vrfim | . “ x V . *‘\M 1‘ ‘, b H “:s ‘\ ‘ ‘ “ll‘w i u | l ‘ H y H " l H H W N l THE EFFECT OF 2,. 4-DICHLOROPHENOXYACETIC ACID, 3~AM§NO-L 2, 4-TRJAZOLE AND 2,. 2-:DECHLOROPROPEONM ACiD ON GROWTH QF QA‘FS, S'D‘X’BEANS AND CORN, WWH SPECIJ3.L REFEREMQE TO MORNQNG VERSUS EVENIN‘S APPLICATION 'fhesis "far 3M Degree: 6:! M. S. MECHIQAH 2"?ATE UMEVERSETY F’emiw! Emanue? Janksm 1959 THE EFFECT OF 2,4-DICHIDROPHENOXYACETIC ACID, 3-AMINO-1,2,4-TRIAZOLE AND 2,2-DICHMOPROPIONIC ACID ON GROWTH OF OATS, SOYBEANS AND CORN, WITH SPECIAL REFERENCE TO MORNING VERSUS EVENING APPLICATIONS by PERCIVAL EMANUEL JACKSON A THESIS Submitted to the College of Agriculture of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Farm Craps 1959 ABSTRACT 2,4-Dichlor0phenoxyacetic acid (2,4-D) at l and 2 pounds per acre stimulated vegetative growth of oats. Stimulation of growth was greater from.evening than from morning spraying. 3-Amino-l,2,4-triazole (Amitrol) and 2,2-Dichloroproprionic acid (Dalapon) reduced the length of panicle, number of panicles, number of kernels per panicle, and yield. In general, evening treatments with amitrol were more injurious than morning treatments, while the reverse of this was true for dalapon. The effect of amitrol on yields could be predicted from injuries observed soon after spraying. 2,4-D at 1/4 and 1/2 pounds per acre reduced the yields of soybeans. Evening treatments tended to be more injurious than morning treatments at the high rate of application as measured by maturity and yield. Both amitrol and dalapon reduced yields of soybeans at rates used in this experiment. In general, evening treatments were more injurious. Both chemicals reduced size of seed. 2,4-D applied to corn at 1 and 3 pounds per acre caused injury as shown by rolled leaves, crooked stalks and malformed brace roots. Evening applications were the most injurious. Evening applications of amitrol on corn showed more visual injury than morning applications. However, plants outgrew the injury. L1 ACKNOWLEDGMENT The author wishes to express his sincere appreciation to Professor Boyd R. Churchill, under whose guidance this investigation was conducted, and for his untiring assistance in the preparation of this manuscript. Expressions of gratitude go to Dr. S.T. Dexter for his inspiration and encouragement in the pursuance of the experiment, his constructive criticisms and unflinching cooperation in the preparation of this manu- script. Thanks are extended to Kalapatti M. Srinivasan, M.S., for advice on the collection and analysis of the data; to my house mates Andrew D. Dunbar and Horace F. Hamilton for their unsolicited help in the collection of samples; and to John H. Showers, Jr. of the Farm.Crops Laboratory, for providing additional help when experimental procedures demanded it. I owe a special debt of gratitude to my wife Pearline, who was a source of inspiration and encouragement throughout the entire program, and to Paula and Eda, our children, for their sustained loyalty and under- standing, not having seen Dad for the full duration of this investigation. "J LIST OF FIGURES Figure Page 1. Hood used to prevent drift ------------------------------ 9 2. Drift control - by hood --------------------------------- 9 3. Lodging of soybeans - morning application of 2,4-D ------ 26 4. Lodging of soybeans - evening application of 2,4-D ------ 26 5. Delayed maturity - morning applications of amitrol ------ 33 6. Delayed maturity - evening applications of amitrol ------ 33 7. Effects of 2,4-D on brace roots of corn ----------------- 36 8. Chlorosis - morning application of amitrol on corn ------ 39 9. Chlorosis - evening application of amitrol on corn ------ 39 W The discovery and synthesis of 2,h-DichlorOphenoxyacetic acid (2,4-D) and allied substances initiated an unprecedented era in the control of weeds by chemicals. The type of weed species, crops, stage of growth, time and mode of application, formulation of chemical employed, weather conditions and soil type considerably influence the action of these chemdcals, contri- buting to their success or failure. Users of chemicals often express contrasting views on the effectiveness of a given chemical on a particular crop applied at recommended rates. It is therefore obvious that factors other than the chemical itself are responsi- ble for the successful usage of these herbicides. Since these factors are often included in spray recommendations with no specific reference to time of day that applications are made, it is reasonable to assume that "time of day" may be a limiting factor. This is the hypothesis that led to this experiment to determine the effects, if any, of time of day upon the rate of absorption and translocation of herbicides by crops. The ability to control weeds without imparing crop yields has not always been easy. iHany investigators have directed their attention on the effect of 2,4-D and allied substances on crop yields, and particular attention seemed to have been paid to cats, soybeans and corn. Results have not always been consistent and both increase and reduction of yields have been reported. The rate, time of application, and stage at which the crop should be treated appear to be of paramount significance in terms of measuring success of weed control and in terms of crop yields. Only limited studies seem.to have been undertaken in this direction. 73 n , ' . \o' a r. . l- 4 b J ' A 4‘ .‘j . . J L, \ _I . . . . V’N REEIEH OF LITERATURE Mitchell and Brown (20) found that leaves in the dark responded more slowly to 2,4-D than did those in the light. They observed that 2,4-D growth stimulus was translocated only in the presence of light, indicating that the 'movement was associated with the products of photosynthesis, and the trans- location of organic food materials. Linder et a1 (18) obtained similar re- sults. Rohrbaugh and Rice (25) found that addition of sucrose to plants treated with 2,4-D in the dark increased the amount of translocation. Very marked stem.curvatures resulted when red kidney bean plants were treated and kept in bright light, while there was no reaction when plants were kept in a shaded location or in darkness (33). Tam.