'''''•V$*Q Division of Agricultural Scien c e s UNIVERSITY OF CALIFORNIA CALIFORNIA AGRICULTURAL EXPERIMENT STATION BULLETIN 828 Field tests over a three-year period confirmed that, under certain con- ditions, barban is effective against wild-oat competition in California barley and wheat crops. In varietal tolerance tests, all oat and rye varieties were killed (using supraoptimal rates of herbicides), but no barley or wheat varieties were reduced more than 45 per cent in tiller density at harvest. Barley was somewhat more tolerant than wheat. In laboratory tests, germination of barban-treated seed was rarely re- tarded — and then only by a few hours. No residue was detected. Re- sults in the limited studies with diallate indicated a narrower margin of selectivity and less predictability than with barban. Recommended conditions. . . . for the use of barban to control wild oats in California cereal crops: • wild oats — vigorous, in Wi-\o 2Va -leaf stages • crop— vigorous and competitive (not frost-injured, drought-stressed or underfertilized); in the 4-leaf stage or less • rate of herbicide — Va to V2 lb./acre; spray volume, 5 to 20 gal./acre • method of application— aircraft or ground rig to dry foliage, with pres- sures adequate to provide small droplets and good coverage; with low spray volume, usually 40 psi The authors: Chester L. Foy, formerly Associate Professor of Botany and Associate Botanist in the Experiment Station, Davis, is now Associate Professor of Plant Physiology, Virginia Polytechnic Institute, Blacksburg, Virginia. David E. Bayer is Lecturer in Botany and Assistant Botanist in the Experiment Station, Davis. NOVEMBER, 1966 Barban for Control of Wild Oats in Cereal Grains (Including Limited Studies with Diallate) THE FINDINGS 1 hese experiments were designed to study the tolerance of wheat, barley, oats and rye to barban (4-chloro-2-butynyl m-chlorocarbanilate), a postemergent her- bicide, and of wheat and barley to diallate (S-2,3-dichloroallyl N,N-diisopropylthiol- carbamate) a preemergent herbicide, and to determine the herbicidal selectivity of these compounds against wild oats infest- ing barley and wheat in California. The characteristic injury symptoms of both barban and diallate have been abun- dantly described in the literature since the initiation of these studies, 2 which further confirmed that symptoms were generally more pronounced at the higher (supra- optimal) rates (barban, 1 lb. /acre, and diallate, 3 lb./acre) than at the lower rates (barban, Va to V2 lb./acre and dial- late, 1 to 2 lb./acre). However, for both compounds, early crop injury symptoms did not necessarily result in reduced yields. Both barley and wheat showed an amaz- ing ability to recover. With barban, both crop and wild oats may be stunted initially — even at low rates. But if the wild oats are not killed, they are slowly repressed, whereas the crop recovers. Retarded wild oat plants frequently set fewer seeds. Final control of wild oats by barban is also strongly influenced by crop competi- tion, although it has been suggested that such control and competition (in barley) are independent, and simply additive. Not all advantages of successful herbi- cidal control of wild oats in cereal grains are realized during the year of treatment. Effective control prevents the set of viable seeds and can reduce wild oat infestation to a striking degree in the following year. Continued annual treatment progressively minimizes the problem to the point when herbicidal control on an annual basis might ultimately become unnecessary. 1 Submitted for publication May 14, 1965. 2 A list of general references appears at the end of this bulletin. The cover photo Fig. 1 . Barban-treated wheat field showing strips of wild oats skipped by sprayer. [3] For current recommendations and new developments in the use of se- lective herbicides in cereal grains and in other crops, consult the latest "University of California Weed Control Recommendations," obtain- able from your local Farm Advisor. When properly used, barban exhibits a marked and practically useful margin of selectivity (with few exceptions) on most common barley and wheat varieties grown in California, according to these studies. The rate of herbicide appears to be critical — as well as the timing of applications, spray volumes, and perhaps pressure as it affects spray droplet formation and dis- tribution. (Note recommendations on page 2.) Barban is intercepted and absorbed by the plants (both crop and wild oats) and is apparently translocated to a very slight extent into the meristematic areas. The herbicide acts primarily as a result of foliar uptake rather than root uptake, but selectivity cannot be explained on the basis of greater spray retention by wild oats than by barley or wheat plants. Such factors as environmental condi- tions, degree of initial toxicity, partial loss of stand, tillering capacity, and gen- eral recoverability appeared to vary among varieties. However, more critical studies correlated with final response and grain yield are necessary before predic- tions can be made with confidence. Where varietal differences were known or suspected to exist, wheat varieties ap- peared to be somewhat more susceptible to both barban and diallate than did barley. Age and vigor of both crop and wild oat plants at the time of treatment ap- peared to be important factors in the tolerance or susceptibility to barban. This agreed generally with previous re- search that the degree of wild oat control with barban is probably also a function of several factors — including dosage, vol- ume of diluent, fertility, stage of growth of weeds and crops, species and varietal differences. Treatment by aircraft as well as by ground sprayers proved effective; how- ever, the distribution patterns produced by aerial spraying were sometimes less uniform, resulting in streaks of variously maturing cereal in the same field. In rare instances, germination of seed from barban-treated cereals may have been retarded very slightly, reflecting the herbicidally-induced delay in maturity of the crop in areas receiving marginal dos- ages. Seed viability, however, was not af- fected by spraying the crop with barban; herbicide residues were not detected in the grain. Treatment with barban when wild oats are in slightly more advanced stages of Fig. 2. Wild oat plants showing (A) optimum growth stages for treatment with barban (lVfe to 214 leaves) and (B) less than optimum stages of growth (left, too early; right, too advanced). s ^E Fig. 3. Spraying with barban by ground rig and fixed-wing aircraft. (A, upper left) ground rig. Note fine spray which is necessary for best results. Small orifice nozzles (sizes 650067 or 730077) at 45 psi or more will provide good coverage with small droplets. (B, upper right) note angle of ground-rig nozzle adjustment to achieve better coverage of leaves of wild oats in the 2-leaf stage. (C, right) good coverage with fine mist using low volume of spray (5 gal./acre). development has sometimes proved eco- nomical and reasonably effective — with dense infestations. However, treatment under less than optimum conditions should be regarded as an emergency meas- ure rather than customary procedure. In some (as yet not understood) cir- cumstances, barban-treated cereal ap- peared to be slightly stimulated, resulting in higher yields in treated plots as com- pared with untreated plots, even where there was little or no weed competition. The