POSTEMERGENCE WEED-CONTROL IN POTATOES (SOLANUM-TUBEROSUM) WITH RIMSULFURON

Greenhouse and field studies were conducted to examine weed control with, and potato tolerance to, rimsulfuron or rimsulfuron + metribuzin applied POST. In greenhouse trials, hairy nightshade control with rimsulfuron applied POST at 9 to 35 g/ha was greater-than-or-equal-to 90%, but cutleaf nightshade control was < 30%. In field studies, rimsulfuron at 18 to 35 g/ha provided greater-than-or-equal-to 85% control of hairy nightshade, redroot pigweed, tumble pigweed, and shepherd's-purse; 75 to 82% control of volunteer oats; and 25 to 87% control of common lambsquarters. Common lambsquarters control was increased to 92 to 100% when rimsulfuron at 18 to 35 g/ha was applied in combination with metribuzin at 280 g/ha. Hairy nightshade and redroot pigweed control usually were not improved by adding metribuzin to the rimsulfuron spray mixture and tumble pigweed and shepherd's-purse control were improved only slightly. Volunteer oat control with rimsulfuron sometimes was antagonized by the addition of metribuzin to the spray mixture. In weed-free trials, yield of potatoes grown for the fresh market or to produce seed tubers was not reduced by rimsulfuron at rates as high as 70 g/ha. Nomenclature: Metribuzin, 4-amino-6-(1,1-dimethylethyl)-3-(methythio)-1,2,4-triazin-5(4H)-one; rimsulfuron, N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-(ethylsulfonyl)-2-pyridinesulfonamide; hairy nightshade, Solanum sarrachoides Sendtner #3 SOLSA; cutleaf nightshade, Solanum triflorum Nutt. # SOLTR; common lambsquarters, Chenopodium album L. # CHEAL; redroot pigweed, Amaranthus retroflexus L. # AMARE; tumble pigweed, Amaranthus albus L. # AMAAL; shepherd's-purse, Capsella bursa-pastoris (L.) Medicus # CAPBP; volunteer oat, Avena sativa L.; potato, Solanum tuberosum L. 'Russet Burbank.'