(30), working under Hawaiian conditions, stated that temperatures ranging from a minimum of 70° F to a maximum of 85° F through the larger percentage of days is highly favourable for the action of 2,4-D. Hammer and Tukey (13), Harth and Davis (19) and Kelly (17) have .11 shown that 2.4-1) sprays are more effective in warm weather, and the herbicidal effectiveness increases with high temperatures. Several investigators (l, 7, 10, 27, 32) have reported reduction of yields of eats from applications of 2,4-D at the 1/2 and 1 pound per acre rates. .Aldrich (1) reported that fertility levels influenced the effect of 2,4-D on yield, tillering, number of seeds per tiller and seed weight. He observed significant reduction in yield at high fertility levels, increased tillering and mean seed weight at high fertility levels, and that reductions in number of seeds per tiller were consistently associated with reductions in yields. Aldrich also noted that an increase in seed weight normally occurs with a reduction in number of seeds per tiller, providing fertility is adequate. .. '1 In addition to lower yields, Brown (5) reported injuries expressed in the form of stiffened, discolored foliage, onion leaf, enlarged nodes, twining of stems, panicles and spikelets, "side oats", uneven length of stem and weakened straw in oats. Grigsby and Churchill (12) stated that several varieties of oats sprayed when 4 - 6 inches in height did not show any evidence of injury to vegetative tissue from.2,4-D at 3/4, 1-1/2 and 2 lb. per acre rate. There.was also no reduction in yield. Derscheid et al (10) pointed out that applications of 2,4-D significantly decreased the average number of seeds per panicle, but the seed weights on treated plots were significantly higher than from.untreated plots. They noted an onion-like leaf effect. Leaves had definite onion-like appearance (32) and were not as numerous as in untreated plots. Plants were later in heading, shorter and had a tendency to lodge. Shaw, Hillard and Bernard (27) undertook a study at the Ohio State Exp. Station to determine the effect of 2,4-D on Clinton 59 oats when applied at 6 rates of application and nine stages of growth. They concluded that the pre-tiller, boot and early heading stages were clearly defined as the least tolerant stages while the full tiller, bloom and milk stages were the most tolerant stages in the life cycle response of oats to 2,4-D. Oats were found to be more sensitive to injury from.2,4-D than wheat and barley. Stahler (29) claimed that eats showed a definite retardation in flowering when treated with the higher rates of 2,4-D compounds, while Rice (22) observed no apparent differences in time of flowering or amount of flowering in any of the sprayed plants as compared with the controls. Stahler (29) and Wolfe et al (35) classified soybeans as being very sensitive to 2,4-D sprays. Soybeans were affected more quickly and to a J ’ \ I I n 1 .4 , r ~ I u l ) c -\ u , e . . r‘ greater extent when grown in nutrient solutions high in nitrogen than in those with a low nitrogen level (35). Weaver et a1 (34) found that 2,4-D applied at 1/2 pound per acre to soybeans 6 - 8 inches in height caused severe distortion of plants and retard growth, but plants later recover to produce normal yields of beans. Applications at later stages of growth reduced yields significantly. Floral and aerial structures were also affected.. It was pointed out by Rice (23) that there was greater absorption of 2,4-D by beans at a temperature series of 86 - 92° F than one of 79 - 82° F. He observed stemncurvatures in all plants in series 79 - 82 and 86 - 92° F while there was no curvature in series 46 - 58° F. Rohrbaugh and Rice (25) found that 2,4-D was not translocated out of destarched bean leaves in the dark unless sugar was added to the leaves. However, the application of a 101 sugar solu- tion resulted in stem,curvature and inhibition of trifoliate leaf blades. Fructose and glucose were found to be more effective than sucrose in augmenting the translocation of the growth regulator. Slife (28) experienced curling of leaves and bending of upper part of plant within 3 hours after spraying with 2,4-D. Injury increased in severity up to 48 hours after treatment, at which time recovery at the lower rates (1/16 and l/8 pound per acre) began. Hanson and Freeman (l4) reported a 10% reduction in hay yield from 1/16 and 1/8 pound per acre rates of 2,4-D on Habash soybeans. Root proliferation has been reported (6, I6, 21, 24) as one of the common 2,4-D injuries in corn. Buchholtz (6) observed greatest root injury when corn plants between 10 and 40 inches in height were treated, but others (3) have tentatively recommended spraying the plants at heights varying from 12 to 36 inches. Rodgers (24) noted considerable stalk bending from 2,4-D appli- cations to plants in the 6 - 11 leaf stage. He also found leaf rolling and 5 reduced yield to be noticeable injuries. Other investigators (11, 16, 31) reported that 2,4-D reduced yields in corn. Hoffman (16) reported a reduction in corn yield in one instance from the use of 1/2 pound of 2,4-D per acre and a 501 increase in growth in another instance when applied at the rate of 1 1/2 pounds per acre. He also observed varietal differences in brittleness when plants were treated with 2,4-D. Warren and Hernandez (31) and Rodgers (24) report reduction on yield of corn by use of 2,4-D; whereas Dearborn (9) reports an actual increase in the yield of corn and Havis and Sweet (15) report that no significant reduction in yield of corn was noted, even when corn plants were badly malformed by 2,4-D sprays. Ellis and Bullard (11), after experi- nenting on 18 varieties of sweet corn with 5 formulations of 2,4-D, indicated that there was no significant increase or decrease in number of marketable ears, yield or stand for any of the varieties tested. The maturity of varieties did not appear to be affected. Dalapon at rates as low as 4 and 6 pounds acid equivalent per acre effectively controlled heading of wild oats when applied from the seedling stage up to and including the fully tillered stage (2). There was no notice- able effect from any rate at the end of the first week, but two weeks after treatment, tip burning was noted on all plants and stunting was apparent. They also observed retardation in the elongation of the flowering stalk, leaving the panicle partially or completely enclosed in the boot at maturity. It was noted that dalapon increased tiller production even when applied after the plant had ceased normal tillering. Severity of damage and speed of kill are directly proportional to the concentration of dalapon (26). Santelman and‘flillard (26) placed plants in the dark before and after treatment and observed that the degree of kill of treated shoots compared to plants which . z a , U j j a V ’ \a a a O .. . n we a ) .. ‘ \ (‘1 . p . t . . fix _ 7 . a no. . x in I . 4 . «I e L J ._ . ‘. . .l _. . . .‘. I r: i . 