ABSTRACT

A field study was established at Maricopa, AZ to compare reduced rates of trifluralin (TREFLAN* 5) to pendimethalin (PROWL** 4). Two rates of each herbicide were compared; 0.5 and 0.75 lb ai/ac trifluralin and 0.75 and 1.0 lb ai/ac pendinethalin. The herbicides were applied flat and incorporated 3-in deep with an S-tine harrow prior to listing. The soil was a sandy clay loam (0.8% O.M.). Efficacy was measured 30-, 45-, and 60-d after application and cotton stand was measured 30-d after application. Sweetpotato whitefly densities were extremely high during the course of the study. Neither herbicide provided >75% control of Wright groundcherry (Physalis spp.). All herbicide treatments resulted in seed cotton yields that were significantly higher than the weedy control plots. Stand counts, seed cotton yields, and efficacy on seedling johnsongrass (Sorghum halepense) and Palmer amaranth (Amaranthus Palmeri) suggest that trifluralin at 0.5 lb ai/ac is similar to pendimethalin at 0.75 lb ai/ac.