prolongation of vegetative growth observed in cereals that have been de- layed in maturity after spraying with barban may either contribute to increased yields or be disadvantageous, depending upon other interacting factors in the en- vironment which affect growth and re- covery. The narrow spectrum of weeds con- trolled by barban may be a disadvantage where there is a mixed population of wild oats and broadleaved weed species. Wild oat control may be followed by an upsurge of broadleaved weeds, especially if there is some crop injury and reduced competi- tion. The action of barban is not spec- tacular in the beginning, and the final ef- fect is strongly influenced by growing con- ditions and crop competition. Sometimes, nonuniform emergence of wild oats may also pose a limitation to the effective use of barban, since many plants escape from a single spraying. These limitations, how- ever, have not prevented the apparently successful use of barban on a commercial scale in California. The limited tests with diallate were gen- erally less promising and less consistent than with barban. In certain tests (data not shown), diallate was completely in- effective when left unincorporated on the surface of the soil and unactivated by im- mediate rainfall or irrigation. Mixing the herbicide to greater depths than 2 or 3 [5] inches either reduced the degree of weed control (probably by dilution), or if her- bicidal levels were maintained, decreased the selectivity. This confirmed previous research. The phytotoxic effect of diallate on cereals, its narrow margin of selectivity and its erratic and unpredictable per- formance in several common agronomic situations posed serious questions as to its general usefulness under California conditions. Although diallate was not studied extensively for this report, the manner and depth of its incorporation into the soil, the amount and frequency of rain or irrigation, the depth and uni- formity of wild oat germination, the severity of infestation, timing of applica- tion in relation to seeding, soil type, and other factors, undoubtedly affected the results. However, these tests did confirm that diallate was almost as effective as barban for wild oat control when conditions were ideal. The timing of its application (pre- plant) could also be considered advanta- geous, since it lent itself well to normal cultural practices. THE PROBLEM Common wild oats (primarily Avena fatua L., but sometimes related species as well) are widely distributed throughout most of the cereal-growing regions of the world. Although sizeable acreages of volunteer wild oats are sometimes cut for hay, the weed causes serious losses — or sometimes complete crop failure — in most domestic grain production, both under natural rainfall and irrigated con- ditions. Infestations in California (the leading barley-producing state in the United States) are less severe than in the prairie regions of North America; how- ever, they constituted, until only recently, the single most important weed problem in cereal grain production in the state (Foy, 1961a). 3 Many previous studies have shown that the aberrant dormancy of wild oats, their great depth and irregularity of germina- tion, and their adaptation to a wide variety of soil and climatic conditions, have made the critical limits of herbicidal tolerance of both weed and crop difficult to estab- lish. Also, the similarity of wild oats to the crop that it infests often compounds the problem of control. While certain cultural practices have alleviated the problem, they have not re- sulted in selective control. Consequently, new chemical compounds are continually being tested by industry and by public service agencies. As many as two dozen compounds have been tested in California alone — with generally unrewarding re- sults. Barban, a new postemergent herbi- cide, and diallate, a new preemergent her- bicide, have, however, shown consider- able promise. But cereals have also shown varietal differences in their tolerance of or susceptibility to one or both of these her- bicides. THE EXPERIMENTS Three experiments were conducted in a field nursery of the Department of 3 See "Literature Cited" for citations re- ferred to in text by author and date. Agronomy, University of California, Davis, under weed-free conditions, to de- termine species and varietal tolerances of cereal grains to the herbicides; 62 experi- [6] merits designed to measure the effects of herbicide in terms of dosage, application methods, cereal tolerance, and yield were conducted throughout California on com- mercial fields that were naturally infested with wild oats. (Twenty or more wild oat plants per square yard is usually regarded as a heavy infestation; fewer than 10 plants is considered light.) The major part of the research was concerned with studies of barban. Both herbicides were formulated as emulsifiable concentrates, barban at 1 lb./ gal. active ingredient (a.i.), the diallate at 4 lb./acre a.i. No spray adjuvants were added to the formulations, which already contained solvent and emulsifier. CEREAL SPECIES AND VARIETY TOLERANCE TESTS Preliminary Test: 1958-1959 The first experimental sample of barban was tested on paired plots (treated versus control) with 22 varieties of barley, 15 varieties of wheat, 7 varieties of oats, and 2 varieties of rye — all of which were either in commercial use or being tested for per- formance in California. Although the plots were weed-free, barban was applied under conditions optimum for control of wild oats. Barban (1 lb./acre) was applied in water (30 gal. /acre) with a bicycle-mounted, boom- type sprayer when the cereal plants were in the two- to four-leaf stage. Crop response was evaluated visually for injury symptoms, percentage estimate of initial stand, and percentage estimate of tiller density of stubble. Grain weights from a 4 by 4-foot quadrat in each plot were also recorded to estimate probable yield response. Preliminary tests were not made with diallate. Results. Barban showed considerable selectivity among the four closely related cereal grain species (table 1). All plants of oat and rye varieties were killed, whereas none of the barley and wheat varieties were completely eradicated when treated with barban at 1 lb./acre. Although less conclusive, varietal dif- ferences within both the barley and wheat species were strongly indicated. Vigor ratings varied considerably among varie- ties; however, reliability of these estimates is somewhat offset by nonuniformity of the original stands. None of the barley or wheat varieties showed more than 45 per cent reduction in final stand, as estimated by stubble density (tillers, not individual plants) at harvest. For some treated barley and wheat varieties, yields were equal to or greater than those of corre- sponding controls; in others, yield reduc- tion ranged from slight to as much as 52 per cent. Thus, the possibility of both stimulation and inhibition of barley and wheat yield potential under appropriate conditions was indicated. Injury caused by barban varied widely between both species. Judging by all cri- teria, no generalization could be made as to which barley or wheat variety was most resistant. Barley and Wheat Variety Tests: 1960-1961 Both barban and diallate were investi- gated for crop tolerance with several common varieties of barley and wheat during two consecutive seasons. As in the preliminary test, somewhat higher than normal selective herbicidal rates were