California Grapes: Managing Weeds in Drought Conditions
Drought conditions in grapes create unique challenges to weed control. Without rain there is little competition from annual weeds, so you may see more deep-rooted perennial weeds that are harder to control, especially field bindweed (Convolvulus arvensis).
Preemergence herbicides require approximately 1/4 to 1/2 inch of water within 3 weeks after application. If you decide to use a preemergence herbicide, you’ll need to wait for when rain is predicted or sprinkler irrigate.
If weeds are a problem now you can apply a contact herbicide. Postemergence systemic herbicides are effective too, but some weeds are resistant or tolerant; if you choose to use one, first learn about herbicide resistance.
Areas treated only with a postemergence herbicide may need light cultivation to remove weeds usually controlled with a preemergence herbicide.
For more information on preemergence and postemergence herbicides, weed susceptibility, and weed management visit the Grape Pest Management Guidelines. View the grape year-round IPM program for more information on pest monitoring and management during winter.