Effectiveness of Herbicides for Control of Hairy Vetch (Vicia villosa) in Winter Wheat

A field experiment was conducted in 2009-2010 at Pennsylvania and Maryland locations, and repeated it in 2010-2011 to test the effectiveness of POST-applied herbicides at fall and spring timings on seeded hairy vetch in winter wheat. A total of 16 herbicide treatment combinations was tested that included synthetic auxins, acetolactate synthase (ALS) inhibitors, and a protoporphyrinogen oxidase inhibitor. Spring applications tended to be more effective than fall applications. Among synthetic auxins, clopyralid (105 g ae ha(-1)) and treatments containing dicamba (140 g ae ha(-1)) were effective at both timings, resulting in greater than 90% hairy vetch control at wheat harvest. Pyroxsulam and prosulfuron applied at 18 g ai ha(-1) provided the most effective hairy vetch control (> 90%) at both application timings among ALS inhibitors. Spring applications of several herbicides provided moderate (> 80%) to high (> 90%) levels of hairy vetch control, including: 2,4-D amine (140 g ae ha(-1)), mesosulfuron-methyl (15 g ai ha(-1)), tribenuron-methyl (13 g ai ha(-1)), and thifensulfuron/tribenuron-methyl treatments (16 and 32 g ai ha(-1)). Winter wheat injury was evaluated, but symptoms were negligible for most treatments. Winter wheat yields declined with increasing hairy vetch biomass. Fall herbicides may be prioritized to reduce hairy vetch competition during the fall and early spring growing season. Our research has established that several synthetic auxin and ALS-inhibiting herbicides, applied POST in fall or spring, can be safely used in winter wheat to control hairy vetch in an integrated weed management program.