used in these more critical studies. The test for both seasons was conducted on a deep, fertile Yolo clay loam soil at the University of California Experiment Sta- tion at Davis. Additional experimental details are in table 2. Results. Results of these tests agreed generally with the preliminary observa- tions on barban (table 3). Some varieties in treated plots showed greater yields and some showed less than in the correspond- ing control plots. Similar results were ob- tained with diallate. [7] Table 1. Response of several varieties of barley, wheat, oat and rye to foliar applications of barban* in paired plots (treated vs. control) 1958-1959 Cereal varieties Vigor ratingf Appearance of stand Estimated standi Grain yield in treated plots as % of control Barley : 1 3 1 2 6 3 1 6 5 5 4 2 6 9 8 3 5 5 5 10 1 8 5 7 6 1 9 7 9 9 6 8 8 6 9 8 8 Very sparse Poor stand : late germ. Very sparse Very sparse Normal Normal Very sparse Sparse Normal Very sparse Very sparse Normal Normal Normal Normal Normal Normal Normal Normal Normal Very sparse Normal Normal Normal Slightly thinned Very sparse N ormal Slightly thinned Normal Normal Normal Normal Normal Slightly thinned Normal Normal Slightly thinned Normal Normal Normal Normal Normal Normal Normal Normal Normal per cent 75 55 65 70 90 75 55 70 90 95 75 80 90 100 90 90 95 80 90 100 90 100 90 85 90 75 95 75 95 95 90 90 80 85 100 95 100 per cent 48 Atlas M Awn Atlas H Awn 48 52 Vaughn Atlas 79 Atlas 57 84 Trail 85 White Calif. Mariout 86 Atlas 46 87 Naked Atlas 90 Hooded Atlas 92 Atlas 54 93 Hannchen 102 Calif. Coast 112 Calif. Mariout 112 Montcalm Arivat 117 126 Tenn. Winter 135 Rojo 148 Hiro 151 Kindred 174 Club Mariout 191 Wheat: 58 White Federation 70 74 Kiowa 77 77 Onas 41 79 83 Sentry 85 White Federation 54 Short White Federation 88 90 Bart 96 Big Club 43 114 Bart 46 117 Onas 53 118 Poso46 126 Oat: Indio Ventura Calif. Red Coast Black Nepal Rye: King * Barban emulsifiable concentrate was applied in water as a broadcast topical spray (1 lb./30 gal./A) with bicycle-mounted, boom-type sprayer when the cereal plants were in the 2- to 4-leaf stage. t Visual estimates based on a scale of to 10: = all plants dead; 10 = normal vigor (no herbicidal effect). X Visual estimate of stubble density, i.e., based on tillers, not parent plants, at harvest. [8] D O B 15 c o c D i_ D _Q O) C CN J) J3 Harvest method Quadrats: hand scythe Plots: combine harvester o o 4 X 20 ft., randomized block with 5 repli- cations (main plots, herbicides; subplots, varieties) 16 X 40 ft., randomized block with 4 repli- cations (main plots, herbicides; subplots varieties) 0) a > i a 02 "3 5 63 gal./A 112 gal./A a 30 gal./A 30 gal./A 0) a >> >> 2 a CO Plot: bicycle mounted Field : tractor- mounted, boom-type a 1 "a a cS "8 | 0) "3 s After seedbed preparation; just before planting After seedbed preparation; just before planting c 03 PQ 3-leaf stage 3- to 4-leaf stage CO .8 1 7 barley 7 wheat 4 barley 3 wheat E a H (1960) (1960-1961) ;_- & i jj a j - E X! > ..- fe a a o i — a a a -r $ cS - a o T) s o a ad >, 3 M 03 T3 ill O Vt-I »-H > o £ • in O o ° •S'S O) *H »H M O 3 > O o c >» c/3 S C 3 - 2 J2 ti ♦j c3 a> a** .9 e-S £ 23 G nd new d other cro mmendati c3 C o •- O 22 73 fe c -c £ O .-< 73 s^s< O a) rt ^ fr. .e U fc [9] Table 3. Grain yields, as per cent of untreated controls, from several varieties of barley and wheat treated with barban and diallate* Cereal variety Barley : Atlas 54 Rojo Arivat Calif. Mariout Tenn. Winter Hiro Wheat: Ramona 50 Bart 46 Poso48 Pacific Bluestem.. Onas46 White Federation. Big Club 43 Herbicide rates and crop yields Barban 1960 0.51b./A per cent 65 85 87 89 91 107 72 85 95 104 125 127 156 1 lb./A per cent 71 102 86 85 86 108 94 101 130 178 1961 0.5 lb./A per cent 93 97 107 111 89 Diallate 1.5 lb./A per cent 97 113 107 76 94 72 64 89 100 105 86 85 109 3 lb./A per cent 114 126 142 89 102 86 71 48 71 132 104 71 111 1961 1.5 lb./A per cent 104 99 105 104 102 105 111 * Barban was applied in water as a broadcast topical spray (30 gal./A) when the cereal plants had three to four eaves; diallate, as a preplant, soil-incorporated treatment. Refer to table 2 for experimental details. Relative grain yields varied not only among varieties each year, but also from one season to another for a given variety, although Atlas barley and Ramona wheat tended to group into a "more susceptible" category and Club Mariout barley and Onas wheat into a "more tolerant" cate- gory. Arivat barley was intermediate in yield response. Thus, the differential re- sponse of barley and wheat varieties to the two herbicides was confirmed. Com- pared with untreated controls, however, the relative yielding ability of any par- ticular variety was not entirely predicta- ble, due to the many changing conditions that influence growth and recovery from herbicidal treatment. WEED-CONTROL AND CROP-RESPONSE STUDIES These studies were made wherever suit- able grower cooperators could be found. They were designed to test the practical performance of barban and (to a more limited extent) diallate in fields naturally infested with wild oats. Land prepara- tion, fertilization, seeding, and irrigation (where practiced) were conventional for the areas in which the plots were located. All variables, such as herbicides, dosages, and the like, were kept as uniform as possible. Other variables, however, such as severity of wild oat infestation, soil type, spraying factors, method of soil in- corporation (with diallate), and environ- mental factors were not easily controlled. Sometimes, these proved confounding; at other times they were useful in the inter- pretation of overall results. [10] Application Methods Barban was applied with a hand knap- sack sprayer, a bicycle-mounted, boom- type plot sprayer, a tractor- or trailer- mounted field sprayer, or fixed-wing air- craft — whatever was most suitable in each situation. Spray volumes varied from 5 to 10 gal./acre by airplane, to as high as 103 gal./acre (in one instance) by ground rig. Rates ranged from Va to 4 lb./acre, postemergence, to wild oat-infested fields. Applications were made to coincide with the time at which most wild oat plants were in the Wi- to 2 1/4 -leaf stages. The only exceptions occurred when applica- tions were made at a later stage of growth of wild oats, for purposes of study. For barban, droplet pattern, spray coverage, and other factors influencing penetration were considered of key importance. Diallate was applied as a preplant, soil- incorporated treatment at rates of 1 to 3 lb./acre. The depth and manner of soil incorporation were varied among the ex- periments, and were most important fac- tors. Occasionally, because of the co- operative nature of some of the studies, some details were not available. Plot Size and Design Individual plot sizes ranged from 10 by 10 feet to more than 2 acres each, accord- ing to the site and method of application. The treatments were generally arranged in randomized complete blocks and repli- cated three to six (most commonly four) times. How Results Were Assessed Wild oat infestation was estimated be- tween peak development and harvest with a rating system (0 = none to 5 = heavy) similar to that used by the Canada De- partment of Agriculture (1959). In un- treated areas, ratings of 3 and above were sufficiently competitive to cause yield re- ductions. Actual weed counts were some- times recorded, in addition to the ratings. Weed control and crop injury were as- sessed periodically