Virginia Grape Disease Updates

Our Chardonnay clusters are getting larger and berries are starting to touch each other. It feels a bit early, but here are grape disease management reminders at berry touch/cluster closure stage. Botrytis gray mold: The best management practice is canopy management. Botrytis pathogen likes high humidity, thus, the poorly managed canopy that traps humidity will help them to thrive. This pathogen also needs wounds to develop spores, thus, grape berry moth and other insects plus birds need to be managed too. There is a number of Botrytis materials such as Rovral and Meteor (FRAC 2), Elevate (FRAC 17), Vanguard and Scala (FRAC 9), Luna Experience (FRAC 7 plus 3), Kenja (FRAC 7), Miravis Prime (FRAC 7 plus 12), Switch (FRAC 9 plus 12), etc. Botrytis pathogen is well known for its ability to develop fungicide resistance, so, please rotate FRAC codes!! QoI fungicides (FRAC 11) are no longer the effective material for us due to the development of QoI-resistant Botrytis isolates thro

My colleagues and I are seeking information on sour rot so that we can develop research priorities (and hopefully obtain grants). Many of us suffer from sour rot (remember the last season?), and we need to get our heads together. If you could fill in this short survey, we really appreciate. It should not take more than a few minutes to complete. It is not just for Virginia, so, please feel free to complete the survey if you grow grapes outside of Virginia. Sour rot survey (will open a new window) Thank you!!

Of course, once I mentioned the lack of rainfall, we  (i.e., northern VA)   were hit by a series of rain. To make things more complicated, we had at least three consecutive nights of warm and humid (RH > 90%) condition prior to the rains. Humid nights encourage downy mildew pathogen to produce spores, and rains will splash spores to healthy tissues. Thus, the risk of downy mildew during recent rain events was very high. ( Note : Central VA also had two humid nights in 7/5-7/6 at the Charlottesville airport, but the chance of rain is not high until this Thursday.) There are a number of materials can be used for protection: captan (FRAC = M4), mancozeb, ziram (FRAC = M3), Revus, Forum (FRAC = 40), Zampro (FRAC = 40 plus 45), Ranman (FRAC = 21)). Mancozeb products have the 66-day PHI, but ziram's PHI is 21 days.  Another good option is a copper (FRAC = M1) material, which is more economical than other materials. Copper has good efficacy against downy mildew, and tends to do w

It depends on where you are, but in northern VA, we are having relatively "dry" weather this summer. We have some rain events here and there, but overall, the air is humid, but not wet. Such a condition promote powdery mildew development, so, I just want to provide a reminder on powdery mildew management. (Powdery mildew symptom on a cluster: the picture was taken this morning) Powdery mildew pathogen thrives under shaded condition  (i.e., overcrowded canopy). Thus, canopy management is a very important aspect of powdery mildew management. Chemical management options: Sulfur (FRAC = M2) is an economical option. Copper (FRAC M1) works too, but compared with sulfur, copper seems to be slightly less effective. Other options are: DMI fungicides (e.g., Rally, Elite, Mettle, Rhyme, etc, FRAC 3), Quintec (FRAC 13), Vivando (FRAC 50), Luna Experience (FRAC 7 plus 3), Topguard EQ (FRAC 11 plus 3), Rhyme, Kenja, and Aprovia (FRAC 7), Torino (FRAC U6), etc. Please make sure to