BROADLEAF WEED-CONTROL IN POTATOES (SOLANUM-TUBEROSUM) WITH POSTEMERGENCE DIRECTED HERBICIDES

Field studies were conducted to evaluate potato injury and weed contro l with postemergence-directed (PDIR) bromoxynil, glufosinate, or monoc arbamide dihydrogen sulfate (MCDS). All three herbicides controlled ha iry nightshade, common lambsquarters, redroot pigweed, and kochia grea ter-than-or-equal-to 85%, depending on rate, with either mid- or late- PDIR treatment. Bromoxynil or MCDS caused 5 to 6% more initial injury with mid- than with late-PDIR treatment, but total yield and yield of U.S. #1 tubers were not reduced by either herbicide. PDIR glufosinate caused moderate injury at 0.84 kg ha-1, the rate needed for acceptable (> 85%) weed control. Total yield was reduced 10% and U.S. #1 yield w as reduced 30% by PDIR glufosinate at 0.84 kg ha-1. Thus bromoxynil an d MCDS showed potential for use as PDIR treatments in potatoes, but gl ufosinate did not.