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.

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.

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 amount of free, unaltered (2,4-dichlorophenoxy) acetic acid (2,4-D) in resistant and susceptible plant species 1, 4, and 8 days after treatment was determined by three procedures. Centrifugation and chromatography of plant homogenates was a more reliable assay than trichloroacetic acid (TCA) precipitation or dialysis procedures. The foliar penetration of 14C-2-4-D and radioactivity which moved from roots into the growth media following foliar application of 14C-2,4-D varied from one plant species to another, but no general correlations with 2,4-D resistance was observed. The resistant burcucumber (Sicyos angulatus L.) and oats (Avena sativa L.) were not fatally injured primarily because unaltered 2,4-D was immobilized in the treated leaves and unaltered, free 2,4-D was reduced to nontoxic concentrations. The 2,4-D in susceptible cocklebur (Xanthium sp.) remained largely as free and mobile 2,4-D, and the treated plants were near death 8 days after treatment.

The effects of time, concentration, pH, temperature, and metabolic inhibitors on 4-amino-3,5,6-trichloropicolinic acid (picloram) uptake from nutrient solution by oats (Avena sativa L. ‘Markton’) and soybeans (Glycine max L. ‘Lee’) were studied. Oats and soybeans had similar absorption patterns of rapid initial uptake. However, total accumulation patterns markedly differed in that accumulation was concentration-dependent for oats but not for soybeans. Initial uptake by oats and soybean roots increased as solution concentration increased. Picloram was redistributed in oats and soybeans and some egress from roots to solution occurred. Picloram uptake by both plant species was markedly diminished with an increase in pH from 3.5 to 4.5, but pH had little effect from 4.5 to 9.5. Less picloram was taken up by oats and soybean roots from solution maintained at 4 C than at 26 C. Translocation to tops followed a similar trend. Increasing concentrations of three metabolic inhibitors, 2,4-dinitrophenol (DNP), sodium azide, and sodium arsenite, reduced root uptake of picloram in both species. All inhibitors (except DNP for oats) at 10−6 to 10−5 molar concentrations stimulated translocation of picloram to oats and soybean tops while higher concentrations depressed translocation.

Toxicity of soil-applied 2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine (terbutryn) to cucumbers (Cucumis sativus L. ‘Gemni’) and oats (Avena sativus L. ‘Nodaway’) was increased 2.2 times when the light intensity was raised from 11,000 to 22,000 lumens/m2 and 1.5 times when the moisture level was raised from low (25 to 50% field capacity) to high (75 to 100% field capacity). When the temperature was raised from the low level (19 C day, 14 C night) to the high level (29 C day, 24 C night) toxicity of terbutryn to oats was increased 1.6 times and toxicity to cucumber was increased 1.3 times. Analysis of interactions of the three variables on toxicity of terbutryn showed that environmental conditions favoring rapid growth resulted in an increase in phytotoxicity.

Studies were made of isozyme patterns of three enzymes and of total soluble proteins from seedlings of three crop species which were grown in association with different weed species. The gel electrofocusing separation technique was used. Marked qualitative and quantitative changes were observed in peroxidase of cabbage (Brassica oleracea L.) seedlings when grown in association with jimsonweed (Datura stramonium L.), velvetleaf (Abutilon theophrasti Medic.), wild mustard (Brassica kaber DC.), and green foxtail (Setaria viridis (L.) Beauv.). No differences were observed when lettuce (Lactuca sativa L.) and tomato (Lycopersicum esculentum Mill.) were grown in association with the above weed species. No differences were found in total soluble proteins or the isozyme patterns of esterase and acid phosphatase.

Herbicide treatments of 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron), 2,4-bis(isopropylamino)-6-(methylthio-s-triazine (prometryne), or methyl ester of 3-amino-2,5-dichlorobenzoate (chloramben ester) were applied preemergence to soybean (Glycine max (L.) Merr. ‘Dare’ or ‘Bragg’) plots previously treated with S-propyl dipropylthiocarbamate (vernolate), α,α.α,-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), or 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin). Sequential treatments of vernolate with linuron, prometryne, or chloramben ester controlled weeds more effectively in soybeans than did trifluralin or nitralin applied with the same preemergence treatments. Soybean injury was not severe enough to reduce seed yields in any year. Yields were greater in 1970 when soybeans were treated with vernolate than when treated with either trifluralin or nitralin. Soybean yields also were greater in 1970 when treated with chloramben ester than when treated with linuron or prometryne. In 1969 when soybeans were planted in a sandy loam, prometryne reduced stands more than did linuron or chloramben ester.

A simple, inexpensive, and versatile tractor-mounted spray system will allow spray application to be made to approximately six 6.1-m plots per minute under continuous operation.