4 t J 4 , . \ ‘ e 4 . '\ 6 had received no treatment was not affected. Danielson and Shuaaker (8) noted that dalapon produced necrotic areas on leaves of toaato by the second day following application. Necrotic areas on leaves were accompanied by marginal burns and a tendency for edges of leaves to curl under. New foliage bees-e chlorotic. Bondarenko and Willard (4) stated that the most striking effect of amitrol on plants is the loss of chlorophyll from the leaves within a week after treatment. Plants treated with amitrol first became yellow, then usually white and then turned brown and died. They indicated that if the initial dose of amitrol was low, some yellowed leaves regained their green color and con- tinued to grow. MATERIALS AND METHODS In this experiment, performed at East Lansing, Michigan, an attempt was made to determine the influence of time of day on the effect of appli- cations of 2,4-D, 3-Amino-l,2,4-triazole (Amitrol) and 2,2-Dichlor0propionic acid (Dalapon) on crop growth. Oats, soybeans and corn were the crops selected for the experiment. Garry oats were seeded on May 5, Chippewa soybeans were planted on May 20, and Michigan 350 hybrid corn was planted on May 27. Oats were drilled in 7 inch rows and the other two crops in 14 inch rows. Plots were 6.75 x 36 feet in size and treatments were randomized in four replications. Herbicides were applied between 6 and 7 a.m., between 1 and 2 p.m., and between 7 and 8 p.m. A "low" and a "high" rate of each chemical was used in all cases. An attempt was made to select a "low" rate which would be near the minim that would still show some crop injury. The actual rates in pounds of active ingredients per acre selected for the three crops are shown in Tab 1e 1. TABLE 1 Pounds per acre of active ingredients applied at low and high rates ours scams com cannon Low High Low High Low High 2.4-1) 1 2 1/4 112 1 3 Amitrol 2 4 2 4 l 2 Dalapon 2 4 1 2 ' 2 4 \V 3 ‘Methods ofIApplication: Plots were sprayed with a 6 foot boom mounted on a Farmal Cub tractor, delivering 35 gallons of spray per acre. Drift was controlled by the use of a hood (Fig. l and 2). Spraying equipments were thoroughly washed before changing chemicals and low rates preceded high rates in the case of each chemical. ' Stages of application for each crop were as follows: Oats - at the five leaf stage, sprayed June 9, (35 days after seeding); Soybeans - 5 to 6 inches in height, sprayed June 17, (28 days after planting); Corn - sprayed at the 7 to 9 leaf stage July 3, (31 days after planting). Collection of samples: Half square yard samples were harvested from the three center rows of each plot at ten day intervals up to 40 days, and the dry weights determined. Ten running feet of row of cats were harvested to determine yield, tillering, kernels per panicle, and length of panicles. Ten running feet of row of soybeans were harvested to determine yield. The yield data on oats and soybeans were converted into standard measurement as bushels per acre. Six plants from each plot in the first replication of oats and soybeans were dug up with a spade and the roots washed and examined for injury. 25 consecutive plants from each 2,4-D plot in the first two replications were examined for injury to brace roots in corn. Climatological data: Relative humidity and temperature were taken at time of spraying operations. LJ s i I '~ . ‘v ’ ‘ ‘ ‘g. ‘ fi : h :5 s.“ *v‘ 1 ' "- " ‘ "la , ‘ 2‘. q :2“! . y 5’ (a A. a p 9:. v. &1(.- 5‘."- ’ ' . - -‘ '- . ' ‘ k. . f _ . Q’é :11}: L {'7',’ Q ' ' X.‘ a? . 9;. ‘1" V O O' - m - I ~ I ' ‘ ‘v 'I . - 0‘? I l i . .‘ (_ ~ ~ '14.... ‘I ‘ ,. s I ‘1‘ ‘ __ .2 . LIA L‘ 1' .~’ IN”. “r. 3 F4 Fig.2 Shswi _~ tvenesso - controlling drift. late unsprayed row of soybean between 2,4-D and amitrol plots. .asbtoidrsd 5d: gnivqus :01 been finsmfiosjfia hood bns roaosrT I .g:: .3311b galilorjnoo at (I .313) insmdasjjs boofl 30 aasnsvljoeiis gniwoda S .31; .ajoiq lorjlms bus U-A.S nsewjed enssdgoa 30 wow bevswqenu 930d A d . I.'>.A ... . ... i a“ a mi .J ._ v n. _ .. 1)....é» ‘ .. .a «9% a .\ Us...” a.“ \ \N..wmae . . .o a ”.36: 10 RESULIS AND DISCUSSION OATS The dry matter accumulation at 10 day intervals following treatment 'with herbicides in comparison with the check and the final yield of grain in percent of the check are given in tables 2, 4 and 6. Tables 3, 5 and 7 show the final yields, number of panicles, grains per panicle, weight per 300 kernels, and other data pertinent to the con- dition at harvest time. Table 8 summarizes the data concerning accumulation of dry matter at the end of 40 days and grain yield in relation to rate and time of appli- cation of herbicides based on percentage of the check. Table 9 summarizes the data concerning number of panicles, number of kernels per panicle and weight of kernels in relation to yield for rates and times of application of herbicides based on percentage of the check. The relative humidities were 70, 40 and 72 percent at morning, noon and evening applications respectively. Temperatures at time of application were 72, 91 and 81° F for morning, noon and evening treatments. Neither relative humidity nor temperature showed any correlation with dry matter accumulation at the end of 40 days nor with final grain yields. 2,4-Dichlorophenoxyacetic Acid Injuries observed: Injury to early growth of the oats was difficult to observe. ‘Marginal and apical yellowing of lower leaves, stunting of plants and onion leaf effects were noted. There was no difference between time of flowering of the check.plants and plants sprayed with 2,4-D. Some lodging occurred on . . s . , . ‘ _ _ I .4 _ e v a - \ . ' r' i . J . 1 U ' i . ‘1 V V - ' ' 11 sprayed plots. It was the most severe on plots receiving the evening appli- cation and least in those with morning application. The severity of lodging increased with increased concentration. Some crooked panicles were observed. Effect on dry matter accumulation: 2,4-D stimulated growth as measured by the accumulation of dry'matter at the end of 40 days, regardless of the thee or rate of applications (Table 2). These differences varied from slight in the case of 1 pound rate of application made in the morning and at noon, to very substantial at the 2 pound rate applied in the evening. When the dry matter accumulation for each of the ten day intervals is totaled, the greatest increase resulted when 2,4-D was applied in the evening and was 11 percent for the 1 pound rate and 9 percent for the 2 pound rate. Effect on yield of grain: Lowest yields were obtained from plots where cats were sprayed in the ‘morning. Spraying at 2 pounds per acre resulted in lower yields than at 1 pound per acre. Oats sprayed in the morning at the higher rate produced approximately 10 bushels per acre less than oats not sprayed (Table 3). The early growth of oats was not in direct relation to final grain yields. Plots producing the lowest yield, produced slightly more dry matter in early growth (40 days after treatment) than untreated plots (Table 8). Length of panicle measured from the top to the bottom node of the head was not responsible for the yield differences. The treatment giving the lowest yield averaged the same panicle length as cats that were not sprayed. The number of kernels per panicle were not in agreement with yields. 