throughout the grow- ing season by visual observations, photo- graphs, and numerical ratings by two or more independent observers (see foot- notes to tables). Related data, such as plant counts, plant heights, and heading dates were also collected. Grain was harvested with a hand scythe, experimental plot combine, or field com- bine harvester, depending upon the size of the plots. Buffer strips were left for discard along the sides and ends of the plots to eliminate border effects. Grain moisture was about 12 per cent in each plot. Seed samples from several experi- ments were tested for herbicidal effects on germination and for herbicidal residue. Analysis and Interpretation of Results All grain yield data were subjected to sta- tistical analysis using standard methods as described by Little and Hills (1963). Most often, Duncan's (1955) multiple range test was used. Each experiment was analyzed separately, since site conditions could not be controlled. Critical com- parisons are thus permitted only among treatments within a given experiment. By comparing trends among the various ex- periments, however, general conclusions may be drawn with respect to the prac- tical performance of the two herbicides under a wide variety of California condi- tions. For ease of interpretation, certain procedural details appear in the results section. 1958-1959 season Three trials to study the effects of dif- ferent herbicide rates were conducted in three counties, on grain fields naturally infested with wild oats. Wild oats were sparser than usual because of weather conditions; however, satisfactory infesta- tions were obtained by careful selection of the test sites. The infestations were rated "light," "light to moderate," and "moderately heavy." The varieties treated proved to be either among the most sus- ceptible or intermediate in susceptibility to barban. In these early studies, barban was ap- plied at rates ranging from low to ex- cessive, with a relatively high spray vol- ume. The herbicide was applied by hand sprayer under optimum conditions for wild oat control and crop safety. Yield responses and other data in the three ex- periments are shown in table 4. [in Table 4. Effect of barban on yields of cereal grains infested with wild oats (1958-1959)* Yield Rate of barban Arivat barley (Yolo County, t light infestation) Ramona 50 wheat (Tulare County, light to moderate infestation) Atlas 46 barley (Colusa County, moderately heavy infestation) Ib./A cwt./A 19.1 19.5 13.7 7.9 11.3 cwt./A 18.4 20.2 12.8 3.1 2.0 cwt./A 20.2 y 2 26.5 1 21.7 2 12.6 4 10.5 L.S.D. 5% 3.8 5.2 5.0 6.8 3.5 1% 4.7 * Each value in this table is the average of six replications. t Grain lodged considerably. Individual plants in the sparse stands resulting from injury at the 4 lb./A rate were not so severely affected. Fig. 4. Wild-oat control plots in Atlas 46 barley, Colusa County, 1959. (A, left) sprayed early post- emergence with barban, 1/2 lb./ acre, and (B, below) untreated con- trol showing moderately heavy wild oat infestation. Yield increase due to treatment was 6.3 cwt./acre. .'.:,:.. ' : kl The results agreed well with preliminary findings in the field and greenhouse. True selectivity for wild oats was obtained with very low rates of barban in both barley and wheat plots. Initial injury to the cereal was in direct proportion to the rate of barban applied. Rates in excess of Vi lb./ acre caused crop injury that resulted in reduced yields at two locations. Yields from the Vi lb. /acre plots equalled or surpassed those of the untreated plots, de- pending on the degree of the infestation. In one case (moderately heavy infesta- tion), barley treated with 1 lb. /acre yielded as much as untreated control plots. Although barban at the Vi lb./acre rate did not materially reduce stands of wild oats in these early experiments, the plants were obviously weakened. The slow herbicidal effect was later aug- mented by crop competition. At harvest, wild oat plants had produced some seed heads, but they were 6 to 20 inches shorter than those of the crop or of wild oats in adjacent, untreated areas. At one location, barley was relatively free of wild oats at the height of cut with the combine harvester. 1959-1960 season By now, both barban and diallate ap- peared to be promising herbicides for wild oats, and evaluation for their possible use under actual field production conditions was clearly indicated. Barban was tested in 17 locations on barley and wheat at 0, Va , Vi , and 1 lb./ acre (table 5). The chemical was applied by hand-operated or tractor-drawn field sprayer at a volume of 7 to 55 gal./acre. The early postemergence applications were timed to coincide with the period when the largest percentage of wild oats was in the IV2- to 2 l A -leaf stages. Barban at 1 lb./acre caused noticeable injury to barley and wheat, but did not reduce stands or yields in fields heavily enough infested with wild oats to justify herbicidal control measures. As reported by Holmes and Pfeiffer (1962), as well as others, the capacity of the crop to recover after treatment with barban was quite high. In no instance, regardless of the severity of infestation of wild oats, did barban at V* or Vi lb./acre cause a re- duction in grain yields. Yield increases, on the other hand, were directly de- pendent upon the degree of wild oat in- festation. With infestations rated as "wild oat-free," "very slight," and "slight," the yields were not significantly influenced by treatment with barban. Fields rated as having "moderate," "heavy," or "very heavy" infestations, however, showed in- creased yields or trends toward increased yields. Both crop and wild oat plants were sometimes stunted initially at the 1 lb./ acre rate of barban. However, the crops recovered, while the wild oats were slowly suppressed or killed. Again, final weed control appeared to be strongly enhanced by crop competition. Diallate was studied in limited tests at 1 1 locations — sometimes in the same fields with barban experiments (table 6). The herbicide was applied to the soil, be- fore planting, at rates of 0, 1, 2, and 3 lb./acre, by disc, harrow, or other tillage equipment available. In general, the control of wild oats was fair at the 1 lb./acre rate, and good at higher rates. Crop injury occurred in several instances. The degree of injury, as indicated by visual symptoms and by grain yields, ranged from slight to severe as dosage rates were increased. Even at the lowest rate tested (1 lb./acre), yields were lower or tended to be lower than in untreated control plots in about half of the experiments. For the limited number of varieties used, wheat generally ap- peared to be more severely injured than barley. Soil incorporation of diallate, usually 2 to 3 inches deep, was essential for suc- cess. Although most uniform incorpora- tion of herbicide is provided with a power-driven rotary tiller device equipped with L-shaped tines (unpublished data), such equipment was not readily available for these studies. Ordinary farm equip- ment (disc, spike-tooth harrow, spring- tooth harrow, cultivators), such as that employed here, gives notably uneven ver- tical and lateral distribution of herbicides in the soil (Holroyd, 1964). This may account, in part at least, for the erratic results with diallate in this experiment. 13 "5 *E o ° a IS £ -u ? u ^ t a a> .2 ° U CL O _2 J2. ^ o E <" D i_ »_ w o ^ s ~^ -D O o D > CD C D _Q i_ O _Q u c D E — o i- a> a. 03 s PS Rainfall 5.6 inches. 