, all treatments were asSoci- ated with increase, early yield, and with increased total yields. Perhaps when harvest periods are shorter and yields lower, the earliness trends continue through the season causing increased total yield. The insecti- cide disulfoton had caused the greatest early melon production, yet the control out-produces it during the latter part of the harvest. Because Of the elevated early production, disulfoton resulted in greater overall yield than the control. If the season had been longer, the control may have out-yielded the disulfoton treatment. I The results indicated significant yield increases were attained from dinoseb treatment of zucchini squash in 1971 and from several treat- ments on muskmelons, tomatoes, and beans in 1972. The observed differences indicate that the chemicals were influencing plant growth in some manner. 52 .mmmcm>m Lam» om m use .mkm— ._~o_ Low mesa eo,nuaoe any uom.mg=pmcmasmp xpspcoe some as» ompm.ucm.mczpacma5mula_wmu came ecu we cemwcmasou .e acumen 53 >< 002. 30. 0.; eds ulna w¢3~