SPLIT AND TANK-MIX PREEMERGENCE APPLICATION OF HERBICIDE FOR CONTROLLING WEEDS IN GRAPES

Spring vs. fall plus spring (split) herbicide application times and si ngle vs. tank-mix spring herbicide applications were compared as a mea ns of extending summer annual weed control in vineyards. About 30% of the nontreated control areas were weed-covered by April or May of each of 3 years. Most treatments gave 60 or more days of acceptable annual weed control (less-than-or-equal-to 30% cover) beyond the nontreated control. Fall plus spring application of diuron, norflurazon, or simaz ine at the half-label rate did not increase the days of control over s pring application alone at the full-label rate. The tank-mixed herbici des diuron, norflurazon, and oryzalin in combinations of any two at th e half-label rate were as effective as the full-label rate of these he rbicides used alone. Weed control by oxyflurofen or simazine was exten ded by tank-mixing with oryzalin (half-label rates). Chemical names us ed: N-(3,4-dichlorophenyl)-NN-dimethylurea (diuron); no)-2-(a,a,a-trif luoro-m-tolyl)-3(2H)-pyridazinone (norflurazon); 3,5-dinitro-N4,N4-dip ropyl-sulfanilamide (oryzalin); ro-l-(3-ethoxy-4-nitrophenoxy)-4-(trif luoromethyl) benzene (oxyfluorfen); and 2-chloro-4,6-bis(ethylamino)-s -triazine (simazine).