2,4-D applied at the 1 pound rate tended to increase kernel weight but did not necessarily cause increased yields. The weight of kernels and the number of panicles per unit of row were inter-related in their effect on yield. —‘ ck; 12 Table 2. Effect of 2,4-D at low and high rates applied morning, noon and evening, on the accumulation of dry matter of oats har- vested at 10 day intervals up to 40 days following treatment. Rate Time of Days following treatment 1 of check Treatment lbs [A application 12 2_O_ §_9_ 9g W grams grams grams grams Check - - 136 233 341 329 100 2 , 4-D 1 morning 183 225 343 346 105 2 ,4-D l noon 132 223 298 336 102 2 ,4-D l evening 158 281 356 354 114 2 ,4-D 2 morning 125 220 344 362 110 2 ,4-D 2 noon 139 208 325 388 118 2,4-D 2 evening 118 228 313 473 144 13 Table 3. Effect of 2,4-D at low and high rates, applied morning, noon and evening, on length of panicles, number of panicles, number of kernels per panicle, weight of kernels and yields in bushels per acre of oats. Length* Number+ No. of weight Yield Rate Time of of kernels of 300 bu/ Z of per Treatment lbslA of day panicles panicles panicle kernels acre check Check - - 4.94 166 41 7.89 92.4 100 2,4-D 1 morning 4.98 156 40 8.22 87.8 95 2,4-D l evening 5.06 165 35 8.55 89.8 97 2,4-D 2 morning 4.96 159 39 7.89 82.8 90 2,4-D 2 noon 4.99 ~ 164 38 8.19 88.0 95 2,4-D 2 evening 5.12 175 41 7.83 96.4 104 * Distance between the first and the last node of the panicle in inches. 1+ Per 10 running feet randomly selected from center rows of plots. Difference between means needed for significance when using R.E. (range of equality) at 51 level is 23.9 bushels per acre, and at 1% level is 31.3 bushels per acre. {J 14 3-Amdno-l,2,4-triazole Injuries observed: Amitrol, unlike the odner herbicides, caused severe injuries to the vegetative phase of the crap. Injury developed rapidly, suggesting that amitrol was absorbed in larger amounts, more injurious or was translocated more rapidly than the other herbicides. Higher rates were definitely more injurious than lower rates irrespective of the time of application (Tables 5 and 7). All applications caused injury to plant growth. Injury varied from a brownish cast to a severe chlorotic condition and increased in severity to the third day after which a period of recovery occurred. In the early stages following treatment, the high rate applied in the morning showed greatest injury. However, as time progressed, evening treatment at the high rate became more injurious than all morning and noon applications. Plants recovered sooner from injuries resulting from morning than from noon and evening applications. Flowering was delayed. Effect on dry matter accumulation: Amitrol reduced the dry matter as measured 40 days after treatment, regardless of time or rate of application (Table 4). Dry matter was re- duced more by evening than by morning applications. Effect on yield of grain: All rates and times of application of amitrol reduced yields (Table 5). Reduction in yield was greater for evening than for morning applications. These differences were more pronounced at the lighter (2 pound) rate. Amitrol reduced the length of the panicles in all cases. Evening spraying produced the shortest panicles and morning treatments the longest panicles (except the untreated plots). High rates shortened the heads more | 7; A a 6019 ) I . “) ‘ ) , g ‘. r . "1 ) ‘ J ) . 3 a J . ) "3' 1 'J L , ) 7) 5‘ _ 3 _‘ ' 3 _ . , ' ‘ O . . j"! ‘ . q j , h. V .. "y W > a . . "J O . - >. ' « u ' , a» , J . ., :) ' ' ' 3 3 A. ) ._,‘ . ‘ I- r) , - ,1 ‘ ’ ;. s) '3 03-. \‘l .7 ') ., -_ -’ i" > n . s \ 4 o". \J I 15 Table 4. Effect of amitrol at low and high rates, applied morning, noon and evening, on the accumulation of dry matter of oats har- vested at 10 day intervals up to 40 days following treatment. Rate Time of Days fol lowing treatment 1 of check Treatment lbs/A application 10 20 30 40 at 40 days grams grams grams :r-sms Check - 136 233 341 329 100 Amitrol morning 97 162 253 250 76 Amitrol noon 111 157 202 294 ' 92 Amitrol evening 98 148 219 247 75 Amitrol morning 78 122 198 200 61 Amitrol noon 93 133 188 195 59 Amitrol evening 88 112 195 170 52 t) 16 Table 5. Effect of amitrol at low and high rates, applied morning, noon and evening on length of panicles, number of panicles, number of kernels per panicle, weight of kernels and yields in bushels per acre of oats. Length Number No. of weight Yield Rate Time of of kernels of 300 bu/ 1 of per Treatment lbslA of day panicles panicles panicle kernels acre check Check - 4.94 166 41 7.89 92.4 100 Amitrol morning 4.69 162 31 7.59 64.7 70 Amitrol noon 4.52 155 29 7.62 59.2 64 Amitrol evening 4.51 154 29 7.38 56.3 61 Amitrol morning 4.08 145 22 7.29 39.0 42 hitrol noon 4.22 150 21 7.23 38.4 42 Amitrol evening 3.97 146 19 7.38 35.9 39 Difference between means needed for significance when using R.E. (range of equality) at 5% level is 23.9 bushels per acre, and at 17. level is 31.3 bushels per acre. 17 than low rates. The number of panicles per unit area were reduced by all treatments. At the lower rates, evening applications were more injurious than morning treatments. Number of kernels per panicle were affected in the same way as length of panicles; the greatest reduction resulting from evening treatments. The weight per 300 kernels was reduced by all treat- ments. At the lighter rates of application, evening spraying was more in- jurious than morning treatments. Unlike 2,4-D and dalapon treatments, it was possible to predict the yields of amitrol treated plots based on injuries observed during the vegetative phase of the crop. Yields varied directly with degree of in- jury. This was also true for the accumulation of dry matter (Table 8). 