A mixture of activated carbon and vermiculite was used to increase the tolerance to 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) of direct-seeded cucumbers (Cucumis sativus L., var. Wisconsin SMR-15) in greenhouse tests and direct-seeded tomatoes (Lycopersicum esculentum Mill, var. Bouncer) in greenhouse and field (var. Heinz 1370) tests. The tolerance of cucumbers to dimethyl tetrachloroterephthalate (DCPA) and 4-(methylsulfonyl)-2,6-dini tro-N,N-dipropylaniline (nitralin) also was increased in field trials. When the mixture was placed in a hole (0.75 inch deep by 1 inch diam) over the crop seed to the level of the soil surface, preemergence herbicides were detoxified in the small area; and the crop plant was not injured. The herbicide remained active outside the small protected area. Also, a wafer consisting of an activated carbon-vermiculite mixture, fertilizer, and seed provided protection to direct-seeded crops.

The effects of an approximate 1:4 commercial mixture of 4-amino-3,5,6-trichloropicolinic acid (picloram) and (2,4-dichlorophenoxy)acetic acid (2,4-D) on a natural population of soil algae were studied at dosages of 0.28, 0.56, and 1.12 kg/ha of picloram. No change in the composition of the algal flora was noted over an 18-month period, regardless of dosage. In vitro studies indicated that mixtures of picloram and 2,4-D inhibited growth of Chlorella vulgaris Beyer. at concentrations above 100 ppm, but concentrations above 250 ppm were needed for growth inhibition of Cylindrospermum licheniforme (Bory) Kuetz. or Chlorococcum sp. Picloram alone inhibited all three algae at 50 ppm, while 2,4-D produced no inhibitory effects at concentrations less than 400 ppm.

In greenhouse studies, lateral movement and toxicity of S-ethyl N-ethylthiocyclohexanecarbamate (cycloate) to barnyardgrass (Echinochloa crusgalli (L.) Beauv.) was greater in a loamy sand soil than in two silt loam soils when cycloate was applied by subsurface line injection. Greatest movement and effectiveness resulted from injection into a preirrigated soil without further irrigation. Lateral movement was adequate under furrow irrigation, but the treated band was displaced. Movement of the cycloate was inadequate under sprinkler or subirrigation. Cycloate was more effective when mechanically mixed with the soil than when injected. Cycloate moved more readily in moist soils than in dry soils. When cycloate was injected into a dry loamy sand soil, movement was similar whether irrigation was applied immediately or after 24 hr.

The conversion of 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) to N-chloro-4-phenyl-3(2H)-pyridazinone glucosamine (hereinafter referred to as N-glucosyl pyrazon) in intact seedlings and in leaf discs of red beets (Beta vulgaris L., var. Detroit Dark Red) was significantly greater in the light than in the dark. Pyrazon conjugation with glucose was dependent on the carbohydrate status of the leaf tissue, since the formation of the N-glucoside in the dark was further reduced with dark pretreatment but could be restored to the level observed in the light by infiltrating the leaf discs with supplemental sucrose.

Cacodylic acid (hydroxydimethylarsine oxide) was more phytotoxic than monsodium methanearsonate (MSMA), sodium arsenate, or sodium arsenite when foliarly-applied. MSMA was much more effective on dicotyledonous than on monocotyledonous species. Sodium arsenite and arsenate had little effect on grasses. A comparative study of absorption, transport, and metabolism in beans (Phaseolus vulgaris L. ‘Black Valentine’) revealed that cacodylic acid and MSMA were transported about equally from the leaves to the terminal bud and expanding leaves whereas negligible amounts of sodium arsenite and arsenate were translocated. The latter two compounds caused more rapid contact injury to the treated leaves than either organic arsenical. There was no indication that cacodylic acid or MSMA was demethylated to form inorganic arsenicals or reduced to trivalent arsenic compounds. Studies with 14C-MSMA indicated that about 40% of the 14C and arsenic recovered was bound rapidly to another molecule to form a ninhydrin-positive complex. In small amounts, arsenate combined with some component of plant tissues. Also, arsenite probably was oxidized to arsenate. In beans, root-applied sodium arsenite was more phytotoxic than sodium arsenate and both were much more phytotoxic than cacodylic acid and MSMA. Most differences in phytotoxicity could not be explained by differences in rates of absorption by bean roots. Arsenite caused considerable contact injury to the root system, probably accounting for its relatively great phytotoxicity. Both cacodylic acid and MSMA were more phytotoxic per mole of tissue arsenic when foliarly-applied than when root-applied.

