Monosodium methanearsonate (MSMA) and arsenic acid (AA) were measured simultaneously in johnsongrass (Sorghum halepense (L.) Pers.) and cottonseed (Gossypium hirsutum L. ‘SJ-1’) by a bicolorimetric method. Tissues from plants sprayed with MSMA while growing and tissues with MSMA and AA added just prior to extraction were analyzed. Johnsongrass sprayed with MSMA solution at 11.2 kg/ha contained, on a dry weight basis, 423.0 ppmw of MSMA and 0.00 ppmw of AA at 7 days and 10.83 and 0.21 ppmw, respectively, after 54 days of regrowth. The cotton plants were sprayed twice to runoff with MSMA, first with 0.3 g/L and second with 1.2 g/L. Cottonseed from the sprayed cotton plants contained, on a dry weight basis, 2.45 ppmw of MSMA and 0.08 ppmw of AA after the first picking and 3.02 and 0.10 ppmw, respectively, after the second. Background levels of MSMA and AA were, respectively, on a dry weight basis, 0.63 and 0.02 ppmw in johnsongrass and 0.58 and 0.00 ppmw in cottonseed.

Gamma radiation of 3 megarads was applied to undiluted commercial formulations and aqueous solutions of 3-(3,4 dichlorophenyl)-1,1-dimethylurea (diuron), 1,1-dimethyl-(3-a,a,a-trifluoro-m-tolyl)-urea fluometuron), N,N-dimethyl-2,2-diphenylacetamide (diphenamid), 2,4-bis (isopropylamino)-6-(methylthio)-s-triazine (prometryne), dimethyl tetrachloroterephthalate (DCPA), a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) and sodium chlorate. The effect of radiation on herbicidal activity was assessed with bioassays. Radiation did not affect the bioactivity of undiluted or 50% solutions of any of the tested herbicides but decreased appreciably the activity of 100-ppm solutions of fluometuron, diphenamid, and prometryne. Diluted 100 and 10-ppm solutions of trifluralin lost part of their activity during storage in plastic containers and, in addition, following irradiation. It was not clear whether the decrease in activity observed in the 100-ppm solution of diuron was due to irradiation or to storage. No reduction in bioactivity was produced following irradiation of 100 and 10-ppm solutions of DCPA or 1% and 10% solutions of sodium chlorate.

In preliminary greenhouse evaluations and then in field studies, common cocklebur (Xanthium pensylvanicum Wallr.) and wild common sunflower (Helianthus annuus L.) were controlled by early postemergence applications of 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil). Bromoxynil on young soybeans [Glycine max (L.) Merr.] caused temporary necrosis, retarded growth, and delayed maturity but did not reduce the stand of soybeans. Subsequent recovery and final yields of treated soybeans were such that selective control of common cocklebur and wild common sunflower appeared feasible. Treatments were applied as aqueous sprays over the tops of both the weeds and the crop. Rates of 140 or 196 g/ha were sufficient to control common cocklebur or wild common sunflower that was in the six true-leaf stage or smaller. In terms of soybean development, the optimum time for treatment appeared to be about the first trifoliolate stage.

Tomato (Lycopersicon esculentum Mill. ‘Fireball’), white bean (Phaseolus vulgaris L. ‘Seaway’), and tobacco (Nicotiana tabacum L. ‘Delhi 34’ and ‘White Gold’) were pretreated with herbicides at one of three rates prior to fumigation with ozone at 0, 7.5, 15, or 30 pphm (parts per hundred million) for two 1.5-hr period. The plants were harvested 5 to 7 days after ozone fumigation, dried, and weighed. The natural logarithms of the dry weight data were subjected to multiple regression analysis to test for synergistic or antagonistic interactions between ozone and the various herbicides. Synergistic phytotoxicity was definitely observed for pebulate (S-propyl butylethylthiocarbamate) and possibly for chloramben (3-amino-2,5-dichlorobenzoic acid) in combination with ozone on tobacco ‘White Gold’ and ‘Delhi 34’, respectively. For most of the other combinations (chloramben, trifluralin α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) or monolinuron (3-(p-chlorophenyl)-1-methoxy-1-methylurea) on white bean, diphenamid (N,N-dimethyl-2,2-diphenylacetamide) or trifluralin on tomato, chloramben on tobacco ‘White Gold’, and pebulate on tobacco ‘Delhi 34’) the phytotoxicity in the presence of ozone was additive and no interaction was indicated. An antagonistic interaction between ozone and benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) was indicated on the two cultivars of tobacco.