2,2-Dichloroproprionic Acid Injuries observed: Dalapon treated plants did not show conspicuous injury in early growth. Some marginal and apical yellowing of lower leaves and stunting of plants were observed. Injury was more severe at high than at low rates. Some of the heads were partially enclosed in the boot at harvest time and some showed crooked panicles. In general, dalapon treatments produced peduncles that were shorter and thin with fewer spikelets. Effect on dry matter accumulation: Dalapon reduced the dry matter at the end of 40 days when applied in the morning and at noon, but did not when applied in the evening (Table 6). Effects on yields of grain: All treatments, regardless of time or rate of application, reduced yields more than low rates. At the low rates, evening applications were less in- jurious than noon, and noon less than morning treatments. Length of panicle, \J LO .0 k) ()3 \J3 ‘ - a T‘ble 6 o 18 Effect of dalapon at low and high rates, applied morning, noon and evening, on the accumulation of dry matter of eats har- vested at 10 day intervals up to 40 days following treatment. Treatment Check Dalapon Dalapon Dalapon Dalapon Dalapon Dalapon Time of application morning noon evening morning noon evening Days following treatment 10 grams 136 116 121 123 127 111 117 20 grams 233 218 219 199 188 128 185 30 grams 341 233 310 303 300 283 296 Z of check 40 at 40 days grams 329 100 293 89 298 91 344 105 287 87 267 81 321 98 1" (H 19 Table 7. Effect of dalapon at low and high rates, applied morning, noon and evening on length of panicles, number of panicles, number of kernels per panicle, weight of kernels and yields in bushels per acre of oats. Length Number No. of Weight Yield Rate Time of of kernels of 300 bu/ 1 of per Treatment lbslA of day panicles panicles panicle kernels acre check Check - - 4.94 166 41 7.89 92.4 100 Dalapon 2 morning 4.70 162 32 7.80 69.3 75 Dalapon 2 noon 5.00 164 35 7.71 76.1 82 Dalapon 2 evening 4.81 176 38 7.74 87.7 95 Dalapon 4 morning 4.33 145 35 7.35 63.9 69 Dalapon 4 noon 4.04 141 36 6.99 60.8 66 Dalapon 4 evening 4.44 162 35 6.96 66.8 72 Difference between means needed for significance when using R.E. (range of equality) at 5'1 level is 23.9 bushels per acre, and at 1‘1 level is 31.3 bushels per acre. .1- '7 I 1 IJ ‘ ' ‘, 7 \J . ._ fl . - I L . xii) n '0 _ _\ 20 Nu mm mm mod no am «a Ho me ha nu mm abandon an «n . ac nu Nd an #0 mm «a do ON on gonadl< ¢OA «ea um add me add no Nod ca odd mm «OH nu¢.N 33» J! 23» .2... Saw 5! 33» J! 33» .2... Sci J... hum hum hum mun hum but :3: :3 a»; :3 :3: :3 wowoo>u oooz mousse: moo-seeks 33339: no 8.3 hp oeooosuuoa .- xenon mo uooowom ea .euso mo omega dawn» one uoeluaomu woumw choc co menu-a.huo no eeueu mug: vow sea as consume one Henna-w .nne.u we uoemmm .m ego-a l 1llllIllllllllllIllIllllIlllllllIlIIllII-I-I-II-*=-=!-"'"““r7‘ ‘ "—" ’ _ 7!!!'7.4.- [ .2' 1.. Table 9. Relative importance of (A) number of panicles, (B) number of grains per panicle and (C) weight of individual grain and yield (% of check) finally obtained from oats treated with 2,4-D, amitrol and dalapon, High and low rates were used for each chemical and applications were made 6 - 7 a.m., 1 - 2 p.m. and 7 - 8 p.m.i; RATE 2 ,4-D RATE AMI TROL RATE DALAPON lbs/A TIMEOFDAY .5. g c_ Al 59 _B_(_:_ ABCYield lbs/A A g 9 fig 59 _1_3_§_ _;A_1_3_§__¥_i_e_1_gi_‘1bs/AC_4._ _1_3_ _g A]: 9.2 £9 ABCYield 1 morning 96 95 100 91 96 95 91 90 2 98 76 96 74 94 73 72 7O 2 93 73 99 76 97 77 75 75 1 noon 99 93 104 92 103 97 96 96 2 93 71 97 66 9O 69 64 64 2' 99 35 93 34 97 33 32 32 1 evening 105 100 99 105 104 99 104 104 2 93 71 94 66 87 67 62 61 2 106 93 93 99 104 91 96 95 2 morning 94 98 104 92 98 102 96 95 4 87 54 92 47 80 50 44 42 .4' 87 85 93 74 31 79 67 59 2 noon 101 95 103 96 104 98 99 98 4 9O 51 91 46 82 46 41 42 4 85 33 39 75 76 73 66 66 2 evening 99 85 108 84 107 92 91 97 4 88 46 94 4O 83 43 38 39 4 (I 93 85 88 83 86 75 74 72 IZ 22 number of panicles, and number of kernels per panicle were reduced by the treatments. Higher rates were more injurious than lower rates. At the low rate, evening applications were less injurious than morning treatments. Accumulation of dry matter.at the end of 40 days was directly related to yield of grain (Table 8). Length of panicle, number of panicles and number of grains per panicle were directly related to yield (Table 9). SOYBEANS The dry matter accumulation at 10 day intervals following treatment with the herbicides, in comparison with the check and the final yields in percent of the check are given in Tables 10, 12 and 14. Tables ll, 13 and 15 give data concerning total yield, size of seed and moisture content at time of harvest. Table 16 summarises the data concerning accumulation of dry matter and yield in relation to rate and time of application of herbicides. The relative humidities were 72, 56 and 58 percent at morning, noon and evening applications respectively. Temperatures at time of application were 54, 73 and 660 F for morning, noon and evening treatments. Neither relative humidity nor temperature showed any correlation with growth. 2,4-Dichlorophenoxyacetic Acid Injuries observed: 2,4-D was in every respect less damaging to the soybeans than either amitrol or dalapon. Plants were stunted in early growth and later leaves were crimped. As the plants advanced in maturity, there was profuse develop- ment of collar roots. This was more pronounced at the higher rate. Stems became crooked and lodging occurred by harvest time. More lodging occurred r) {J La ’) A \l . r. I . I x \ ,v . IJ my) nu; \J J. ,J 1 2 ~ .IJ 23 at the higher'rate but differences due to time of application could not be observed. ,At the lower rate, however, more'lodging occurred in plots sprayed in the evening, (Figures 3 and 4). Treated plants developed larger stems and showed splitting of the stems and peeling of the bark. Stems of treated plants were more woody and brittle. Effect on dry matter econ-nation: All treatments, regardless of time or rate of application reduced dry matter in growth up to 40 days following treatment (Table 10). With the exception of the first 10 day period, the'higher rate reduced dry matter more. Effect on yields of seed: All treatments reduced yields (Table 11). With one exception, the high rates reduced yields more than the low rate. Evening treatments reduced yields more than morning treatments at the higher rate of application (Table 16). Height of seed was not associated with yield. The high rate delayed maturity as indicated by the percent of dry matter at harvest time (Table 11). Podded beans contained less dry matter when plants were sprayed in the evening. 