Preemergence weed control in potato (Solanum tuberosum) with ethalfluralin

Field studies were conducted to assess weed control and potato (Solanum tub erosum) tolerance to ethalfluralin. Ethalfluralin applied preemergence (PRE ) alone at 1.05 kg ai/ha generally did not control weeds adequately. Howeve r, ethalfluralin at 1.05 kg/ha combined with either metribuzin at 0.28 kg a i/ha or rimsulfuron at 0.018 kg ai/ha controlled common lambsquarters (Chen opodium album), redroot pigweed (Amaranthus retroflexus), and green foxtail (Setaria viridis) greater than or equal to 98%, which was similar to contr ol observed with several currently registered herbicide mixtures. Volunteer oat (Avena sativa) control with either ethalfluralin at 1.05 kg/ha plus EP TC at 3.4 kg ai/ha or ethalfluralin plus metribuzin was equal to registered two-way mixtures. Ethalfluralin plus metribuzin did not adequately control hairy nightshade (Solanum sarrachoides), but ethalfluralin mixtures with e ither rimsulfuron or EPTC controlled hairy nightshade equal to or better th an the registered two-way mixtures evaluated. A sequential application of e thalfluralin PRE followed by rimsulfuron or rimsulfuron plus metribuzin pos temergence (POST) did not improve hairy nightshade control compared to etha lfluralin plus rimsulfuron applied PRE. Potato tolerance to herbicide treat ments applied PRE or POST to potato was evaluated in weed-free studies. Eth alfluralin alone or with metribuzin was compared to mixtures of metribuzin with either pendimethalin or EPTC. Initial visual injury with ethalfluralin PRE was less than or equal to 4% both years. In 1996, initial injury with ethalfluralin POST was less than or equal to 4% and U.S. No. 1 and total tu ber yields were not affected by herbicide treatment or application timing. However in 1997, initial injury from POST ethalfuralin at 1.05 or 2.1 kg/ha was 2 or 8% and increased to 9 or 17%, respectively, at potato row closure . Averaged over all herbicide treatments, POST applications reduced U.S. No . 1 and total tuber yield 7% relative to PRE applications in 1997.