5 inches sprinkler irrigation last half of March. Wild oats in treated area 1-2 ft.; un- treated area V/z,-\ ft. Wild oats were present in all treated areas but they were much shorter and con- tained only 3-6 seeds per panicle. Combine harvested more wild oats in seed from un- treated plots. 6 inches rainfall. 5 ■3 03 ,3 O .S c' . O 3 Is » 2 « .5 Is 03 "S bB 03 2 g H 4 inches rainfall. Adequate moisture most of season- better competition than Kings Co. test (1). Treated wild oats 12 inches tall. C _o 3 1 S-. 03 M g O 'a 3 3 O 3 O 02 . ti 33 3 03 -g « "s 43 ° -3 O 3 03 3 co T3 7 inches rainfall. Wild oat plants not killed immedi- ately. Slowly suppressed. Removed from competi- tion. No seed set. 7 inches rainfall. Wild oat plants not killed immedi ately. Slowly suppressed, removed from competi- tion. No seed set. n 1 1 . co' cwt./A 43.2 n.s. 47.1 52.5 51.3 26.2a 28.5 ab 30.8 b 27.7a 15.1a 15.5a 21.2 ab 23.5 b CO (H i-^ -t-> ^2 03 o3 O -Q 01 ra n Tji x, 03 rO O 03 O 1-1 O0 CO CO a CM CO Ol CM »o 00 02 «s n * s CM CO CO CM O CO t^ 00 CM CM CM CM a^ S3 o o o o O © — 1 CM 0000 OOOO + O ^ h N 1 O O r-l ^H 1 O © O I-" 1 o 3 o O O CO ■* Tf< O Od CO CO O CM CO ^ O CO -*f -^ O CO ■* Tt< O * IO ■* O ■>*< >0 iO co 3 03 o CO CO * CO > "3 CO 03 03 Js a Eh £ >> 6J Surprise fine, sandy loam a 03 O co 03 03 O Q Lockwood sandy loam PI i C a.2 Co *»« 03 +3 a£ DQ0 Knapsack, 8003 Teejet, flat-fan, 55 gal./A Knapsack, hollow-cone, 27 gal./A Knapsack, flat-fan nozzles, 27 gal./A Knapsack, flat-fan nozzles, 27 gal./A a<5l Hand-sprayer, 8004 Teejet nozzles, 27 gal./A Hand sprayer, 8004 Teejet nozzles, 27 gal./A STJ c3 Oj ^ >«**- ° ^^~ °^^^ °^^~ °^^^ °^^^ °^^^ .S o3 > a 03 2 6 3 _0 'u 03 03 ^ Is ^ 5 3 *1 03 »g 72 03 o3 ^ pq 5 3 >> CD ■£ "S 03 pa S 03 03 3 o3 'S PQ S 3 .2 03 03 r3 "3 "* Barley (Atlas 54) ■v a a > c s c a 03 a "o3 1 O o co o 6 3 » 8 B oo CM 3 03 CO 03 c B 00 CO 03 B B a -0 <; 03' ^ 03 ^2 -^ 43 £ 3 Id [14] 3 03 'B a •3 a a J3 "S d .5? 2? 2? 5 ° £ 3 >>2 ass O .H H -° ^ ,_ v ."g ft 3 d £ 6 3^ 3 8 i 53 1.1 =3 O " >rt O O O ^ + I O ■* "O U5 O 03 O « .a s 3 O o ® o £ ~d 3. = s 2 Q s I T3 » fit 5 +2 > -a o bfi 03 3^ DO "18 -a c3 -c 8 .2 - s « 5 2 •sis >> -^ co Sox a ° 15 (M CO — < CO 3 •£ ^ as t; a « 8 $ P. £ 2 o PQ s ^ -* 43 03 O r-S~ .a s a CJ 43 w £ d^ «c -a ^ a "to 03 o o J 9 |-2 C3 43 w TJ SI'S « H c s^ >> C3 M H c » 3 53 CJ 03 x: -' "3 O "15 N 6 « § T3 o >> c3 £b .2 ~ 02 ^ O IS 15] a t3 O t3 5 % 3 a o > OJ £ Si o » V a S3 ti £2 o 1'1 o ^ "cS 11 BJ* o!s "S a cs '3 is 8 c * T3 A -a " T3 « 2 a 2 t^ O '2" w .5 £ s CO 03 co too c oj s> s> xt 3* 2 OS "tf CO lO ^ t-, o rt rt CO Oi r-l "oS N ffi O) > £S -i O-ff 1—1 ■ rt o 1h ^ + + + * O 00 1 •**" OMTf* O l a eS fS o O — o> 3 a o 8 o O § o a fl Ql s s i o a.2 3 cS S-, u crS *> H> e <0 *>:3 m >> g >> >, Mft5 2 -3 ft, N & § c3 ™ c3 a CQ o3 ^JS- °^^~ °^^^ >> .• 'C c8 > o T3 c3 O c 03 +j o >> "S >i "S a o O s 1 11 $ Bj+3 -o e ■si *i J^ "» G <° ?? >>£ CNI T-l S3 ^ 2 " a* 3 <0 ,Q •3 t- 3 a3 3 c. c S c > , ^ S «la« a^ 03 a § ^ O « -7-t 3 .5 o s a. a> § •- 1 8 osfl d O c|-3^3 05 T3 e3 '55 -^ ■? (3 J, 41 -g i •2g^ •gss .- Oco Co I Out. be a> o JLls O - [16] In other tests (data not shown), diallate was completely ineffective when it was not incorporated in the soil and not fol- lowed immediately by rain or irrigation. This was probably due to loss of the her- bicide by volatilization and failure to be activated by rainfall or irrigation soon after application. Diallate has been shown to be active, herbicidally, in the vapor phase (Friesen and Henne, 1962). Mix- ing the herbicide to greater depths than 2 or 3 inches either reduced the degree of weed control (probably by dilution), or if herbicidal levels were maintained, decreased the selectivity. Friesen et al. (1962), Parker (1963), Holroyd (1964), and others, have found the depth of place- ment of diallate to be important with re- gard to both initial toxicity and selectivity toward the cereal. Parker and Holroyd also indicated that optimum placement is apparently variable depending on the species and/or variety, the temperature, and when the herbicide is applied in rela- tion to seeding. Results in this experiment agreed with those of Faivre-Dupaigre (1963), who obtained good control of wild oats without damaging the cereal (except under cer- tain soil conditions), at 1 lb./acre. Gen- erally, however, serious reductions oc- curred in yields of barley at 2 lb./acre. (Compare table 6 with table 9.) Similarly, Evans (1962) obtained good control of wild oats under favorable conditions with Vz to 3 lb./acre; however, obvious toxic- ity occurred to the crop at 3 lb./acre, and sometimes at \Vi lb./acre. Poor wild oat control in those studies was ascribed to "poor soil conditions at the time of the incorporation of the herbicide into the soil." 1960-1961 season Further studies with barban and diallate were conducted on fields where wild oat competition was thought to be serious enough to justify the use of herbicides. Results and experimental details are pre- sented in tables 7 and 9. Barban. All applications of barban, from l A to Vz lb./acre ( 1 lb./acre in one instance), with ground sprayer or by air- plane, and with spray volumes ranging from 10 to 103 gal./acre, resulted in in- creased yields or trends toward increased yields as compared with untreated con- trols (table 7). Wild oat control ranged from poor in a few cases to excellent in most cases. Poor or marginal results were always associated with improper timing (when wild oats were beyond the 2Vi- leaf stage), drought stress, or other ad- verse growing conditions. In most instances, an attempt was made to relate the effectiveness of barban to various conditions at the time of spray- ing. In the four Monterey County experi- ments, for example, advanced maturity of the wild oats, drought stress and, pos- sibly, frost tended to reduce the weed control achieved with Vi lb./acre of barban (table 8). The 1960-1961 trials (Fresno County), as well as the 1959-1960 trials (table 5), indicated that when higher spray volumes (55 to 103 gal./acre) were used, more actual herbicide per acre was required to accomplish complete weed control. Uniform spray patterns were more easily obtained with ground rig than with aircraft. However, results from the 1960- 1961 studies in Glenn, Sacramento, and Yolo counties as well as other studies (data not shown) demonstrated that air- craft often can be used effectively, if care is taken to spray evenly. Uneven spraying (missed areas) by aircraft, or spraying with inadequate dosages of barban, can cause streaking in areas where wild oat growth is uncontrolled. Uneven patterns can also result from crop injury or de- layed maturity in strips receiving higher than normal dosages of herbicide. De- layed maturity of cereal grains, not an uncommon response to higher herbicidal dosages of barban, is usually considered undesirable. Sometimes, however, delayed maturity may be advantageous. In the 1960-1961 Glenn County test, for example, more stooling, probably larger grains, and cer- tainly fewer blank heads occurred in plots treated by air spray with 0.4 lb./acre barban than in the untreated controls. These factors might have reduced the vulnerability of the barley to spring frost. Studies in England, on the competition between barley and oats (Pfeiffer and Holmes, 1961), showed highest increases [17] "5 'E -7? o * -2 O n 2 £-§ * u to ^o £ £ 11^ O «/> *+- u >> m £ ° « _o> jo E o o E "> O D . si to O 0> w -o 0) Q. ul T3 03 d o ^ d 03 3 03 X! 03 CO »o ej 03 d « C d -o .2 43 o 3 US d 1 03 3 § .2 3 M 03 ^j. d 03 "2 a "8 "3 _o a '3 o a| 03 _s o '8 a s 03 £ *o 8 d |-S 03 4* (-, S3 03 03 03 43 43 -g o d £ 43 o d d co +r; o d Be d ^ g 43 d ° d ^ o * ■-J3 ° ti "! o o T3 o ,—3 CN 03 ol 43 :=3 d 03 •{* "8 a •S 03 3 '3 -5 d ^ "3 ^3 o3 "d 4s a •| .a > «£ a «£ 2 2 8 43 o .s >-i "b 03 o o 02 03 J 43 o s . ■11 4) d S § 43 O t3 -f 8 j§ d -a 3 2 2 d S II a o d 03 ,rt d "0 S "5 3 Oi lO O rt< T3 03 ^ «, 03 03 03 „a o «/= ^ CO 42 4^ 42 d d d C8 03 42 O 2 ,J O O CO CO CD t^ CM OS 00 « <* « N ffl ffl * t^ CO "■*< O H 0O ifl N S Ol o * co O if i* 1 ■* O CO Tf itl "3 O 2 o O a ^ d"^ * CO co CO -* co g| a a d >> _d '3 >> * \ is c 03 03 "2 o J 03 _i 43 « 03 o 03 d 43 03 s a O >> &S | a c o 03 cd ,2 o d d c 3 £ , < u CO ^ *0 "3 •oS n 03 O a .a 13 ft J5 .S 1 .S 00 T3.S 3 -? 