Virginia Grape Disease Updates

With this week's precipitations that we (including many meteorologists) did not anticipated last week, some of you have contacted me to seek options for the late season application, especially for red-fruited cultivars that need to stay on the vine for a few more weeks.  Here's a table for late season fungicide options, with materials that has 7 or fewer PHI (it will open Google Drive's spread sheet).   The efficacy information is based on our PMG, which can be downloaded from the right hand side of the blog.  (It says 2014, but the file is updated to 2015).  Hopefully we will see the sun soon! Good luck with the rest of the season.  It's almost done!!!

I have heard from several growers that they are seeing downy mildew despite the fact that they have not seen much precipitations.  It could happen because of the humidity, especially during the night.  Warm, humid, and dark condition (just like we have been having during the last few weeks) promotes downy mildew pathogen to produce spores. In addition to these conditions, we had lines of rain storms passed in our areas in the past two days. The length of wetness due to these storms were probably long enough for downy mildew pathogen to cause infection. So, just a reminder.  If you have seen downy mildew, and you have not applied any protective material (captan, Revus, even phosphorous acid products) in the past 10 days or so, you may want to consider a rescue application of a phosphorous acid product to reduce the risk of infection that might have happened in the past two days of rains.  (Note: If you are considering harvest in a few days, I would wait until harvest.) If you have

Dr. Wayne Wilcox at Cornell University wrote an article on sour rot management on " Finger Lakes Vineyard Notes ". (The link will open a pdf file)  Please check it out.  Results from his research group is showing that 1) good canopy management matters, and 2) management of insect (fruit flies) seems to have a big impact on the development of sour rot.  Since their regions do not have issues with spotted wing Drosophila (aka SWD), even regular fruit flies, which cannot damage grape skin, can still aid transmission of sour rot pathogens.  I know some of us in VA have been managing SDW in the past few years. If you have managed SWD and have seen lower level of sour rot, please let me know.