3-Amino-l , 2 ,4-triaaole Injuries observed: Amitrol caused more severe injuries than the other herbicides. In- juries developed rapidly. There was a general chlorosis followed by de- foliation. Greater injury resulted from the high rate although the low rate resulted in severe injury. As a result of a few showers late in the growth stage of the beans, re juvenatien of vegetative growth was initiated from the basal nodes of the plants. Consequently, plants that were totally defoliated \l .J 24 Table 10. Effect of 2.4-!) at low and high rates, applied morning, noon and evening, on the accumulation of dry matter of soybeans harvested at 10 day intervals up to 40 days following treatment. Rate Time of Days following treatment '7. of check Treatment lbs/A application 10 20 30 40 at 40 days grams grams gra- grams Check - - 45 103 174 301 100 2 ,4-D 1/4 morning 36 90 143 261 87 2 ,4-D 1/4 noon 38 89 149 312 104 2 , 44) 1 l4 evening 36 83 143 285 95 2,4-D 1/2 morning 35 75 134 244 81 2 ,4-D 1/2 noon 35 76 122 252 84 2,4-n 1/2 evening 36 74 131 234 78 Table 11. noon and evening, on percent dry matter at harvest, weight of seeds and yields in bushels per acre of soybeans. 25 Effect of 2,4-D at low and high rates, applied morning, Rate Treatment lbs/A Check - 2,4-D 1/4 2,4-D 1/4 2,4-D 1/4 2,4-D 1/2 2,4-n 1/2 2,4-D 1/2 Time of ‘7. dry mat.* weight of morning noon evening morning noon evening grams 83.0 83.6 82.2 84.9 79.0 76.1 75.9 grams 13.8 13.4 13.5 13.1 13.3 14.4 12.3 application at harvest 100 seeds bu.lA 62.8 47.9 53.5 48.4 52.8 49.2 42.1 Yield 2 of check 100 76 85 77 84 78 67 * Percent dry matter was determined on the basis of the moisture ‘ content of beans and pods. Difference between means needed for significance when using R.E. (range of equality) at 5% level is 18.3 bushels per acre, and at 1% level is 24.0 bushels per acre. 26 Fig. 3 Lodging in Chippewa soybeans from morning application of 2,4-D at 1/4 pound per acre. Picture taken 95 days follow- ing treatment. up" Fig. 4 Lodging in Chippewa soybeans from evening application ‘ b of 2,4-D at 1/4 pound per acre. Picture taken 95 days follow- ing treatment. as noijsoiqus gainrom mori ensedzoa sweqqidD at galgboJ C .313 -onIol 3136 69 main: erujoiq .sros rsq bnuoq ¢\I as fl-A.S 30 .JnstBSTJ gal noljsolqus gninsvs mori ansedgoa swsqqido at gaigbod a .313 ~woiioi 8286 8? node: erujokq .9133 rsq bnuoq A\I as U-¢,S io .Jnsmjsern gal 27 resumed growth and went on to produce a crop. Pods at harvest time were larger than pods from plants sprayed with dalapon, but smaller than those from plants sprayed with 2,4-D or unsprayed plants. Effect on dry matter accumulation: All treatments drastically reduced dry matter due to defoliation. This reduction was directly proportional to the rate used. Evening applications were more injurious than morning treatments (Table 12). Effect on yield of seed: All treatments reduced yields very drastically and in proportion to the amount of the chemical used. Lowest yields resulted from.plots sprayed at noon. Evening treatments resulted in yields slightly lower than morning treatments, (Table 13). Size of seed was reduced by all treatments. Podded seeds from noon applications were the most immature at harvest. At the lighter rate of application, the plants sprayed in the morning were more mature than plants sprayed at other times of the day (Figures 5 and 6). 2,2-Dichloroproprionic Acid Injuries observed: Action of dalapon on soybeans was slower than either 2,4-D or amitrol. Characteristic symptoms were stunting, and subsequent death of the apical buds. Leaves were rugose and showed chlorosis of the younger leaves. Later there was a profuse development of lateral stems, thus giving the plants a bushy appearance. Leaves developed a bronze color. Pods were smaller than pods of the other treatments. Effect on dry matter accumulation: (All treatments reduced the dry matter as measured at 40 days after treatment (Table 14). The high rate caused greater reduction in dry matter r. i J \_/ ,6“ ') , n I, 28 Table 12. Effect of amitrol at low and high rates, applied morning, noon and evening, on the accumulation of dry matter of soybeans at 10 day intervals up to 40 days following treatment. Rate Time of Days following treatment ‘1 of check Treatment lbs IA application .12 Q .3_O. Q at 40 days grams grams grams grams Check - - 45 103 174 301 100 Amitrol 2 morning 18 31 47 109 36 Amitrol 2 noon 11 17 19 42 14 Amitrol evening l3 17 25 66 22 Amitrol morning 11 22 25 48 16 Amitrol noon l3 19 15 20 7 Amitrol evening 9 13 11 26 9 29 Table 13. Effect of amitrol at low and high rates, applied morning, noon and evening, on percent of dry matter at harvest, weight of seeds and yields in bushels per acre of soybeans. Rate Time of 1 dry mat. Height of Yield Treatment lbslA application at harvest 100 seeds bu.lA I of check grams grams Check - - 83.0 13.8 62.8 100 Amdtrol 2 morning 56.3 12.6 40.2 64 Amdtrol 2 noon 42.1 12.1 29.5 47 Amitrol 2 evening' 43.1 12.2 38.4 61 ,Amitrol 4 morning 41.4 12.5 34.6 55 Amdtrol 4 noon 37.7 12.4 19.0 30 Amitrol 4 evening 40. 9 l3 .0 32 .4 52 Difference between means needed for significance when using R.E. (range of equality) at 51 level is 18.3 bushels per acre, and at 1% level is 24.0 bushels per acre. 30 Table 14. Effect of dalapon at low'and high rates, applied morning, noon and evening, on the accumulation of dry matter of soybeans at 10 day intervals up to 40 days following treatment. Treatment Check Dalapon Dalapon Dalapon Dalapon Dalapon Dalapon Time of morning evening _morning evening application 10 45 41 39 38 38 36 20 grams grams 103 100 99 82 80 65 30 grams 174 146 109 138 104 107 91 Days following treatment 1 of check 40 at 1.0 days ‘ grams 301 100 252 84 211 70 221 73 186 62 181 60 155 51 ~5- \,‘ 1;) J N .— 31 Table 15. Effect of dalapon at low and high rates, applied morning, noon and evening, on percent of dry matter at harvest, weight of seeds and yields in bushels per acre of soybeans. Rate Time of 1 Dry mat. weight of Yield Treatment lbslA application at harvest 100 seeds bu.[A Z of check grams grams Check - 83.0 13.8 62.8 100 Dalapon morning 70.7 12.4 31.7 50 Dalapon noon 61.4 11.7 31.1 50 Dalapon evening 65.0 11.7 33.6 54 Dalapon ‘morning 47.7 11.7 29.2 46 Dalapon noon 45.2 10.7 20.9 33 Dalapon evening 54.0 11.3 24.6 39 Difference between means needed for significance when using R.E. (range of equa1ity) at 51 level is 18.3 bushels per acre, and .r 12 level is 24.0 bushels per acre. 32 an an on mm mm oo on an 03 No on an m do «a on s so «H mm ea «o no as us no mu «a mm «as «a an em gammaqmmgaaaémmgfimm 33%.“ em nomads: on down: «a one.“ hue hum hum hum hum ham :3: >8 :3: :3 an; :3 woaoo>m oooz woqmuox noon—nosey .oouuwofimmw no no.3 .3 moo—"335 ea xoocu we nooowom a.