Downy brome (Bromus tectorum L.) seedling emergence was greatest from soil depths of 1 inch or less, but occasionally seedlings emerged from depths of 4 inches. Downy brome seed covered by soil germinated more rapidly than those seed on the soil surface. More downy brome seedlings emerged, and from greater depths, from coarse-textured soils than fine-textured soils when moisture was not limiting. Soil type did not influence longevity of downy brome seed buried in the soil. Most (98%) 8-month-old downy brome seed buried 8 inches in the soil germinated but did not emerge in 1 year; and none remained viable in the soil after 5 years. The moldboard plow was more effective in reducing downy brome populations than a sweep plow or one-way disk in a continuous winter wheat (Triticum aestivum L.) cropping system.

The use of 1,8-naphthalic anhydride, at 0.5% by corn (Zea mays L. ‘501D’) seed weight, eliminated most of the corn yield loss caused by S-ethyl dipropylthiocarbamate (EPTC) at 3.4, 6.7, or 10.0 kg/ha. The seed protectant partially reduced the moderate corn yield loss from S-ethyl diisobutylthiocarbamate (butylate) at 9.0 kg/ha. This seed protectant provides a new approach to increased weed control while maintaining selectivity in the production of corn.

Honey mesquite [Prosopis julifiora var. glandulosa (Torr.) Cockerell] and velvet mesquite [P. julifiora var. velutina (Woot.) Sarg.] seedlings were treated on individual leaves with 20 or 40 μg of (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), 4-amino-3,5,6-trichloropicolinic acid (picloram), or a 1:1 mixture thereof. Formulation of herbicides in a DMSO-complex carrier (dimethyl sulfoxide, ethylene glycol, phytobland oil, water: 50:25:15:10, v/v) enhanced activity considerably over that obtained with an aqueous carrier, the degree of enhancement being greater with 2,4,5-T than with picloram. Lack of major varietal differences in morphological or anatomical response suggests that observed varietal differences in sensitivity of field mesquite to aerial sprays are not a function of the variety itself, but are related to climatic or edaphic differences among sites which the varieties occupy.

Adsorption capacities of Walla Walla silt loam soil for 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) were determined after each extraction with ethyl ether, ethyl alcohol, and hot water. The results suggested that the ether and alcohol-extractable components of the soil organic matter, i.e. fats, oils, waxes, and resins, had a negligible capacity to adsorb atrazine but that hot-water-extractable materials, i.e. polysaccharides, had a small adsorptive capacity. of the compounds chosen to be representative of some soil organic matter components, polysaccharide types had low affinities, a protein and a nucleic acid had intermediate affinities, and humic acid, lignin, and quinizarin had high affinities for atrazine. Comparison of adsorption isotherms of atrazine to lignin and humic acid at 25 and 62 C suggested that a weak chemical bond may contribute to retention of the herbicide by soil organic matter. Nearly quantitative desorption of atrazine from native and calcium saturated soils was affected by repeated water extraction.

Compared to corn (Zea mays L.) (resistant), oats (Avena sativa L.) (susceptible), and giant foxtail (Setaria faberii Herrm.) (susceptible), fall panicum (Panicum dichotomiflorum Michx.) and large crabgrass (Digitaria sanguinalis (L.) Scop.) metabolized 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) at an intermediate rate. The order of tolerance of these five species (corn > fall panicum and large crabgrass > giant foxtail > oats) is identical to the order of their ability to metabolize atrazine. In 6 hr, corn, fall panicum, large crabgrass, giant foxtail, and oats metabolized 96, 44, 50, 17, and 2%, respectively, of the 14C-atrazine absorbed from a 10 ppm solution and translocated to the foliage, leaving concentrations of 2.2, 34.8, 30.1, 59.8, and 66.3 mμ moles, respectively, of atrazine per g of fresh weight of shoots. Hydroxyatrazine [2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine] was found in the shoots of corn and giant foxtail. Corn shoots also contained a more hydrophilic metabolite, presumably a peptide conjugate. Hydrophilic metabolites found in the shoots of giant foxtail, fall panicum, and large crabgrass were chromatographically identical to the hydrophilic metabolite found in corn.

