The dinitroaniline herbicides, trifluralin and pendimethalin, are applied to approximately 90% of land seeded to cotton on the Texas Southern High Plains. Trifluralin and pendimethalin at 0.6 and 1.1 kg ai/ha were applied annually to plots from 1983 through 1994. Cotton stand counts, lint yield, and fiber quality varied from year-to-year due to environmental conditions. Differences in lint yield or fiber quality over the 11-yr period were not related to herbicide applications.

The relationship between herbicide injury and soybean [Glycine max (L.) Merr. ‘Amsoy 71’] yield response was studied under weed free conditions at three locations. Reduced crop vigor at early growth stages was not an adequate indicator of yield response. Yield reduction was greater when soybean stand was reduced by herbicides than when stand was reduced to the same level by hand thinning. Yield response was a function of the degree and persistence of crop vigor reduction in a reduced stand of soybeans.

A 2-yr field study was conducted to determine effects of posttreatment irrigation timing on pendimethalin efficacy and dissipation in turfgrass. Factors investigated included herbicide rate, formulation, and the interval between pendimethalin application and the initial posttreatment irrigation. Plots received an initial posttreatment irrigation of 1.25 cm 0, 7, 14, 21, and 28 d after treatment. Pendimethalin efficacy on smooth crabgrass was evaluated, and turfgrass foliage and the upper 2.5-cm layer of soil were periodically assayed for pendimethalin residues. Pendimethalin 1.71% granular provided better weed control than pendimethalin 60% wettable powder at all rates, irrigation events, and years. Efficacy of granular pendimethalin was not affected by a delay in posttreatment irrigation, whereas efficacy of pendimethalin in the wettable powder formulation was reduced when irrigation was applied later than the day of treatment. Chromatographic analyses indicated that an average of 54% of the applied pendimethalin (wettable powder formulation) was retained on turfgrass foliage immediately after treatment, compared to 9% for the granular formulation. Soil residue analyses confirmed that a greater proportion of applied pendimethalin reached the soil surface immediately after treatment in the granular formulation than in the wettable power formulation.

Absorption and translocation of 14C-ethalfluralin (N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine) were measured in cucumber plants in the field and greenhouse. In field enclosures, cucumbers treated with 1.68 or 3.36 kg ai/ha preemergence soil-surface applications of 14C-ethalfluralin accumulated significantly more 14C in leaves than in petioles, stems, or fruits. In greenhouse studies, 14C-ethalfluralin vapor was absorbed by both cucumber seedling stems and cotyledons. Seedlings absorbed 14C-ethalfluralin from a nutrient solution and translocated 14C into all plant parts. Cucumber absorbed 14C-ethalfluralin topically applied to the stem and translocated 14C acropetally, while only limited basipetal translocation occurred. Although cotyledons absorbed 14C-ethalfluralin, very little 14 C moved out of the treated tissue.

In greenhouse studies, soil organic matter reduced the herbicidal activity of ethalfluralin (N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine). Fifty percent inhibition (I5.0) values for barnyardgrass [Echinochloa crus-galli (L.) Beauv.] stand, injury, and shoot fresh weight increased as the soil organic-matter level increased. No difference in ethalfluralin tolerance was found among 16 cucumber (Cucumis sativus L.) cultivars. When grouped according to market type, fresh market cultivars tended to be injured more than pickling cultivars by excess ethalfluralin. Both shoots and roots of cucumber absorbed the herbicide, but exposure of roots to ethalfluralin was more toxic than exposure of shoots. Field studies indicated that with certain edaphic and environmental conditions, cucumbers can be injured by preemergence applications of ethalfluralin. Injury was greatest in a low organic-matter soil following a heavy rain. Ethalfluralin at 1.3 kg/ha gave adequate weed control in 1 and 3% organic-matter soils, but not in a 9% organic-matter soil.

A sprinkler system was developed that applied water to quadrant-shaped plots with a uniformity coefficient greater than 90% for any 2-m zone between 3 and 9 m from sprinklers that were located at the vertex of the quadrant. With this sprinkler system, many variables that affect the performance and behavior of herbicides applied in irrigation water can be studied. When applied through this sprinkler system in 1.4 cm of water, alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] at 3.3 kg/ha, EPTC (S-ethyl dipropylthiocarbamate) at 3.3 kg/ha, EPTC + trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 3.3 + 0.6 kg/ha, and EPTC + oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) at 3.3 + 0.8 kg/ha controlled barnyardgrass [Echinochloa crus-galli (L.) Beauv.], common lambsquarters (Chenopodium album L.), and hairy nightshade (Solanum sarachoides Sendt.) selectively in beans (Phaseolus vulgaris L. ‘Pinto 114’).

The resistance of four populations of slender foxtail from England to chlorotoluron, pendimethalin, and the methyl ester of diclofop was studied in whole-plant spray assays. Two populations showed cross-resistance to all three herbicides while a third showed resistance to chlorotoluron only. Resistance, although not absolute, was sufficient to cause substantial reductions in herbicide performance at recommended field doses. Resistant (Peldon) and susceptible (Rothamsted) populations also were assessed for resistance to six dinitroaniline herbicides in a petri dish test in which the effects on shoot development were measured. The degree of resistance of the Peldon population varied considerably among herbicides, with greatest resistance to pendimethalin, whereas sensitivity to ethalfluralin, isopropalin, and trifluralin was similar to that of the Rothamsted standard. Differential response to butralin and oryzalin was smaller than to pendimethalin. The large difference between populations in their response to pendimethalin and trifluralin was confirmed in a pot experiment.

In field experiments at Prosser, WA, black nightshade (Solanum nigrum L. # SOLNI), eastern black nightshade (S. ptycanthum Dun. # SOLPT), American black nightshade (S. americanum Mill. # SOLAM), hairy nightshade (S. sarrachoides Sendtner # SOLSA), and sometimes accessions within a species responded differentially to herbicides applied preplant incorporated, preemergence, or postemergence. Also, the response of the nightshades to some of the herbicides varied significantly between years. Generally, black nightshade was more tolerant of herbicides than were the other three species. An accession of black nightshade from England and an accession of eastern black nightshade from Minnesota were the most tolerant of herbicides of eight accessions evaluated. Of the 25 herbicides evaluated, preplant-incorporated applications of ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl) benzenamine] and preemergence applications of alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide], chloramben (3-amino-2,5-dichlorobenzoic acid), lactofen [1′-(carboethoxy)ethyl 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoate], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl] acetamide] controlled all species best. These herbicides reduced the oven-dry weights of both accessions of all four species of nightshades by 93% or more. Nightshades varied widely in their response to the thiocarbamates.

Plasmodium falciparum merozoites have an array of 2–3 subpellicular microtubules, designated f-MAST. We have previously shown that colchicine inhibits merozoite invasion of erythrocytes, indicating a microtubular involvement in this process. Colchicine inhibition of invasion was reduced by the Taxol®-stabilization of merozoite microtubules prior to colchicine exposure. Immunofluorescence assays showed that the number and length of f-MASTs were reduced in colchicine-treated merozoites, confirming that microtubules were the target of colchicine inhibition. The dinitroaniline drugs, trifluralin and pendimethalin, were shown by immunofluorescence to depolymerize the f-MAST and both drugs were inhibitory in invasion assays. These results demonstrate that the integrity of the f-MAST is important for successful invasion. Fluorescence imaging demonstrated the alignment of mitochondria to f-MAST, suggesting that mitochondrial transport might be perturbed in merozoites with disorganized f-MAST. Depolymerizing mt in late-stage schizonts did not affect the allocation of mitochondria to merozoites.