“ .eowomhoe «o 30.1 use. use use-noon» wouuw ease o.» menus! hum so eoueu no.3 one tom um consume one Houuulw .91.».N we vacuum .ou sen—mu. 33 Fig.5 Effect of nitrol at 2 pounds per acre, applied in the morning, on the maturity of Chippewa soybeans. Picture taken 95 days following treatment. '91? Fig. 6 Effect of amitrol at 2 pounds per acre, applied in the evening, on the maturity of Chippewa soybeans. Picture taken 95 days following treatment. n1 bsiqus .9133 rsq ebnuoq S as Iorjims 10 339133 E .313 eruasiq .anssdgos swsqqidu 10 vjirujsm add no .gnlnrom 9d: .Jnsmjser gnlwolioi avsb 69 nsflsn n1 beliqqs .9138 Isq ebnuoq S 33 Iorjims 10 339113 6 .313 srujoiq .8nssdzoa sweqqidO io vjirujem and no .gninsvs 9d: .Jnsszsrj gniwolloi avsb 69 nsflej 34 than low rates and loss of dry matter was greater from evening than from morning spraying. Effect on yield of seed: Yields were reduced by all treatments (Table 15). At the higher rate of application, plots sprayed in the morning yielded more than plots sprayed in the evening. This is directly related to the amount of dry matter pro- duced in the early stages of growth (Table 16). Size of seed was reduced by all treatmentsggreater reduction resulting from the higher rates. Seed harvested from plants sprayed in the morning were somewhat larger than seed from plants sprayed in the evening. In general, size of seed was related to yield. Treatments made at noon delayed maturity the most. CORN The section on material and methods shows the rates of application of the 3 herbicides. However, due to rain following soon after the morning applications, replications l and 2 were resprayed the next day. Further complications were differences in soil fertility and the use of amounts of dalapon greater than the tolerance level for growth. Therefore, no data was collected from the plots treated with dalapon. Other data were confined to dry matter accumulation at 10 day intervals, brace root injury caused by 2,4-D and general observations of injury caused by amitrol. Tables 17 and 18 show the accumulations of dry matter under the herbicide treatments. The relative humidities were 77, 57 and 46 percent for morning, noon and evening appli:ations respectively. Temperatures were 54, 73 and 66°F for morning, noon and evening treatments. Neither relative humidity nor temperature showed any correlation with growth. 3’3 3 ., :7 V _ _ . _) 7' . U ' J ) .3 J _ .) ‘ ) _ , (1 35 Injuries observed: The usual injuries caused by 2,4-D developed within a few days. These included stom.curvatures, leaf rolling and later brace root malformations. In general, plots which received 2,4-D applications had small stems, narrower and shorter leaves than unsprayed plots. Respraying replications l and 2 led to no increased injury. There was practically no injury fromnmorning applications of 2,4-D to replications 3 and 4. Brace root injury was severe for all rates and times of applications of 2,4-D. This injury was least from morning and most from evening treatments (Figure 7). Aadtrol injury developed as a chlorotic condition within a few days. Greater injury resulted from.treatments made in the evening, (Figures 8 and 9). The plants outgrew this condition as in the case of oats. Tasseling was delayed and brace roots were smaller than the brace roots of unsprayed plots. Effect on dry matter accumulation: Dry matter was reduced by the application of 2,4-D, but the data were erratic, (Table 17). Data regarding dry matter produced by plants sprayed with amitrol were very erratic and could not be correlated with time or rate of application (Table 18). . . r|I II, all Im I O 7 .0 new 4 3 2 ... ¥D\P I 4. F"- m 'm h. I ‘ ..l e. VF.) \ r-‘ f. L , ,. ‘ \2 ,—\ x.» O Lb 37 Table 17. Effect of 2,4-D at low and high rates applied morning, noon and evening, on the accumulation of dry matter of corn at 10 day intervals up to 40 days following treatment. late Time of Days following treatment 1 of check Treatment lbslh application 10 20 30 40 at 40 days grams grans grams grams Check - - 158 333 840 908 100 2.4-1: 1 morning 121 342 636 800 93 2.4-1) 1 noon 156 313 863 931 103 2.4-1: 1 evening 138 221 454 704 78 2.4-0 3 morning 151 296 613 863 95 2.4-1) 3 noon 150 196 636 817 90 2,4-D 3 evening 139 300 613 863 95 38 Table 18. Effect of amitrol at low'and high rates, applied morning, noon and evening, on the accumulation of dry natter of corn at 10 day intervals up to 40 days following treatment. Rate Thee of Days following treataent 1 of check Treatment lbs IA application 19 32 32 42 at 40 days grams grams gran: grams Check - - 158 333 840 908 100 Andtrol norning 181 390 908 1113 123 Anitrol noon 175 255 613 936 103 Amitrol evening 149 305 545 817 90 Amitrol norning 111 216 523 704 78 Amitrol noon 104 356 681 1044 115 Amitrol evening 141 226 568 727 80 QC . ,-‘ r ' . .r ‘- - w . '. - ‘ ‘ .- . .1 ‘5‘; ‘4 , I '. . _' e a. s ‘ _" — . ' g . n 1 - w \l vrrr-v- ‘- nolssoaqus galore. vd beans: area at eleoroido 8 .313 .eraa req bnuoq I 33 Iornlna 10 noineeiiqqa gainsve vd beeuso are: at eieoroida Q .311 .oroa rsq bnuoq i an Iornims in Fig. 8 Chlorosis in corn caused by morning application of anitrol at 1 pound per acre. Fig. 9 Chlorosis in corn caused by evening application of amitrol at 1 pound per acre. 39 40 GENERAL OBSERVATIONS 2,4-D has been known to cause injury when applied to oats at the 2 and 3 leaf stage. Although these data indicate that 2,4-D actually stimu- lated the growth of oats, these rates would very likely have resulted in injury if spraying had been made earlier. Since stimulation of vegetative growth was greater when 2,4-D was applied in the evening, it seems reasonable to assume that injury also would have been greater from applications made at this time of day. Amitrol when applied to soybeans at 2 and 4 pounds per acre, as in this experiment, resulted in too much injury, regardless of tune of appli- cation. Rates of 1/2 and 1 pound per acre would have been more valuable in ‘measuring the effect of time of application. On corn, rates of application of amitrol higher than those used in this experiment probably would be more satisfactory for measuring differences. In the case of dalapon, rates used on soybeans and corn were too high. Rates of 1/2 and 1 pound per acre are suggested to show greater contrast in time of application. 1" ,— \ k) _j’) 41 SUMMARY The effect of rates and times of application of 2,4-D, amitrol and dalapon on oats, soybeans and corn are summarized. 1. 2. 3. 5. 6. 