Soil-residual herbicides can be applied to the soil under grapevines during fall or spring before weed emergence. But, early spring moisture and warm weather conditions may enhance weed emergence before spring herbicide applications. Therefore, fall application of herbicide can be useful if the herbicides provide adequate weed control the following spring and summer. Fall and spring applications of oryzalin or norflurazon, applied alone or in combination with diuron, simazine, or oxyfluorfen, were evaluated for weed control in grape at Oskaloosa and Eudora in northeast Kansas in the 2002 to 2003 and 2003 to 2004 growing seasons. Weeds were not controlled adequately with oryzalin or norflurazon applied alone. At the end of the growing season, weed control was 10 to 20% greater when herbicides were applied in the spring than when applied in the fall. In addition, weed control with norflurazon was slightly greater than with oryzalin. In general, norflurazon or oryzalin applied in combination with simazine, diuron, or oxyfluorfen gave greater weed control than norflurazon or oryzalin applied alone. The greatest control was with norflurazon or oryzalin applied with oxyfluorfen. In general, all herbicide combinations provided similar weed control 4 mo after spring treatment in 2003 and 3 mo after spring treatment in 2004. This study showed that acceptable weed control can be achieved when norflurazon or oryzalin is applied with oxyfluorfen or diuron in the fall.
Nomenclature: Diuron; norflurazon; oryzalin; oxyfluorfen; simazine; grape, Vitis labrusca #3 VITLA.
Additional index words: Grape injury, common ragweed, horseweed, prickly sida, prickly lettuce, tumble windmillgrass, yellow sweetclover.
Abbreviations: MAST, month after spring treatment.
