(343) Weed Controlin Vineyard Following Fall and Spring Application of Selected Herbicide Combinations

Abstract

Soil residual herbicides registered for use on grapes can be applied from fall to spring, before weed emergence. However, ample early-spring moisture and warm weather may enhance weed emergence before herbicide application in the spring and prevent timely application. Therefore, fall application of herbicides can be beneficial if herbicides would provide adequate weed control in the following spring. Warm and wet winters may enhance herbicide degradation and shorten herbicide residual activity that result in poor weed control the following spring. Fall and spring application of oryzalin or norflurazon applied alone or in combination with diuron, simazine, or oxyfluorfen were evaluated for weed control in commercial vineyards at Oskaloosa and Eudora in northeast Kansas in 2003 and 2004. Weeds were not controlled adequately with oryzalin or norflurazon applied alone. At the end of the growing season, however, weed control was greater with spring than fall application. In addition, weed control with norflurazon was slightly greater than oryzalin. Norflurazon or oryzalin applied in combination with simazine, diuron, or oxyfluorfen controlled more weeds than norflurazon or oryzalin applied alone. The greatest control was with norflurazon or oryzalin applied with oxyfluorfen. In general, all herbicide combinations applied in the spring and fall provided similar weed control 4 months after spring application. However, at the end of the growing season, weed control was 10% to 20% greater when herbicides applied in the spring than fall. This study showed that acceptable weed control can be achieved when norflurazon or oryzalin is applied with oxyfluorfen and diuron in the fall.