2,4-D at l and 2 pounds per acre stimulated vegetative growth. Stimu- lation was greater from evening than from.morning spraying. .Nmitrol and dalapon reduced the length of panicles, number of panicles, number of kernels per panicle and yield. In general, evening treat- ments with amitrol were more injurious than.morning treatments, while the reverse of this was true for dalapon. The effect of amitrol on yields could be predicted from injuries observed soon after spraying. 2,4-D at l/4 and l/2 pounds per acre reduced the yields of soybeans. Evening treatments tended to be more injurious than morning treatments at the high rate of application as measured by maturity and yield. Both amitrol and dalapon reduced yields of soybeans at rates used in this experiment. In general, evening treatments were more injurious. Both chemicals reduced size of seed. 2.4-9 applied to corn at l and 2 pounds per acre caused injury as shown by rolled leaves, crooked stalks and malformed brace roots. Evening applications were the most injurious. Evening applications of amitrol on corn showed more visual injury than ‘morning applications. However, plants outgrew the injury. \‘J l. 2. 3. 4. 5. 7. 8. 9. 10. 42 LITERATURE CITED Aldrich, Richard J. Effect of 2,4-D on the growth and yield of oats grown under three levels of fertility. Agron. Jour. 50: 145 - 148. 1948. Andersen, R.N. and Helgeson, E.A. Some effects of postemergence appli- cations of dalapon to wild oats. Need Jour. 4: 351 - 358. Oct. 1956. Bakke,.A.L. and Sylwester, E.P. As we fight weeds in 1948. Iowa Farm Sci. 2 (8) 7-8. 1948. Bondarenko, D.D. and Willard, C.J. Amino triazole appears to give control of Canada Thistle. Ohio Farm and Home Research 42: (305) 1947. Brown, D.A. Effect of 2,4-D on oats in 1952. (Abstract) Res. Kept. 9th. Ann. North Central Weed Control Conference. p. 74. Buchholts, K.P. Two years experience with 2,4-D in corn fields. Seed World 62: (3) 46. 1948. Burrows, V.D. and Olson, P.J. Reaction of oats to 2,4-D butyl ester when applied at 20 different stages of growth (Abstract) Res. Rept. 9th. Ann. North Central Weed Control Conference. p. 74. Danielson, L.L. and Schumacher,‘M.H. Experimental use of dalapon and natrin on certain transplanted vegetable crops. Proc. of 9th Ann. North- eastern Need Control Conference 97 - 103. 1955. Dearborn, C.H. Productivity of cultivated and uncultivated Golden Cross Bantam sweet corn weeded with post emergence sprays of 2,4-D. Proc. 3rd. Northeast States Need Control Conference pp. 69 - 72. Dearscheid, L.D., Straker, L.H. and tratochvil, D.E. Differential responses of oat varieties to 2,4-D. Amer; Jour. Agro. 45: (1) ll - 17. 1953. 11. 12. 13. 14. 15. l6. 17. 18. 19. 20. 43 Ellis, N.K. and Bullard, E.T. Varietal response of sweet corn to 2,4-D spray and the effect of different formulations of 2,4-D on yield. Proc. Amer. Soc. Hort. Sci. 51: 505 - 508. Grigsby, B.H. and Churchill, 8.0. Effects of 2,4-D on barley varieties. Michigan.Agri. Exp. Sta. Quart. Bul. 30: (4) 448 - 451. 1948. Hammer, C.L. and Tukey, H.B. Selective herbicidal action of midsummer and fall applications of 2,4-D. Bot. Gas. 106: 232 - 245. 1944. Hanson, J.R. and Freeman, J.F. Herbicidal tolerance of soybeans to post emergence sprays. (Abstract) Res. Rept. North Central Weed Control Conf. 8: 85 - 86. 1951. I Havis, J.F. and Sweet, R.D. The value of certain aromatic napthas and growth regulators as soil treatments for weed control in vegetables. Proc. Amer. Soc. Hort. Sci. 49: 325 - 331. 1947. Hoffman, Otto L. Effect of various 2,4-D formulations on crop plants. Proc. 3rd. Ann. Meeting of the North Central Need Control Conf. 95 - 97. 1946. Kelly, Sally. The effect of temperature on the susceptibility of plants to 2,4-D. Plant Phy. 24: 534 - 536. 1949. 'Linder, P.J., Brown, J.N. and Mitchell, J.N; Movements of externally applied phenoxy compounds in bean plants in relation to conditions favouring carbohydrates translocation. Bot. Gas. 110: 628 - 632. 1948. ‘Marth, P.C. and Davis, F.F. Relation of temperature to the selective herbicidal effect of 2,4-D. Bot. Gas. 106: 463 - 472. 1945. Michell, J.N. and Brown, J.N; ‘Movement of 2,4-D stimulus and its relation to the translocation of organic food materials in plants. Bot. Caz. 107: 393 - 407s 1946e \.j ‘J 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 44 Murray, Mary.A. and Whiting, Arc. Effect of 2,4-D on root development in young corn plants. Rice, Elroy L. Effect of various plant growth regulators on flowering in several crop plants. Bot. Gas. 112: 207 -'2l3. 1951. , Absorption and translocation of ammonium 2,4-D acetate by bean plants. Bot. Gas. 109: 301-314. 1948. Rodgers, E.J. Brittleness and response of corn to 2,4-D. Plant Phys. 27: (l) 153 - 172. Rohrbaugh, L.M. and Rice, E.L. Effect of applications of sugar on the translocation of sodium 2,4-D by bean plants in the dark. Bot. Gas. 111: 85 - 89. 1949. Santelman, P.N. and Willard, C.J. The absorption and translocation of dalapon. Proc. 9th Ann. Nertheastern‘Need Control Conf. 21 - 29. 1955. 'snsw,'w.c., Willard, C.J. and Bernard, 2.1. The effect of 2,4-D on wheat, oats, barley. Ohio Agr. Exp. Sta. Res. Bul. 761. April 1955. Slife, F.N. The effect of 2,4-D and several other herbicides on weeds and soybeans when applied as post emergence sprays. Need Jour. 4: (1) ° 61 - 68. 1956. Stahler, Len. Tolerance of crop plants to spray solutions of 2,4-D and other selective herbicides. Proc. North Central Need Control Conf. 2: 36 - 50. 1945. Tom, R.K. Cooperative herbicidal value of 2,4-D and 2,4,5-trich1oro- phenoxyecetic acid on some herbaceous weeds, shrubs and trees under Hawaiian conditions. Bot. Gax. 109: 194 - 203. 1947. warren, G.F. and Hernandez, T.P. Need control in certain vegetable crops with soil application of 2,4-D. Proc. Amer. Soc. Hort. Sci. 51: 515 - 525. 1948. ,. k; 1") ’) 32. 33. 34. 35. 45 Waywell, 0.0. The effect of herbicidal treatmerts on oats. Proc. 9th. Ann. Northeastern Weed Control Conf. 391 - 397. 1955. Weaver, R.d. and Derose, H.R. .Absorption and translocation of 2,4-D. Bot. Gas. 107: 509 - 521. 1946. Weaver, R.J., Swanson, C.P., Ennis, W.B. and Boyd, F.T. Effect of plant growth regulators in relation to stages of development of certain dicotyledonous plants. Bot. Gas. 107: 563 - 568. 1946. Wolfe, Dale E., Vermillion, Gertrude, Wallace, Arthur and Ahlgren, Gilbert H. Effect of 2,4-D on carbohydrate and nutrient element content and on rapidity of kill of soybean plants growing at different nitrogen levels. Bate Gus 112: 186 " 197s ('3 1) can? _U‘TV‘YH 1 USE cm _z,nwu3?i* . air—— MICHIGAN STATE UNIVERSITY LIB I III I | I III |RI|IIIES 3 1293 1306‘! 9890