8 -d -d -^ o o d O —i "V °° 03 nd U 03 03 03 -^ -d ^3 «*3 -? ^ 03 43 O 03 o.S S g -S «> % ■% C ^3 .h h a • •- 03 bD 44 ^ d .2 8 l 0) u 03 s .2 & Q ^ 1 1 Ph 'ft ^ 03 a ■a | $ •w 03 q, -d 03 43 w *T3 J5 .* la a O i-h (M CO O H pa. o- J3 d is ^ tj- § a 43 fl 13 3_ '8 °° 03 • 03 d C J O w O £ o § § [13] cp "5 s 5> CO J& 5 JO o CO O . 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CJ >> ^ O 03 J5 " p CO TJ 3 2 3 CJ OJ 'S, -^ CO 3 co o CT: CM 03 X) O HON ■C lO "J -h (M CO 03 -Q o o d —^ co ■* a"£ CM O 1 o o o o o o o o o o o 08 Sh -SI £8 O iO O CO O «tf> CO O 1 CM O "5 CO O "5 O 1 o co «o O «3 ^ CO o CM o CM O © £a "3 t- 3 » o g 6 % CO a o3 "ft 73 Jh o g -3 t* o g -3 ^ O 03 T3 i_ 3 cj c g o a 73 t- CJ 3 a T3 «-, o g CO a3 OJ Is* °o °^ °^! °^! ° ^S\ °^ °^ °^ °^^! ° ^ a'fi O o3 c3 Hi "3 >> ,2 3 PQ >> o3 3 _o 03 cj |s Hi "3 |1 3 _o 03 a S? Jj SB CJ 03 PQ 03 PQ 03 PQ 1 "5 2 >> c 3 o O o s co 0/ s a s CO M 3 s a? CJ C o >> CJ CJ "3 o >> OJ CJ 3 o CJ CJ ft o 03 V 1 a o OJ a 5 si m CJ o T3 O 3 O _>> o o T3 O % 3 O .b IS co 33 [20] o o s c3 3 3" n (_ 4) a CO 3 a 1 ? CN CO o o CD c3 OP CO <5 a CO O CN CO ei ,3 t M CN1 oi oo fli <-i CN CM o -* © CN CO •<*< O "3 o "» »o »o o oo 3 a t-, -3 t- 3 ? O g O a ° ^ ° ^^^ 3 As 3 O 1 Hi "* c CN o -^ « £ K O 3 3- w » & 3 £ ** 5 3 "3. -3 eo _- 03 £>■£ c'S 3-3 8 O • - g a> on of ^b oJTJ-^ C 1511 • ill Js-2 8> 5 2 2-3 8.J -o J, ««* fc.~^.90 V a. ! 3 C J. .3 £ 5 5 ; * 3 03g-3 H ■ • S I .§ O S 3 3.5 O O.r-, o.^^ |-agg in barley fresh weight with the lowest seed rate of barley, despite the fact that these plots still were partially infested with wild oats at harvest. Other changing environmental conditions may also be ex- pected to alter the normal growth patterns of cereals, and thereby influence their final response to herbicides. At one location (Yolo County), bar- ban, both ground- and air-sprayed, caused far greater injury to barley than had been observed before in these tests. When rates were reduced to l A lb. /acre and below, however, the crop made a remarkable re- covery, and yields were equal to or greater than those in untreated plots. The high degree of injury in aircraft- sprayed plots (V2 lb. /acre) was similar to that obtained with ground spraying at ! /3 lb./acre. This may have been caused by inclement weather which delayed the spraying; also the solution stayed in the aircraft spray tank for two weeks before application. The uneven spray distribution resulted in some dark green streaking and Fig. 5. Wild-oat control in barley, Glenn County, 1961, fol- lowing aircraft application of barban (0.4 lb./acre) in 10 gal. /acre spray volume. Note untreated area in back, treated area in foreground. Barley yield was increased 8.2 cwt/acre due to herbicide treatment. • ■•■!•*£ ;■ ■■'■'-. Fig. 6. Wild oat control plots in California Marious barley, Yolo County, 1960-1961. Note unprec- edented early crop injury (left and right of untreated center strip) due to ground spraying with barban (Vh Ib./acre) under adverse environmental conditions. The barley recovered, however, and the grain yield was significantly greater in treated than in untreated portions of the field. delayed maturity. Other factors which may have contributed to this unprecedented high degree of injury with barban were the slow morphological development of the crop plants at the time of treatment, prolonged periods of wet, foggy weather preceding treatment, and frost, which oc- curred intermittently both before and after spraying. Holmes and Pfeiffer (1962), however, found no obvious cor- relation between increased crop sensitiv- ity and either temperature or develop- mental stage. The factors accounting for the increased herbicidal activity in such exceptional cases as this obviously require further investigation. Dial late. Of the seven tests using dial- late, two showed significantly increased yields due to treatment, despite some early injury to the cereal (table 9). In all other tests, except one in which no yields were taken, the tendency was toward reduced yields, although the differences were not statistically significant. Based on the er- ratic weed control performance and nar- row margin of selectivity in cereals ob- served with diallate during two seasons, extensive field testing of this herbicide was Table 8. Relative effectiveness of barban (V2 Ib./A.) against wild oats under four different California conditions (1960-1961)* Location Growth stage of wild oats Vigor of wild oats Field conditions Wild oat control Long Valley San Lucas. . San Ardo. . . Bradley VA to 2V 2 leaf W 2 to 4 leaf Wi to 2Y 2 leaf W 2 to 4 leaf Drought-stressed Drought-stressed Excellent Frosted Drought-stressed Drought-stressed Excellent Fair-good •per cent 80 30 95 70 Locations correspond to Monterey County experiments 1 through 4, table 5. [22] u D CD 42 a o * ° ^o .E £ IS* u >. _a> "> E & "5 E i_ i_ «« £ 8 w a) D _D D > 0) o Jo "o u c a E ■g a. Os -Q 00 s a ®, Wild oats germinating from November rains were con- trolled. Those germinating from January rains, poorly controlled. Barley planted 1 week after treatment. 73 OJ W -d OJ j>> a> S > © T3 3 J CO a p O 2 \ O oo | O M u co 3 OS OS OS O CM o CO O > "3 .22 OB X O a ,3 a ■* .a p .s a g a _ IP* p . a a i 1| 73 O o p. II Is C > a "a CO o o he * a ,g a 3 CO o $ s 3 > 5. 3 CO o a 0) Ov -a ai oj ,4 - o * s 2^ w 5 CO . bo 3 5 -s -8 1 1 3 -^ ^ ^ t- o o o •« b Q o c a _g co a c a j &^-« t 3 ~ "§ i -H o o a - ■£ 3 « a 2 5-0 a .g la o^ oJ o\ N o^ O -^. CO o^ >> .® c3 > c 03 a o 6 >> 03 pq >> _0J 03 PQ $3 IS 3 3 pq^ >> ,2 03 PQ 5 03 pq «1 >> s O O oi S < o a CO >> a> 0) 3 o 9 o c o 03 0) CO § a 3 o o T3 o 3 O .b CO CO c5~ o o "3 1 3 O >» co CO 1-a ^> 00 OJ i*l A aj C 3 t>o aj 'C 3 a 5 03 X X OJ a) cat O jh 3-- 0--S- 80 3 O ^ fl OJ ^ 3 if ® Si -a «>_- .. , OJ OJ w 2^ >* 3 -^ oj-3 £b-.§ • - . > OJ CO iC" oj" ■■3 * >>-J3 03-373 3 .2T5 c ® 73;- o3 -^ ^3 '53^ S 1 2 ® oj 3 « <*. 03T3 o3 Tll-ll co > V o3 3 -^1 ® !! c3-° w .5.2 o -a -^ 03 co fS*3S. 0^x8 O CO - wj I s b'r^ 2 ^ oj o a^i 3 O £ "1/S 3 «.s 1 Js ifcl 23S5S +3 OJ 03 & 1.2 [23], 42 D 8 Is ai-g Us o> .32 ° t3 a. o _2> *" E w a> d © D _D o > a 33 CD ■* 03 11 3 aJ fJJ-p o3 bfi o — o 3 "flfl) 2 ™ ^ a ^ ° tx © Tl -£" <*> 2 3 H2 3 •g 03 P CD CI H T3 Tt< 9 .a •-'£ ^ °3 ^ 03 £ 3 T3 bo -£ « § * 8 S > * 03 O 03 t° 03 ^ gs § 03 ^ 'g'a 03 ^\<*H ^ rC| bo d> 03 c-5S § « a 5 St; ^3 03 -C bfi oj ^1 «* a ft -2 g ft CM ^ as d 03 o >0 r«i -§5 S5 a '5 & |«i _, « s J3 m © ■Be? Ph & o3 12? ,£3 S3 ^3 a3 X! 03 tn 03 ++ •^ 03 ^O J2 c o3 X> 03 -ft 03 rQ a 03 J2 ^3 X3 -Q -Q fi 2 "33 ~>CO »-i »o ■<*■ i« © iO • CM © CO Oi OO CO 00 00 1H IC CO 00 lO (M «5 m lO H !C NN a. ^ SNOCD cm" co co r^ • CO CM ■"*< CM oi «o r-i Tt< i— 1 CO CO 00 UJ N OO S OO N lO if !D 1(3 «5 £ 2 CO rt< CO co co co co i-i CO CM CO rt CM ft"£ 2S Ornffq o o o o o o o o o o o o o o o o © O O O i-H ^ (M O O O ^ i-H o-g- "* gfe O ^ ^ o •* ■>* ^ O CN CO CO CO o «o o »c o «o o »o Oncco iflm OMCJifliO *s* SI ^T • ° ° • © a> © • iO O "5 O • t^ • «5 •*i l^ •* t^ Ir^ • tooidod ■* N ■* N • CO O CO O 52 ' *" H *"" ' CM CM CM CM CN CM CM o> o m H02 at C! T3 tn T3 M -O i* *„ T3 t, CI T3 tn ^ fet efl C « C « C J C ¥ c ¥ 03 C © c ^ ft <3 o 2 n ft O 02 §2 o g 3 o? o a 3 2? 