Virginia Grape Disease Updates

It has been pretty wet week so far. At Winchester, we observed about 11 hours of wetness on the 26th with an average temperature of 64F, 50+ hours (and counting) from the 28th to today with an average temperature of 61F. It is certainly long and warm enough for Botrytis infection. Whether we require a fungicide application for Botrytis or not at this point depends on several potential factors. The first one, of course, is whether you had a previous application or not. If you had a previous application to cover these rain events, you probably do not need to be concerned much. The second one is a time to harvest. If you still have several weeks to go, you may want to consider an application, but if you will harvest within a few days, I am not sure an application of fungicide will help you much since we do not have any curative materials for Botrytis. Whatever we spray at this point will be good against future infections, but not the infection happened already. The third is cultivar...

Maybe I should keep posting that rains are coming... Each time I do, it looks like rains disappear. ;) If you have not subscribed to the email list of Dr. Tony Wolf, who is our viticulturist, please do. It always have a wealth of information. In his latest newsletter, he explores potential reasons why some of cultivars are stalling on ripening process this year. Our Chardonnay is still stuck at 19 Brix or so too! The below is a link to his newsletter, but it typically take several days for the newest one to appear. Thus, the best way is to subscribe to his email list (the instruction for subscription is listed on the page too). http://www.arec.vaes.vt.edu/alson-h-smith/grapes/viticulture/extension/VN_options_index.html

Well, I was hoping that the rest of the season would be nice and sunny, but I was little naive. Looks like some portion of VA may be affected by tropical storm Hermine. Plus, probably due to the hot several weeks with no cooling time during the night in August, some cultivars have been very slow to ripen. I was bit surprised to see our Chardonnay is still around 17 Brix this week. Thus, I complied a list of fungicides with relatively low PHI (7 days or less). I cannot cover every single fungicides out there, but I tried to cover common ones. Please click here to download the table from Google drive. NOAA's precipitation prediction for Harmine as of 2 Sept. 2016