Virginia Grape Disease Updates

It finally stopped raining, but we (Winchester area) are having an on-going wet event since 10/9/13.  I counted >108 hours of wetness with an average temperature of 54F (ranging from 48F to 60F).  It has been a long enough for Botrytis, and although the temperature was bit low, downy mildew probably had some chances as well. Here is a list of things to be considered: 1) Time to harvest (if you are picking in a few days, I do not see the benefit of spraying now) 2) Current Botrytis situation in your vineyards 3) Variety (red with loose cluster ~ lower Botrytis risk) 4) Canopy management (Open fruiting zone is always helpful!) 5) Birds/insect damages (more damages, higher the Botrytis risk) 6) Fungicide effect on wine quality As I mentioned earlier this week, we had Botrytis risk event on last Monday; however, it had been dry for several weeks until that rain.  Thus, the Monday's risk might not have resulted in many infections.  On the other hand, Botrytis spores are ve

Rain on this Monday resulted in 10 hours of wetness with an average temperature of 62F.  It was warm and long enough for both downy mildew and Botrytis.  Once again, downy mildew risk is for leaves only.  Risk of Botrytis depends on your variety, cluster architecture, and canopy management too.  Most of varieties still hanging are red (with some exceptions, of course), which has lower risk of Botrytis.  Also, if you have an open canopy, the risk are lower too.