I have NEVER had so much loss from coulure as I have this year. I grow 12 bearing vines this year and all but 2 of them had there clusters wiped by coulure. Was it just me or did anyone else have an exacerbated episode of this?
I kinda think it might be time to fertilize, which I haven't done in the 8 years I've had vines, but there are no signs of P deficiency or excess N for that matter since those issues can cause coulure. I highly doubt it was disease either. I was actually on the ball with it this year and started spray at budbreak but there was some anthracnose. I'll post some pics. I have heard that excessive warmth can cause it. If there's no other cause, I'd bet on the warmth.
EDIT- After writing that, I recalled that I got hit early with herbicide damage. Everything that showed foliar signs of damage lost their clusters. I wonder if the herbicide directly or indirectly caused this. It was a strange thing too. 2,4d and dicamba (by far the most popular herbicides here in IN) only affect certain vines and there were vines damaged that don't get affected by either. Very curious.
I'd have to agree. It warms up early here and then gets followed by a cool May. I decided to try some late pruning to see if I could get a useable harvest off from secondary buds but I only tried it on Marquette. Pressing the reset button this late is risky.