3, 3 3 b o g 2 S CT3 o3 43 ^ M ft PQ 03 °^^ °^^ °^ °^ O \o °^ °^^:^^^ ®^^^^ >> .2 'S 03 > 3 T3 CI 03 >> >> >> 9 ? ? >> >> >j a a> ,2 J& CD g cS £ 03 2 ^ rS j> o *£ t, o3 k O 03 PQ 03 PQ pq fSB c3 PQ 03 pq 03 PQ ^^ ^^ (M CO 8 o o O £ -d t; o o o a 3 ^^ >> d o § § % O O o c s CM o CI h O >> .2 DQ h o >» 2 3 o >. 'si in o S o CO J0 o "3 [24] discontinued, and attention was focused on barban. 1961-1962 season Studies (with control plots) were made to refine specifications for the consistently successful use of barban under field con- ditions (table 10). Additional rates of her- bicide, various spray volumes, and later- than-optimum timings of application were introduced as variables. Both air- and ground-spray applications were made. Wild oat control, crop response, and yield data are shown in the table. Barban provided excellent control of wild oats in both barley and durum wheat, and substantial yield increases were real- ized in all tests when the herbicide was applied at the optimum stage of growth for both wild oats and cereals. All plots carefully and uniformly treated at the optimum stage of growth, with barban at l A, V3, or Vi lb./acre, and with spray volumes ranging from 5 to 40 gal. /acre, yielded more than untreated controls, and were about equally effective. Wild oat control and the resulting yield increases were diminished when ground- spray applications were made later than optimum time on more advanced wild oats in Yolo and Monterey counties. In Mon- terey County, for example, where barban was applied when 60 per cent of the wild oats were in the 2 1 /2- to 3-leaf stage, 20 per cent in the 3- to 4-leaf stage, and 10 per cent in less than the 2Vi-leaf stage, control was extremely variable. Although application was made at later than opti- mum time for wild oat growth, many plants were deformed and did not set seed normally. As reported earlier, these plants were not actually killed, but they stopped growing long enough to allow the crop to overtop them. Although no yield increases were realized in such instances, treatment might still be regarded as bene- ficial. Differences due to spray volume were not striking during the season, and differ- ences due to rate of herbicide were less marked when barban was applied at 20.7 and 6.4 gal. /acre than in earlier tests when higher spray volumes were used. In one low-yielding experiment, spray volumes of 20.7 gal./acre appeared to give better herbicidal effect and greater yield in- creases than did 6.4 gal./acre, when the applications were properly timed; how- ever, actual differences were insignificant. Although frost injury and drought con- ditions may directly affect the overall de- gree of wild oat control and cereal toler- ance, associated factors also must be considered. In Yolo County, barban- treated areas were clearly distinguished by the decrease in vegetative covering and the yellow-green color of remaining vegeta- tion. In addition to the usual suppression of wild oats, barley seemed to have been injured slightly by barban or made more susceptible to frost injury — either as a di- rect result of treatment or by reduction of wild oat competition, which allowed greater exposure of barley to freezing winds. In time, the barley recovered, while the wild oats remained suppressed. Even six weeks after treatment, however, barley appeared to be more frost-injured in treated areas, which may have been due in part to the lack of protection against the cold wind afforded by wild oats in untreated portions of the field. Whether frost was a factor or not, the V2, lb./acre rate of barban showed better wild oat control and more barley injury than did the l A lb./acre rate. Barley injury ap- peared worse in areas of low fertility, poor drainage, and low water-holding ca- pacity. Although the injury appeared to be due mainly to frost, causal factors could not be determined with certainty. 1962-1963 season Many test demonstrations with barban were conducted following its recommen- dation for control of wild oats in barley and wheat. When the same parameters or variables were used as in previous tests, the results generally confirmed the con- clusions reached earlier in this report; therefore, detailed experimental data are not presented. However, two other (somewhat excep- tional) experiments were made in Fresno County to study the effect of barban on the yield of barley grain where wild oat plants ranged from the one-leaf to well- tillered stages of growth (i.e., later than optimum) at the time of spraying. The [25] Fig. 7. Typical, progressive development of injury symptoms in wild oat plants sprayed with barban at recommended rates. Treated plants are at right, untreated at left, in all photographs. (A, upper left) first day after treatment, no visible effect; (B, upper right) after five to ten days, growth ceases and treated wild oat plants appear stunted in comparison with untreated controls; (C, lower left) after approximately two weeks, wild oats noticeably stunted, bluish-green in color and beginning to turn brown; (D, lower right) after four to five weeks, most sprayed wild oat plants have died and turned brown or remain severely stunted. Competition with the cereal grain would be essentially removed. herbicide was applied at two rates, Va lb./acre and V3 lb./acre, by fixed-wing aircraft using 10 gal./acre spray volume. (Each value in the text table was the aver- age of three replications.) While previous tests indicated that earlier applications of barban produced more consistently ef- fective results, these tests also showed that treatment was profitable. Both dos- ages increased yields equally, despite only moderate effectiveness against dense stands of wild oats that varied widely in stage of development. (All yields were somewhat lower than normal, perhaps due to moisture stress early in the season.) Experiment barban APPLIED Yield : IbJA cwt./A 1 15.1 Va 19.6 Vz 2 Va 16.8 1/3 21.3 * Yield values of treated and untreated plots in each experiment differed signifi- cantly at the 1 per cent level. [26 SEED VIABILITY AND RESIDUE STUDIES Seed collected from several experi- bility, however, as measured by final ger- ments (1958 to 1961) were germinated mination was not affected by spraying the in the laboratory, between moist filter crop with barban at rates of 1 lb/acr e or paper, in Petri dishes, at room tempera- less. This result is consistent with the de- ture In seed from barley that had shown tection of "no residue ' in grain samples barban-induced delay in maturity in the submitted to the chemical company or field, germination was rarely retarded, analysis and with results with C labeled and then by only a few hours. Seed via- barban in our laboratory (Foy 19616). ACKNOWLEDGMENTS The authors gratefully acknowledge the assistance of the following cooperating agencies and individuals: Specialists of the Extension Service and University nrf ! Cali- fornia Farm Advisors; staff and technical assistants of the Departments of Agronomy Agricultural Engineering, and Botany, Davis; and various California growers. Although the individuals who participated in the program are too numerous to mention by name, the valuable help of each is nonetheless greatly appreciated. The barban used in this study, as well as partial financial support was provided by the Spencer Chemical Company (Gulf), Kansas City, Missouri; diallate was supplied by the Monsanto Chemical Company, St. Louis, Missouri. Photographs on the cover and pages 4, 5, and 26 were supplied by the Gulf Oil Corporation. GENERAL REFERENCES E 1 L 962 S ' Barban for controlling wild oats in cereals. (Abstr.) Tijdschr. PIZiekt. 