Abstract
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.
Highlights
In the United States, sunflower (Helianthus annuus L.) is cultivated in the Great Plains Region for cooking oil, confectionary uses, and birdseed
Multiple coordinated field experiments from North Dakota to Kansas over a three-year period indicated preemergence (PRE)-applied pyroxasulfone controlled many annual grass and broadleaf weeds as well or better at rates three to eight-times lower than herbicides currently registered for use in sunflower with only occasional incidences of minor injury that did not reduce seed yield [14]
In 2012, mm rainfall was received over a period of 4 days after herbicide application (DAA) at Hays and mm irrigation water was applied through overhead sprinkler system over a period of 5 DAA at Colby
Summary
In the United States, sunflower (Helianthus annuus L.) is cultivated in the Great Plains Region for cooking oil, confectionary uses, and birdseed. Multiple coordinated field experiments from North Dakota to Kansas over a three-year period indicated preemergence (PRE)-applied pyroxasulfone controlled many annual grass and broadleaf weeds as well or better at rates three to eight-times lower than herbicides currently registered for use in sunflower with only occasional incidences of minor injury that did not reduce seed yield [14]. In two of those experiments, pyroxasulone at 208 g∙ha−1 controlled Palmer amaranth 87 - 97% and a tank mixture of 167 g∙ha−1 pyroxasulfone plus 105 g∙ha−1 sulfentrazone provided complete Palmer amaranth control [15]. A study was conducted to evaluate weed control efficacy and sunflower response to different rates of pyroxasulfone with and without sulfentrazone
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