The effect of 3,6-dichloro-o-anisic acid (dicamba) on common purslane (Portulaca oleracea L.) was studied under growth room conditions. Common purslane was quite sensitive to dicamba. The lethal rate depended on the age of the plants and increased with their development. The visual responses included bending of young stems, epinasty of leaves, and inhibition of nyctinasty, followed by necrosis of leaves, defoliation, swelling of stems, and death of the growing tips with loss of apical dominance. Stem elongation was inhibited and fresh weight of tops was markedly reduced by dicamba application to either the roots or foliage. Carboxyl-labeled dicamba-7-14C was absorbed slowly by common purslane leaves. However, translocation appeared rapid, with accumulation of dicamba observed in the young tissues. A small amount of dicamba was exuded through the roots. There was no indication of dicamba degradation in common purslane during 8 days following treatment.

The amount of lipid present on leaves of Canada thistle (Cirsium arvense (L.) Scop.) varied due to ecotype, site where grown, and date of sampling. Thistles from a site with the greatest wind movement and greatest evaporation produced the most lipid per unit area of leaf. The relative lipid yield of ecotypes was similar at different locations. Deposition of lipid on the leaves of Canada thistle increased from the early bud stage to the first bloom and late bloom stages of growth. The amount of lipid on the leaves and previous data on the response of these ecotypes to (2,4-dichlorophenoxy) acetic acid (2,4-D) were highly correlated. Three ecotypes with the most lipid were most resistant and four ecotypes with the least lipid were most susceptible to 2,4-D spray. Two ecotypes were inconsistent in that comparison.

Analysis of soil samples taken periodically from field plots on Dundee silty clay loam treated with single or dual annual applications of 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin) or α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) at 0.84 or 1.68 kg/ha indicated dissipation of the herbicides to a low residual level within 3 to 4 months following each application. No accumulation was noted with either herbicide regardless of frequency or rate of application. Nitralin phytotoxicity to sorghum (Sorghum bicolor L. ‘Dekalb 57E’) decreased more rapidly in soil that had received prior treatment with nitralin than in soil with no previous treatment. A microbiological influence is suggested because this effect was nullified by autoclaving the soil prior to herbicide treatment. This effect was not apparent with trifluralin. A survey of 250 fields indicated a significant, inverse correlation between nitralin and trifluralin residue level and soil pH. Nitralin persistence was greater in acid than in neutral soil.

The herbicide mixture 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) + 2-chloro-N-isopropylacetanilide (propachlor) was applied preemergence broadcast and in band widths of 18, 36, and 53-cm to corn (Zea mays L.). All herbicide treatments were applied as 1.1 kg of atrazine + 2.7 kg of propachlor per treated hectare. One row-middle cultivation and one rotary hoeing were also imposed on the herbicide treatments as variables. The 18-cm band of atrazine + propachlor with supplementary cultivation was as effective in controlling weed growth and maintaining corn yield as were wider herbicide bands or a broadcast treatment. Broadcast treated corn without row-middle cultivation produced significantly less grain than the handweeded check both years of the experiment. The average ratio of weed dry weight to reduction in corn yield was 0.8 to 1. Cultivation of row middles reduced average end-of-season weed yields 80%. Cultivator effectiveness on an 18-cm herbicide band equalled that measured on wider herbicide bands. Rotary hoeing reduced early season weed yields 82 and 38% in 1970 and 1971, respectively.

