Combinations of Penoxsulam and Diquat as Foliar Applications for Control of Waterhyacinth and Common Salvinia: Evidence of Herbicide Antagonism

摘要

Waterhyacinth (Eichhornia crassipes [Mart.] Solms) and common salvinia (Salvinia minima Baker) are two' floating aquatic plants that can cause wide-spread problems in the southern United States. These species can cause reductions in ecosystem functionas well as the abundance of native plant species. Herbicides are often used in an attempt to control both species; however, few recommendations exist for common salvinia. Penoxsulam (2-(2,2-difluoroethoxy)-N-(5,8 dimethoxy [1,2,4] triazolo [1,5-c] pyrimidin-2-yl)-6 (trifluoromethyl) benzenesulfonamide) is newly registered for use in aquatic environments and is efficacious on floating plants as a submersed application; however, foliar application rates are largely undefined. The objectives of these studies were to determine the effect of foliar application rates of penoxsulam for waterhyacinth and common salvinia, and to evaluate the effectiveness of combinations of penoxsulam with diquat against these same plants species. A mesocosm study was conducted using foliar rates of penoxsulam (24.5, 49.1, and 98.2 g ai ha~(-1)) alone and in combination with diquat (130.8 g ai ha~(-1)). At six weeks after treatment (WAT), penoxsulam alone at all rates resulted in 100% control of waterhyacinth, and at 10 WAT control remained >90%. Penoxsulam was not as effective at controlling common salvinia. The combination of herbicides did not increase efficacy, and there was evidence of antagonism at the rates tested. Future studies should assess lower rates for waterhyacinth control and influences of salvinia mat thickness on application timing and herbicide efficacy.