ABSTRACT

Cotton producers on the Texas High Plains face increasing problems with broadleaf annual weeds that are not effectively controlled with current preplant incorporated or preemergence herbicides. Field experiments were conducted in 1991 and 1992 at the Texas Agricultural Experiment Station near Lubbock to evaluate DPX-PE350 (Staple) for weed control in cotton. Preplant incorporated (PPI), preemergence (FE), and postemergence topical (PT) applications were made at rates ranging from .032 to .125 lb ai/acre. All herbicide treatments were applied using a tractor-mounted compressed air plot sprayer and crop oil concentrate was added to all PT applications. Weed species evaluated in these experiments included palmer amaranth (Amaranthus Palmeri S. Wats.) devils claw [Proboscidea louisianica (Mill.) Thell.] lanceleaf sage (Salvia rethexa Hornem.), and barnyardgrass Echinochloa crus-galli (L.) Beauv.).

PPI applications of DPX-PE350 controlled palmer amaranth at .032 lb/A. Devilsclaw was controlled at .063 lb/A. DPX-PE350 did not control barnyard grass effectively at even the highest rates evaluated. A PPI combination of trifluralin (0.6 lb ai/A) + DPX- PE350 (.063 lb/A) effectively controlled all three species throughout the growing season.

PE applications at .063 lb/A controlled palmer amaranth and lanceleaf sage. Devilsclaw control with PE treatments was not as effective as with PPI applications. PE barnyardgrass control was poor.

PT applications of DPX-PE350 applied to small weeds (1-2 inches tall) controlled palmer amaranth and lanceleaf sage. Higher rates (.063-.125 lb/A) were required for control of devilsclaw and larger palmer amaranth. DPX-PE350 offers potential for both preemergence and postemergence control of several problem weeds in cotton on the Texas Southern High Plains that are not effectively controlled with current herbicides. The most appropriate application timing will depend upon crop selectivity, costa, and specific weed problems.