Varying concentrations of benzyladenine (BA), indoleacetic acid (IAA), gibberellic acid (GA), abscisic acid (ABA), and 2-chloroethylphosphonic acid (ethephon) were used to induce sprouting of dormant purple nutsedge (Cyperus rotundus L.) tubers. BA at 50 to 300 ppm stimulated sprouting. The continuous presence of BA during the sprouting period was necessary to give significant sprout stimulation. Neither IAA at 1, 10, or 100 ppm; GA at 10, 100, or 1000 ppm; nor ethephon at 10, 100, or 1000 ppm had stimulatory effects on sprouting. ABA counteracted the stimulatory effects of BA when tubers were treated with ABA following BA treatment. Sprouting was markedly greater at 33 C day, 25 C night than at 24 C day, 17 C night. Growth of plants originating from tubers pretreated with 100 ppm BA did not differ significantly from the controls. Sustained BA applications at 100 and 200 ppm produced numerous plants with tuft-type growth habit, delayed flowering, and reduced the number of inflorescences. Numerous short, diageotropic rhizomes were produced.

The effects of twelve substituted dinitroaniline herbicides on soybeans [Glycine max (L.) Merr., ‘Corsoy’], velvetleaf (Abutilon theophrasti Medic.), and giant foxtail (Setaria faberi Herrm.) were evaluated under field conditions in 1971 and 1972; and the relative persistence of herbicide residues in soil was determined by field bioassay. Of the herbicides tested, dinitramine (N 4,N 4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine), trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), and benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2, 6-dinitro-p-toluidine) reduced soybean stands in 1971. Only dinitramine reduced soybean stands in 1972 when applied in low rates, but all of the herbicides except CGA-10832 (N,N-propyl-N-cyclopropylmethyl-4-trifluoromethyl-2,6-dinitroaniline) and chlornidine [N,N(2-chloroethyl)-2,6-dinitro-4-methylaniline] reduced soybean stands at high rates. Overall, oryzalin (3,5-dinitro-N 4,N 4-dipropylsulfanilamide), dinitramine, and BAS-3921 H[N-propyl-N-(2-chloroethyl)-2,6-dinitro-4-trifluoromethylaniline] provided the best velvetleaf control; while trifluralin, benefin, CGA-10832, and BAS-3921 H produced the most satisfactory giant foxtail control. In 1972, residues of seven of the herbicides caused injury to oats planted over the plot area 355 days after the original herbicide application. The greatest oat injury was caused by trifluralin and oryzalin. Oats were not injured, however, from dinitramine residues when planted only 75 days after the herbicide application.

Growth response of five species of soil algae to 4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5 (4H)one (metribuzin) and its 6-isopropyl and 6-cyclohexyl analogs were studied in vitro. Species of Chlorella, Chlorococcum, Chlamydomonas, and Anabaena were exposed to 0.05, 0.1, 0.5, and 1.0 ppm (w/v) of the herbicides in liquid nutrient, while a species of Schizothrix was studied at the same levels in soil culture. With one exception, the growth and numbers of all of the algae were significantly reduced by increasing herbicide concentrations. Anabaena was not affected by 0.05 ppm of the cyclohexyl analog. No growth was permitted by any of the herbicides at 1.0 ppm. Chlorella and Chlamydomonas could not grow in the presence of 0.5 ppm of metribuzin or the cyclohexyl analog. Differences in response to the triazinones were noted between species. Chlamydomonas was the most sensitive and Anabaena and Chlorella the most resistant.