68(3) :210. Also in Weed Abstr. 12( 13) :627. 1963.) Appleby, A. P. 1960. Selective wild oat control. Proc. Oregon Weed Conf. 9:37-38. Atwood, W. M. A. " _ -- 1914. A physiological study of the germination of Avena fatua. Botan. Oaz. a/. 386-414. Edwards, C.J. „.... .. 7 , 1961. Progress report on barban. Agric. Merchant 41(10) : 70- /z. Faivre-Dupaigre, R., J. Rognon, and M. Ballacy 1 963. Destruction of wild oats {Avena fatua L.) in crops of spring barley. 2 Com. Com. franc, mauv. Herbes (Comma). (Also in Weed Abstr. 13(1):1«. 1964.) FlDDIAN, W. E. H. u^u,v;,w 1 962 Relative susceptibility of cereal varieties to some commonly used herbicides. Proc. 6th Brit. Weed Control Conf., pp. 203-214. (Also in Weed Abstr. 12(2) :331. 1963.) [27] Foy, C. L. 1961. Wild oat herbicides — a report of progress. Proc. Calif. Weed Conf. 13:99- 108. Foy, C. L., and D. E. Bayer 1961. Field evaluation of 2,3-dichloroallyl-diisopropylthiolcarbamate (Avadex) and 4-chloro-2-butynyl N-(3-chlorophenyl) carbamate (barban or Carbyne) as wild oat herbicides. Res. Prog. Report, West. Weed Control Conf., p. 48. Friesen, G. (Summarizer) 1961. Cereal crops and corn (12 reports. Res. Rep. W. Sect. Nat. Weed Committee, Canada, pp. 124-32. (Also in Weed Abstr. 12(4) :891. 1963.) Friesen, H. A. 1961. Some factors affecting the control of wild oats with barban. Weeds 9:185- 94. Friesen, G., and R. C. Henne 1962. The effect of 'Avadex' vapours on wild oat seeds. Proc. 9th Ann. Meeting Agr. Pest Tech. Soc, Ottawa, pp. 5-10. Haun, C. R. 1956. Dormancy and germination studies of the wild oat (Avena fatua). M.S. Thesis. Montana State College, Bozeman, Montana. Hoffman, O. L., T. R. Hopkins, and J. W. Pullen 1958. Wild oats — a new chemical control. Proc. Nat. Weed Committee (Western Canada Section), pp. 3-6. Hoffman, O. L., J. W. Pullen, J. R. Epperly, and T. R. Hopkins 1960. Factors affecting the activity of 4-chloro-2-butynyl N-(3-chlorophenyl) car- bamate as selective herbicide. Weeds 8: 198-203. Holly, K. 1960. Pot experiments with new herbicides for the control of wild oats. Proc. 5th Brit. Weed Control Conf., pp. 533-41. Leighty, D. H. 1958. Dormancy and germination studies of the wild oat {Avena fatua) M.S. Thesis. Montana State College, Bozeman, Montana. Lute, A. M. 1930. Germination characteristics of wild oats. Assoc, of Seed Anal. No. Amer. Proc. 33:70-73. Rademacher, B., and M. Amann 1963. Control of wild oats in German varieties of spring barley. Mitt dtsch. LandwGes. 78(12) : 396-98. (Also in Weed Abstr. 13(1) :20. 1964.) RlJKSLANDBOUWHOGESCHOOL, G. 1960. Winter and spring cereals. Specific and varietal differences in susceptibility of cereals (to herbicides). Beknopt Versl. Centr. Onkruidonderz. Gent., pp. 13-16. (Also in Weed Abstr. 12(2) :338. 1963.) Selleck, G. W. 1961. Recent advances in the chemical control of wild oats. Weeds 9 : 60-7 1 . Selleck, G. W., and L. H. Hannah 1963. A review of 1962 field results with di-allate and tri-allate in the United States and Canada. Proc. 6th Brit. Weed Control Conf., pp. 361-67. Sexsmith, J. J. 1959. Effect of "Carbyne" on wild oats and spring wheat. Res. Rept., National Weed Committee (Western Canada Section), pp. 55-56. [28] Thurston, J. M. 1961. The effect of depth of burying and frequency of cultivation on survival and germination of seeds of wild oats (Avena fatua L. and Avena ludoviciana Dur.). Weed Res. 1:19-31. Thurston, J. M. 1962. The effect of competition from cereal crops on the germination and growth of A vena fatua L. in a naturally infested field. Weed Res. 2: 192-207. LITERATURE CITED Canada Department of Agriculture 1 959. Cultural control of wild oats. Public. 1044. 1 4 pp. Duncan, D. B. 1955. Multiple range and multiple F tests. Biometrics 11: 1-42. Evans, S. A. 1962. The control of Avena fatua (wild oats) in spring cereals with di-allate, tri- allate and barban. Proc. 6th Brit. Weed Control Conf. pp. 297-320. (Also in Weed Abstr. 12(3) :633. 1963.) Faivre-Dupaigre, R. 1963. Essais de destruction de la folle-avoine {Avena fatua L.) dans les cultures d'orge de printemps. Weed Res. 3:79-97. Foy, C. L. \96\a. Use of chemicals for wild oat control. Agrichem. West. Sept., pp. 7-8, 21. 19616. Uptake of radioactive 4-chloro-2-butynyl N-(3-chlorophenyl) carbamate (barbane) and translocation of C 14 in Hordeum vulgare and Avena spp. Res. Prog. Rept., West. Weed Control Conf., pp. 96-97. Friesen, G., and R. C. Henne 1962. The effect of 'Avadex' vapours on wild oat seeds. Proc. 9th Ann. Meeting Agri. Pest Tech. Soc, Ottawa, pp. 5-10. Friesen, H. A., J. D. Banting, and D. R. Walker 1962. The effect of placement and concentration of 2,3-DCDT on the selective control of wild oats in wheat. Canad. Jour. Plant Sci. 42:91-104. Holmes, H. M., and R. K. Pfeiffer 1962. Some aspects of the use of barban for wild oat control in winter wheat. Weed Res. 2:110-21. HOLROYD, J. 1964. Field investigations concerning the selective phytotoxicity of di-allate to Avena spp. in wheat and barley. Weed Res. 4: 142-66. Little, T. M., and Hills, F. J. 1963. Experimental methods for extension workers. Special publication of the Uni- versity of California Agricultural Extension Service. 1 12 pp. Parker, C. 1 963. Factors affecting the selectivity of 2,3-dichloroallyl-diisopropylthiolcarbamate (di-allate) against Avena spp. in wheat and barley. Weed Res. 3:259-76. Pfeiffer, R. K., and Holmes, H. M. 1961. A study of competition between barley and oats as influenced by barley seed rate, nitrogen level and barban treatment. Weed Res. 1:5-18. r 29 1 To simplify this information, it is sometimes necessary to use trade names of products or equipment. No endorsement of named products is intended nor is criticism implied of similar products not mentioned. 12im-ll,'66(G4463)P.A.V. ME! A FARM product; Well, not exactly— you can't grow auto- mobiles on farms, but farm products are essential in manufacturing them. Consider the annual agricultural needs of just one major automobile company. or, in terms of approximate acreage: 900,000 bushels of corn 736,000 bushels of flax- seed 74,000 bales of cotton 15,000 acres of corn 80,000 acres of flax 78,000 acres of cotton During the same period this company used products derived from 364,000 sheep and 36,000 cattle— plus many other items such as hog bristles and beeswax. In all, produce equivalent to the output of 1,000 good-sized farms is needed yearly. No wonder a top executive in the automotive industry has said: "Our plants, here and throughout the world, would have to close their doors in a few days if their flow of agricultural materials were to stop." Supplying America's countless industries— and feeding the nation bountifully— makes agriculture America's biggest and perhaps most important business. That is one reason why anything which affects agriculture affects everybody.