Published online by Cambridge University Press: 20 January 2017
Field studies were conducted to assess weed control and potato (Solanum tuberosum) tolerance to ethalfluralin. Ethalfluralin applied preemergence (PRE) alone at 1.05 kg ai/ha generally did not control weeds adequately. However, ethalfluralin at 1.05 kg/ha combined with either metribuzin at 0.28 kg ai/ha or rimsulfuron at 0.018 kg ai/ha controlled common lambsquarters (Chenopodium album), redroot pigweed (Amaranthus retroflexus), and green foxtail (Setaria viridis) ≥ 98%, which was similar to control observed with several currently registered herbicide mixtures. Volunteer oat (Avena sativa) control with either ethalfluralin at 1.05 kg/ha plus EPTC 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 either rimsulfuron or EPTC controlled hairy nightshade equal to or better than the registered two-way mixtures evaluated. A sequential application of ethalfluralin PRE followed by rimsulfuron or rimsulfuron plus metribuzin postemergence (POST) did not improve hairy nightshade control compared to ethalfluralin plus rimsulfuron applied PRE. Potato tolerance to herbicide treatments applied PRE or POST to potato was evaluated in weed-free studies. Ethalfluralin alone or with metribuzin was compared to mixtures of metribuzin with either pendimethalin or EPTC. Initial visual injury with ethalfluralin PRE was ≤ 4% both years. In 1996, initial injury with ethalfluralin POST was ≤ 4% and U.S. No. 1 and total tuber yields were not affected by herbicide treatment or application timing. However in 1997, initial injury from POST ethalfluralin 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.