The root growth rate index of velvetleaf (Abutilon theophrasti Medic.) was significantly greater than that of five other weed species. The root growth rate index of sorghum [Sorghum bicolor (L.) Moench ‘RS-626’] was found to be significantly higher than that of soybeans [Glycine max (L.) Merr. ‘Ford’]. Shoot growth rate indexes of three perennial broadleaf species studied were significantly lower than shoot growth rate indexes of six annual species. Root weights of perennial broadleaf species were not significantly different from root weights of velvetleaf and soybeans. Soybeans were found to have a significantly higher shoot to root ratio than seven weed species but not higher than sorghum. All other species had larger leaf weights and leaf areas than the three broadleaf perennials. While there were significant differences in leaf weights among six species, there were no significant differences in leaf area. Seed weight was not significantly correlated with emergence rate index and root weight but was correlated to all other factors studied. Emergence rate index was correlated with root growth rate index but not with shoot growth rate index.

The fungicide, Dyrene [2,4-dichloro-6-(o-chloroanilino)-s-triazine], severely injured var. mite of Canada thistle [Cirsium arvense (L.) Scop.]; and the damage resembled that caused by bipyridylium herbicides. Regrowth from treated plants was abnormal. Other arylamino-s-triazines were from slightly to severely phytotoxic to leaf sections of the var. mite. The var. horridum of Canada thistle was not affected by Dyrene or related compounds. Dyrene and metabolites of Dyrene which were phytotoxic to var. mite leaf disks in bioassay tests were isolated from treated var. mite and horridum plants, but none of these compounds injured the var. horridum. One metabolite was found only in the var. mite; the other five occurred in both varieties. The metabolites were apparently formed from Dyrene by conjugation reactions.

The relative phytotoxicities of 12 substituted dinitroaniline herbicides to soybeans [Glycine max (L.) Merr ‘Corsoy’], velvetleaf (Abutilon theophrasti Medic.), and either giant foxtail (Setaria faberi Herrm.) or foxtail millet [Setaria italica (L.) Beauv.] were compared under greenhouse and laboratory conditions. In these studies, dinitramine (N 4,N 4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) was most toxic to each species. Dinitramine, trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), and BAS-3921 H [N-propyl-N-(2-chloroethyl)-α,α,α-trifluoro-2,6-dinitro-p-toluidine] were most inhibitory of soybean shoot growth, while oryzalin (3,5-dinitro-N 4,N 4-dipropyl-sulfanilamide), dinitramine, and BAS-3921 H were most inhibitory of root growth. Similarly, dinitramine, oryzalin, nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], and BAS-3921 H inhibited velvetleaf shoot growth; and oryzalin, dinitramine, chlornidine [2,6-dinitro-N,N-di(2-dichloroethyl)-p-toluidine], nitralin, and GS-39985 (N-n-propyl-N-tetrahydrofurfuryl-4-trifluoromethyl-2,6-dinitroaniline) reduced root growth. All of the herbicides except oryzalin and nitralin inhibited foxtail millet shoot growth, while all of the herbicides reduced root growth.

The effects on leucine uptake and its incorporation into protein by cucumber (Cucumis sativus L. ‘Ashley’) cotyledon tissue following treatments with 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne) were determined. Prometryne decreased 14C-leucine uptake both in the light and in the dark. Prometryne decreased leucine incorporation into protein only when the discs were also exposed to over 4 hr of light. Percent of absorbed leucine incorporated into protein was increased by a 4 hr exposure in the light to 10−4M prometryne following a 24-hr dark exposure to this same concentration. Similar exposure to 10~5M prometryne had no effect. Percent of leucine incorporated into protein was decreased by 10-5M prometryne following a 24 hr exposure to this same concentration in the light. However, under these conditions 10−4M prometryne had no effect. It is speculated that the increased percentage of leucine incorporated into protein may be related to increased availability of the absorbed leucine for use in protein synthesis rather than an effect of the herbicide on the rate of protein synthesis

