Some Defects on Grape Leaves May Be Normal

Q. Can you tell me what is wrong with the leaves on my Thompson seedless grape vine (see attached picture)?  Are there grape leaf miners?  What is the best pesticide to use to control these pests?

Readers grape leaf looks pretty healthy

A. I really did not see too much to be concerned about on the top of the leaf. Make sure you look at the bottom of the leaf, not just the top. Some insect pests will invade the leaves from the bottom. The leaves look pretty normal to me and I do not know of any leaf miners and grapes.

            However you are getting into the season where you will get grape leaf skeletonizer starting in May. Keep inspecting your leaves and around the next week or two begin spraying your grape leaves with Bt, an organic pesticide.

            Do this twice about 10 days apart in May. This should eliminate grape leaf skeletonizer as well as hornworm attacks. If these little bugs called leaf hoppers that jump when you walk past your grapevine are problem in the summer months then you might also apply to applications of spinosad around the same time as the BT.

            Do not mix them in the same sprayer because I am not sure they are compatible together in the same sprayer. Make sure you spray the top of the leaves as well as the bottom of the leaves. This is very important to get good coverage. Good luck.