The copper content of emersed parrotfeather (Myriophyllum brasiliense Camb.) roots ranged from 52 to 6,505 ppmw after root applications of copper sulfate pentahydrate (hereinafter referred to as CSP) at 0.25 to 16.0 ppmw of copper, respectively, under greenhouse conditions. The coefficient of correlation for copper in the treatment solution to the copper content of the roots was 0.9502. A slight acropetal movement of copper occurred because of an increase of CSP in solution and an increase in treatment time. Concentrations of CSP at 2.0 ppmw of copper or higher inhibited growth of parrotfeather. Phosphorus levels in the roots of parrotfeather were reduced by root applications of CSP at 1.0 ppmw of copper or higher during a 2-week treatment period.

MH (1,2-dihydro-3,6-pyridazinedione) was applied at 4 to 6 lb/A, in spring and fall, with and without (2,4-dichlorophenoxy)acetic acid (2,4-D), on roadsides normally mowed from 2 to 12 times a year. MH at 6 lb/A applied in spring generally reduced grass height. Lower rates and fall applications were generally ineffective. Depending on area, rural or urban, and retardant effectiveness, between zero and five mowings per year were saved. When the MH was effective and the turf was not strong and vigorous, annual weeds such as crabgrass (Digitaria spp. Heist.), foxtail (Setaria spp. Beauv.), and ragweed (Ambrosia spp. L.) often increased and gave the roadside an undesirable appearance. When MH was used without 2,4-D, the roadside generally had a poorer appearance than when not treated. When MH was applied with 2,4-D and no application ‘'skips” or annual weed infestation occurred, the roadside sometimes had a satisfactory appearance. The time when MH can be effectively applied is short (about 2 weeks). Rains, winds, and springtime roadway work make proper timing of applications difficult under Minnesota conditions. Applications of 2,4-D alone or with MH were effective in reducing roadside weeds.

Representative species of six genera of marine unicellular algae (Chlorococcum sp., Dicrateria inornata Parke, Dunaliella tertiolecta Butcher, Nannochloris sp., Isochrysis galbana Parke, and Monochrysis lutheri Droop) were treated in unialgal culture with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), 1-butyl-3-(3,4-dichlorophenyl)-1-methylurea (neburon), 3-(p-chlorophenyl)-1,1-dimethylurea (monuron), and 1,1-dimethyl-3-phenylurea (fenuron). Tests were conducted at salinities of 5, 10, 20, and 30 parts per thousand (ppt). The herbicides depressed concentration of carbohydrate in all species. Dunaliella tertiolecta was most resistant; its carbohydrate content decreased 9.2% at 5 ppt salinity and 17.9% at 30 ppt. Chlorococcum was most susceptible; its carbohydrate content decreased 49.1% at 5 ppt and 65.6% at 30 ppt salinity.

Paper chromatographic separation of hydroxydimethylarsine oxide (cacodylic acid), monosodium methanearsonate (MSMA), sodium arsenate, and sodium arsenite was achieved with the aid of four solvent systems. Aqueous extracts of plant tissues removed essentially all the arsenicals applied, but methanolic fractionation was required before the extracts could be analyzed by paper chromatographic procedures. A standard nitric-sulfuric acid digestion procedure was employed for arsenic analyses, but great care was taken to avoid sulfuric-acid-induced charring by first adding relatively large amounts of nitric acid to drive off chlorides present. Depending upon the amount of chloride present, substantial losses of arsenic as arsine chlorides were observed if the samples charred. Five minutes in fuming sulfuric acid to completely break the carbon-arsenic bonds was another critical requirement for the quantitative determination of arsenic from cacodylic acid and MSMA. The silver diethyldithiocarbamate colorimetric method was useful for detecting as little as 0.6 μg or as much as 20 μg of arsenic per sample.

