grape vine disease

Asked July 3, 2014, 3:18 PM EDT

Our grapes have some sort of disease. The berries are turning black and some leaves are spotted. Is this black rot or some other problem and how can we stop the grapes from dying?

Wayne County Michigan grapes

1 Response

Yes, it sounds like black rot, which is manifesting itself now due to the rainy weather that we have had. Most of these infections took place several weeks ago and infected berries cannot be saved. The vines will be fine but you will lose some of the fruit and a few leaves prematurely. You may still be able to spray a fungicide to stop more berries from getting infected. Any registered fungicide that has myclobutanil or tebuconazole in it will be the most effective. Your best bet is to prepare for next year by removing all rotted fruit and burning or burying them; in winter, prune out infected canes and any remaining fruit clusters; in the early spring, you can apply copper sulfate or lime sulfur to the dormant vine to kill the overwintering fungus, and next summer, apply one or two sprays of an effective fungicide immediately after bloom and 2 weeks later to protect the fruit from infection. Let me know if you have more questions, Best wishes,