Hi, my Concord grape vines are having some issues this season and I can not determine what the cause is. Last year I had to battle Japanese Beetles and then late in the season powdery mildew. I've never had problems this early in the growing season. I've included some images of what I am seeing. Thanks so much for your help.
The spots on your leaves are black rot. There is probably a diseased cluster (from last year with shrivelled berries) nearby that produced inoculum for the leaf spots you saw. Information at: http://nysipm.cornell.edu/factsheets/grapes/diseases/grape_br.pdf
Its the most common 'homeowner' problem. Commercial growers can control it with fungicide sprays timed at 1) Prebloom, 2) postbloom, 3) 2 wk later. I'd consult the Midwest Grape spray guide https://ag.purdue.edu/hla/Hort/Documents/ID-169.pdf for specifics. Ours is also available, but behind a pay wall.
The other issue is Tumid Gallmaker, a minute fly that lays its eggs in grape tissue, then the larvae form galls. There is one generation per year, so what you see now is what you have. We don't recommend insecticides for this pest, which will also not necessarily build up of left untreated.
Hope this answers your question.
Thank you so much for the help. There are actually a few shriveled up clusters from last year. I will look into the information you provided and will hopefully get the problem under control. Tumid gallmakers, that's a new one. For such a little pest they sure make a big mess. Thanks again !
Thanks! Tumid gall is sporadic, and in commercial terms, has little economic effect - although it is highly visible.