WINE GRAPE (VITIS-VINIFERA) RESPONSE TO REPEATED EXPOSURE OF SELECTEDSULFONYLUREA HERBICIDES AND 2,4-D

'Lemberger' wine grape response was evaluated when chlorsulfuron, trib enuron, thifensulfuron, chlorsulfuron plus metsulfuron, thifensulfuron plus tribenuron, and 2,4-D were applied up to three times at weekly i ntervals in 1992 and 1993 at rates simulating drift. All herbicides in jured grapevines visibly. Symptoms increased and total leaf area and g rape pruning weight decreased as the herbicide rate and number of appl ications increased. Grapevines generally recovered within 45 to 60 d f rom symptoms caused by single exposures to low levels of sulfonylurea herbicides. Multiple exposures of grapevines to 2,4-D, tribenuron, and chlorsulfuron plus metsulfuron at 1/100 of the maximum use rate for w heat caused the greatest injury, which persisted throughout the entire growing season and reduced pruning weight, Based on potential use rat e, the order of herbicide phytotoxicity was 2,4-D > tribenuron > chlor sulfuron plus metsulfuron > thifensulfuron plus tribenuron > chlorsulf uron > thifensulfuron. Rates that slightly injured grapevines did not reduce growth as measured by pruning weight. However, multiple exposur e to high rates of 2,4-D, tribenuron, and chlorsulfuron plus metsulfur on adversely affected growth.