Question: I have been growing grapes for seven years. Last year and this year, I have had problems with the leaves. I have attached two photos. Can you please tell me what is wrong with my vines? They are still producing grapes.
I think I am seeing two things. One is some strong discoloration between the veins, almost white. The other is some black speckles all over the leaves.
If I am seeing this correctly, I think you have some leafhopper damage (black speckles). Leafhoppers are tiny bugs that jump all over the place when you are handling the leaves or even walking by the vines. I think the white discoloration between the leaf veins is an iron problem.
With the jumping bugs, you could have sprayed Spinosad in May when they were young, and you could have knocked the population back. That would have been the same time for controlling skeletonizers and hornworms, so you would have hit three pests with two applications about one week apart.
The other would be controlled with an iron chelate application to the base of the grape plant in about March, just before new growth. It would be watered in after you applied it. The iron chelate to use would be EDDHA.
Bob Morris is a professor emeritus in horticulture with the University of Nevada and can be reached at firstname.lastname@example.org. Visit his blog at xtremehorticulture.blogspot.com. For more, see the Thursday edition of the Las Vegas Review-Journal.