Last year some disease or condition came upon my grapes; this year it has taken over. Last year BMSB (Brown Marmorated Stink Bugs) showed up en masse, like nothing I had seen before. These are possibly related…I don’t know. I can’t find any good photos of Pierce’s Disease in progress, and it’s the only thing that shows up in a search that looks anything like what is on these grapes. Any ideas?
General Condition Before Total Wilt
Seedy, I couldn’t tell from the pics, but the discoloration on the tips/young leaves, is that reddish or brown? If red-purple, it might be due to a phosphorus deficiency, which can be due to colder soil temps and/or an actual deficiency in the soil.
If it is a phosphorus deficit, then a foliar spray with an appropriate P fert for that purpose would help (however if it is a fungus/bacteria a fertilizing spray may well make it worse).
Continuing to search I think it looks more like frost damage than anything else. I think we might have had a freezing night a couple weeks ago. I remember seeing this (I think it was the same thing) last year…I guess it was in the Fall. To me, it doesn’t look like a Phosphorus problem. I’ll remember that though, and just continue to watch.
Not P nor freeze damage. Looks more like a fungus problem. I’ve never had Downy mildew but maybe that or another fungus.
Thanks for the ideas! Nothing that I look up (Google) looks like this. Frost injury is the closest, and yet there are things that don’t add up about it, too. Fungus makes more sense. I am minutes away from Oregon St. Univ. and they are good with Ag and there should be grape pros on site. When I figure out who to send these photos to I’ll get on it. Thanks for the pointers.
I’m pretty sure it was frost injury. It has faded away now.