Author(s)

Seshadri S. Reddy, Phillip W. Stahlman, Patrick W. Geier

Agricultural Research Center, Kansas State University, Hays, KS, USA.

A field study was conducted at two locations in Kansas, USA in 2011 and 2012 to test weed control efficacy and crop response to preemergence-applied pyroxasulfone alone and in combination with sulfentrazone in sunflower. Treatments included three rates of pyroxasulfone (100, 200 and 400 g·ha^-1) applied alone and tank-mixed with sulfentrazone at 70, 140 and 280 g·ha^-1. Commercial standards sulfentrazone at 140 g·ha^-1 + pendimethalin at 1390 g·ha^-1 and sulfentrazone at 140 g·ha^-1 + S-metolachlor at 1280 g·ha^-1 were also included. Pyroxasulfone at 100 g·ha^-1 controlled Palmer amaranth 87% at 3 weeks after application (WAA), but control decreased to 76% at 6 WAA. Increasing pyroxasulfone rate to ≥200 g·ha^-1 or tank mixing with sulfentazone at 140 g·ha^-1 provided ≥90% Palmer amaranth control for at least 6 WAA. Sulfentrazone alone at 70 g·ha^-1 controlled Palmer amaranth 77% at 3 WAA, but control dropped to 69% at 6 WAA. Increasing sulfentrazone rate from 70 to 140 or 280 g·ha^-1 increased control to >90% at 3 WAA, but did not maintain acceptable control at 6 WAA. Tank mixing sulfentrazone at 140 g·ha^-1 with pendimethalin at 1390 g·ha^-1 or S-metolachlor at 1280 g·ha^-1 controlled Palmer amaranth ≥90 and 84% at 3 WAA and 6 WAA, respectively. The lowest rate of pyroxasulfone (100 g·ha^-1) controlled kochia 98% and the control was complete with all other treatments. However, no treatment provided as much as 90% puncturevine control at 3 WAA and the control was commercially unacceptable (<75%) at 6 WAA. No treatment visibly injured sunflower anytime during the season or reduced sunflower plant population.

Pyroxasulfone, Sulfentrazone, Sunflower, Weed Control, Palmer Amaranth, Kochia

S. Reddy, S. , Stahlman, P. and Geier, P. (2015) Broadleaf Weed Control in Sunflower (Helianthus annuus) with Preemergence-Applied Pyroxasulfone with and without Sulfentrazone. Agricultural Sciences, 6, 1309-1316. doi: 10.4236/as.2015.611125.