Dr. Michelle Moyer, Extension Viticulturalist located at Prosser, WA recently contacted me and told me that she was getting an uptick in calls from grape growers suffering 2,4-D damage in their vineyards. It has been a windy, cool spring, which may explain some of the drift issues, but wheat growers need to be aware of how sensitive grapes are to 2,4-D and other auxin imitator herbicides (Group 4). Preventing Herbicide Drift and Injury to Grapes (EM 8860) is a very good Extension publication from Oregon State University that discusses herbicide injury in grapes caused by herbicide drift and how to prevent herbicide drift to grapes.
Wheat growers should also be aware of state and county rules regarding the application of phenoxy herbicides. These rules for Eastern Washington can be found on the Washington State Department of Agriculture Eastern Washington – County Use Restricted Pesticide Rules website.When used properly, 2,4-D and other auxin imitator herbicides can provide effective and economical control of broadleaf weeds in wheat production systems. However, caution must be used to prevent off-target movement of these useful tools. This will not only help prevent injury to nearby crops, but will also increase the efficacy of the herbicides on their intended targets.
For questions or comments, contact Drew Lyon by email at drew.lyon@wsu.edu or by phone at 509-335-2961 or contact Dr. Michelle Moyer via email at michelle.moyer@wsu.edu.