Virginia Grape Disease Updates

I recently published a book chapter with my colleague about how to optimize fungicide application .  It is free to download, so, if you are looking for some bed time reading material, it may help you sleep.  ;)  The title sounds like we are developing a practical application guide for fungicide, and that was our intention at the beginning, but we did not have a space in the chapter (and time) to explore that.   Instead, we showed several examples of how research projects can be used to help optimize fungicide application.  Hopefully we will have another opportunity soon to actually work on more practical chapter.

Thank you for those of you who attended a beginner's workshop yesterday.  It was a very good opportunity for me to talk to you.  If you are interested in, we will hold another half-day beginner's workshop at next year's VVA annual meeting which will be held at Charlottesville in February. Here's the copy of the handout from yesterday.  Please click this sentence to download it.   It is in Adobe PDF format. I remember that  I mentioned that I will post something about ripe rot; however, I have been busy.  I will do my best to post the article in a few weeks!

I just saw Tony sent an email this afternoon to discuss about the sanitation issues.  I want to add a few more comments here to discuss this important issue.  (by the way, if you would like to be listed to Tony's email list which he also uses to publish his quarterly publication "Viticulture Note", please let me or Tony know) Since we finished the season with long rainy periods, some of you experienced increased level of downy mildew and/or Botrytis.  In addition, I have seen several outbreaks of ripe rot (which I will discuss in the next posting), and other general rots (sour rot, Aspergillus, Penicillium, etc.).  Because of that, we probably have a higher risk of having these diseases in the next season.  The question is how to deal with them. As Tony noted, it is probably a good idea to move them from the vines and place them in the middle of the row, then remove or mow.  If the berries are hanged in the trellis, these can be sources of inoculum in the next season.

I just learned that Fenarimol (Rubigan ® AS, Vintage ® SC and Focus ® , from Gowan) will be taken out from the market soon.  It was due to their business decision.  The company will sell and support the fenarimol brands Vintage SC and Rubigan AS through December 2012. Gowan is in discussion with EPA to voluntarily cancel its fenarimol registrations. The distribution channel typically has 2 years from the official date of cancellation to sell existing inventory of fenarimol products. Growers typically have no time limitation to use up fenarimol products they have purchased.  (Please remember to keep and follow the label!) It is sad to loose a good product that can be an alternative option for our powdery mildew.  It belongs to group 3 in FREC code (Sterol Inhibitors or SI), thus, the mode of action is the same as other SI's, such as tebuconazole, myclobutanil, etc.

Boy, it has been a rainy month of September! If you are subscribing to Mark Chien's "Wine Grape Information from Penn State", you probably seen this, but here's a link to NOAA on the precipitation record from Irene and Lee .  It gives you an idea of how we started this month with a lot of moisture in the air.  As you can imagine, this type of weather will increase risks of having late season rots.  I have heard some people had an outbreak of Botrytis, sour rot, ripe rot, etc.  The pictures above are examples of Botrytis bunch rot.  The management strategies for these rots are discussed in the previous post .  Since temperature during these rain events were low and we have not have many days with sunlight, you may want to keep your clusters hanging little longer.   Please keep remind yourself about the PHI when you decide to apply fungicides. One of the strategies for sour rot and Botrytis management discussed was the management of birds.  Tony's group has

I thought I would wait until the rain stops to update the blog, but rains are keep coming and even when we do not receive precipitations, the air has been so damp that the relative humidity has been above 90% for a while.  It started late night on 9/4, and still going.  So far, I counted about 90+ hours of estimated leaf wetness. The temperature has been between low 60's to mid 70's.  This has been ideal condition for both Botrytis and downy mildew to develop.  As for downy mildew, your berries should be resistant to infection, thus, concern is on foliage infection.  Vines need healthy leaf areas for accumulation of carbohydrate into main trunk in order to survive the winter.  With a concern on the PHI, one of Phosphorous acid or Phosphonate materials should be a good choice.  They also provide a good kick-back activity too. I have covered Botrytis earlier in this blog, so, please click here and here for more information.  If you decided to make an application, please be aw

Irene stayed little longer than I expected in our area.  At the end of Sunday, Winchester area received a total of about 0.5 inches of rain. I was monitoring the RH for last 2-3 days, but it was below 90% (actually it was 60-70% in most of time between rains).  It was probably because of high wind due to Irene.  Based on this information, the risk of Botrytis is not high; however, as with any precipitation events, it varies dramatically even between short distances.  (For example, our AREC station received 1.2 inches or so from Irene.)  Thus, please check your local weather service. 

I hope none of you (and your crops) were severely affected by Irene.  Although southeastern part of the state saw more of it (e.g., Richmond area received 3-4 inches of rain), Winchester area was the edge of the affected area by Irene and only received about 0.25 inches of rain.