Under furrow irrigation, control of field bindweed (Convolvulus arvensis L.) was at least 90% where 4.5 and 6.7 kg/ha of 3,6-dichloro-o-anisic acid (dicamba) had been applied 1 year before. Dicamba at 2.2 kg/ha, mixtures of dicamba and (2,4-dichlorophenoxy)acetic acid (2,4-D), and 2,4-D alone were less effective. No herbicide treatment had eradicated field bindweed after 3 years, but the combined use of herbicides, tillage, and crop competition had suppressed the growth of field bindweed by 31 to 55%. Sugarbeet (Beta vulgaris L.) seedlings appeared normal where 2,4-D had been applied 8 months earlier, but over 90% of the seedlings were killed in plots treated with dicamba. Treatment with 2.2 kg/ha of 2,4-D and dicamba, singly or in combination, resulted in yields of grain sorghum (Sorghum bicolor (L.) Moench) significantly greater than yields from the untreated field bindweed check. The 4.5 and 6.7-kg/ha rates of dicamba still affected sugarbeets during the second year following treatment. Corn (Zea mays L.) production was not affected in the third year by any herbicide treatment. Dicamba, applied at 2.2, 4.5, and 6.7 kg/ha, persisted in the upper 15 cm of top soil for at least 12 months in amounts that were phytotoxic to field beans (Phaseolus vulgaris L.) and sugarbeets.

The adsorption of picloram (4-amino-3,5,6-trichloropicolinic acid) was studied for several Canadian prairie soils and for various other adsorbents. The kd values for the soils ranged from 0.09 to 0.75 and were correlated only with soil organic matter. The kd values for other adsorbents varied from 0 to 232, the order of adsorption being activated charcoal > anion exchange resin > peat moss > cellulose triacetate. There was no adsorption of picloram on montmorillonite and kaolinite clays, cation exchange resin, wheat straw (Triticum aestivum L.), or cellulose powder. The differences in the adsorption of picloram were explained on the basis of the relative affinities of the various adsorptive surfaces for the molecular or the ionized forms of the acid.

Postemergence directed application of 0.56 kg/ha of 2,3,5-trichloro-4-pyridinol (pyriclor) gave control of witchweed (Striga lutea Lour.) equivalent to 2.24 kg/ha of (2,4-dichlorophenoxy)acetic acid (2,4-D) without injuring corn (Zea mays L.). Pyriclor applied to the soil surface or incorporated did not significantly injure tobacco (Nicotiana tabacum L.) at rates of 2.24 kg/ha and less. Peanut (Arachis hypogaea L.) was not injured by pyriclor incorporated in soil at 0.56 kg/ha; Irish potato (Solanum tuberosum L.) was slightly injured. Treatment with 0.56 kg/ha of pyriclor applied in the same manner killed six crop species and four weed species also included in the experiment. In 2 years of field experiments, application of pyriclor at 0.21 and 0.63 kg/ha to soil before transplanting, or these rates applied over the top of tobacco after transplanting, controlled large crabgrass (Digitaria sanguinalis L. Scop.) until maturity of the tobacco, and did not significantly reduce yield or cause permanent injury to the crop.

The phytotoxicity of 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) to corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) seedlings and 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) to soybean seedlings increased with increasing temperature from 20 to 30 C. The phytotoxicity of α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) did not change significantly between 20 and 30 C. Corn and soybean plants grown at 30 C translocated more 14C from 14C-atrazine and soybeans more 14C from 14C-linuron to the shoots during the 4-hr root uptake treatment period than plants grown at 20 C. There was less accumulation of 14C from 14C-atrazine in soybean roots and 14C-linuron and 14C-trifluralin in the roots of corn and soybean plants grown at 30 C compared to those grown at 20 C. Comparison of data at 30 C and 20 C during the 4-hr root uptake treatment period showed enhanced root to shoot movement of 14C from 14C-atrazine in corn and from 14C-linuron in soybean at the higher uptake treatment temperature indicating a possible relationship between increased herbicide transport to the shoot at high temperature and increased phytotoxicity.

Phytotoxicity of α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), incubated for 10 months in Sharpsburg silty clay loam at 0.8 field capacity, remained a 6.4, 0, and 1.6 ppmw of the original 8 ppmw at 15, 25, and 35 C, respectively. In Anselmo sandy loam after 10-months incubation, trifluralin phytotoxicity remained at 3.0, 3.2, and 0.6 ppmw of the original 4 ppmw at 15, 25, and 35 C, respectively. Breakdown of 14C-trifluralin to 14CO2 in both soils was more rapid at 1.6 field capacity than at 0.8 field capacity, and at 1 ppmw than at 100 ppmw of trifluralin. Breakdown of 14C-trifluralin to 14CO2 accounted for 5 and 3% of the decrease of 14C-activity in Sharpsburg silty clay loam and Anselmo sandy loam, respectively.