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.

AAL-toxin, produced by Alternaria alternata, was investigated for its phytotoxic effects on 86 crop and weed species. On susceptible tomato leaf discs, AAL-toxin caused electrolyte leakage and chlorosis at 0.01 μM in 24 h. Plants tested exhibited a range of response. AAL-toxin damaged sensitive plants at 5 μM while other plants showed minimal damage at > 1000 μM. Cotton and the important weeds, Canada thistle, field bindweed, and velvetleaf were largely unaffected. Monocots tested were largely immune.

Dinitroaniline herbicides have been used on the Texas Southern High Plains since the mid-1960s. Over this same period, cotton yields in this region have declined in spite of improved varieties and technology. Repeated applications of trifluralin and pendimethalin, each applied at 1x and 2x rates, were incorporated in 1983 through 1988. Variations in cotton stands, yields, and fiber quality were high due to environmental conditions. After six repeated applications, no reductions in cotton growth or yield were observed, even at the highest rates.

Research was conducted to compare cotton and tomato response to volatility of 2,4-D, dicamba, and triclopyr formulations. Herbicide treatments were applied to tilled soil during August and September, and potted plants were placed in the center of treated strips. To quantify injury, leaf cupping/crinkling/drooping; leaf rolling/strapping; stem epinasty; and stem swelling/cracking were each visually rated on an injury scale of 0 to 5 (0 = none, 1 = slight, 2 = slight to moderate, 3 = moderate, 4 = moderate to severe, and 5 = severe). Leaf cupping/crinkling/drooping injury averaged across herbicide treatments at 1× rates was 1.0 for cotton and 2.0 for tomato 14 d after treatment (DAT). Averaged across crops, leaf cupping/crinkling/drooping injury for the 1× rates 14 DAT was equivalent for the 2,4-D dimethylamine (DMA) salt, 2,4-D acid, dicamba DMA salt, dicamba diglycolamine (DGA) salt, dicamba acid, and triclopyr acid formulations and ranged from 1.1 to 1.8. For tomato, the only herbicide treatments with injury 14 DAT no greater than for the nontreated were 1× rates of 2,4-D DMA and 2,4-D acid for leaf rolling/strapping (1.0); 2,4-D acid, dicamba DMA, dicamba acid, and triclopyr acid for stem epinasty (0.3 to 0.7); and 2,4-D DMA, 2,4-D acid, dicamba DMA, dicamba DGA, dicamba acid, and triclopyr acid for stem swelling/cracking (0.1 to 0.2). A weighted factor assigned to each injury criterion provided an overall total injury estimate of 0 to 100%. When applied at 1× rates, total injury for 2,4-D isooctyl ester was 10% for cotton and 36% for tomato and for triclopyr butoxyethyl ester was 11% for cotton and 50% for tomato. For the 2,4-D DMA, 2,4-D acid, dicamba DMA, dicamba DGA, dicamba acid, and triclopyr acid formulations, total injury was 4 to 8% for cotton and 20 to 24% for tomato, and for both crops, injury was no greater than for the nontreated.