When the mixture of 3.4 kg/ha of S-ethyl N-ethylthiocyclohexanecarbamate (cycloate) plus 1.1 kg/ha of 3′-hydroxypropionanilide isopropylcarbamate (R 11913) was applied to three soils before planting sugarbeets (Beta vulgaris L.), the average stand of kochia (Kochia scoparia (L.) Schrad.) was reduced by 89% as compared to 9% with the standard rate of 4.5 kg/ha of cycloate. The competition of foxtail millet (Setaria italica (L.) Beauv.), redroot pigweed (Amaranthus retroflexus L.), and kochia was nearly eliminated throughout the growing season by a combination of 3.4 kg/ha of cycloate plus 1.1 kg/ha of R 11913 applied preplanting and 0.84 kg/ha of methyl m-hydroxycarbanilate m-methylcarbanilate (phenmedipham) applied postemergence. This combination of treatments minimized competition from weeds all season, and the yield of sucrose was within 8% of that of the handweeded plots. Residues of the mixture of cycloate plus R 11913 were not detected biologically in two soils 8 months following application.

Sprayed aqueous emulsions of long chain amine salts of (2,4-dichlorophenoxy)acetic acid (2,4-D) penetrated faster into sunflower (Helianthus annuus L. ‘Peredovik’) leaves than did sprayed dimethylamine salt aqueous emulsions at 21 C and 5% relative humidity (RH). The initial absorption (65 to 70% in 13 hr) was independent of light, but the following much slower absorption was strongly light dependent. The long-chain amine salts sprayed in diesel oil as carrier were 90% absorbed in 4 hr. It was concluded that long chain amine salts should be sprayed in this carrier to facilitate penetration into leaves and to reduce possible environmental contamination.

In growth room studies, N,N-diallyl-2,2-dichloroacetamide (hereafter referred to as R-25788) was the most effective of three antidotes for the reduction of EPTC (S-ethyl dipropylthiocarbamate) injury to corn (Zea mays L. ‘United Hybrid 106’). R-25788 reduced EPTC injury to corn as a seed treatment, as an incorporated soil spray, or in nutrient solution in quartz sand nutrient culture. CDAA (N,N-diallyl-2-chloroacetamide) was also an EPTC antidote for corn when applied to the soil or in nutrient solution but was itself toxic to corn when applied as a seed treatment. The antidote 1,8-naphthalic anhydride (hereafter referred to as naphthalic anhydride) was less effective than R-25788 as a seed treatment and was ineffective when applied to the soil. Naphthalic anhydride was the only one of the three antidotes which also reduced EPTC toxicity to green foxtail [Setaria viridis (L.) Beauv.].

Dicamba (3,6-dichloro-o-anisic acid) dissipated in 4 weeks and in 9 to 16 weeks when sprayed on grassland soils of Texas at 0.28 kg/ha and 0.56 kg/ha, respectively. At three of four locations ranging from humid to semiarid and from clay to sandy loam and sampled from 9 to 63 weeks after treatment, usually residues were no deeper than 120 cm and never deeper than 150 cm. However, dicamba residues were detected 120 cm deep 53 weeks after application of granules at 1.68 or 2.24 kg/ha to sand of semiarid grassland. Since dicamba sprays are usually applied at 0.56 kg/ha or less for grassland restoration in Texas, it is unlikely that residues of dicamba will persist in soil through the growing season from spring applications.

Various soybean [Glycine max (L.) Merr. ‘Amsoy’] losses during harvesting with a combine were studied in relation to different weed densities, weed species, and growing weeds (early harvest) versus desiccated weeds (late harvest). Average soybean losses from shattering and stubble, stalk, and threshing losses were 7.8, 0.9, 2.0, and 1.4% of total yields, respectively. All harvest losses except threshing losses were significantly greater on late as compared with early harvested soybeans. The major loss from weeds in soybeans was reduced yields due to competition; whereas, harvesting losses were associated with high soybean yields and low weed yields. Soybean harvesting losses were 19% greater on plots containing a predominance of broadleaf compared with grass weeds. Average harvesting losses of 12.1% of total soybean yields ranged with treatments from 8.8 to 15.5%. Average gathering losses were 10.7% and threshing losses 1.4% of total soybean yields.