Virginia Grape Disease Updates

Thank you again for participating in our meeting. Please find two materials from today's presentation. 1) List of short PHI fungicides for late-season diseases (will open a pdf file) 2) Today's presentation (will open a pdf file). Have a good rest of the season, and hope to see you next week at the VVA summer technical meeting!!

I have updated my fungicide application template that I have been using for my fungicide guides. If you are interested in it, download it from this link.  This will open a new Google Doc page, which  says it is "View Only"; however, you can download the file. Select "File" from the top menu of Google Drive, and you will see the "Download As" submenu which has several options for the file type. Many thanks to Mr. Bob Romsey who shared the original template with me! Please note that this is just a template. Your program will differ based on what you see in your vineyard(s). Please use it with VCE's Pest Management guide or Southeastern IPM guide (linked under "Resouces"). Speaking of the Southeastern IPM guide, I created modified tables  that consist of a list of commonly used fungicides in the vineyard with their FRAC codes and fungicide resistance risks, and a template for the spray program. I hope these materials will help you organize your ...

It looks like we will see a series of rain events in the next few days. As noted in the previous virtual viticulture meetings, we had several black rot and downy mildew infection events in the past two weeks, and some people start to see the development of these diseases. Some growers asked me how long does it take for fungicide materials to be dry enough to be rainfast. It depends on your sprayer, droplet size, weather conditions, etc., but typically, I hear 1.5 hours to 2 hours are required. Some fungicide labels show the expected dry time. The other common question is about how much rain is enough to wash off fungicide materials from the plant surface. Please check the excellent articles from Dr. Annemiek Shielder ( link 1 , link 2 ). She talks about the rain fastness of some products using a rain simulator. It looks like there is a sharp drop only after 0.04 inches of rain, but after that, the material tends to stay on the surface, even if there are more precipitations. In the art...

The label of Presidio has been changed, and unfortunately, the grape was removed from the list of hosts. This means that we no longer able to purchase Presidio to control grape downy mildew. If you already have it, it is still legally OK to use it for the grape, as long as you keep the original label. (and if you do, please make sure to mix with another mode of action such as mancozeb, captan, copper, since the active ingredient for Presidio is known to have the fungicide resistance issue, and required by the label to mix.)

Our reds broke buds, and whites have about 1-inch shoot growth on it today, and more rains in the weather forecast. It is time to think about Phomopsis! What happen from this point to pre-bloom is a relatively simple spray program to manage Phomopsis, downy mildew, and powdery mildew. During the early part of the season, I typically recommend a mix of mancozeb and sulfur or copper by itself. The reason why I recommend mancozeb now is because it works on so many different diseases (including Phomopsis which is the main target for us), plus, mancozeb has a 66-day PHI and a limit on the amount of mancozeb to be used in a year (e.g., 24 lb (or 18 lb of a.i) if you Dithane DF). Thus, I would like to use mancozeb-based product early in the season. I have been often asked whether you should include sulfur or not. If your vineyard has a history of powdery mildew outbreak, it would be a good idea to have a sulfur in your tank mix, even at early part of the season. Although you may not abl...

In my pruning time disease considerations  (this link opens Google Drive with this year's recommendation for trunk disease management), I refer to Topsin-M as a choice of trunk disease management, especially for Botryosphaeria canker, which is very common in our area. The product has been transferred to a new company this year, and hence, there are changes in the label. [The US distributor is still the same (UPI), thus, I do not think it will affect where you can purchase the product.] If you are using Topsin-M for pruning wound protection, please update your label. You can download the new label by clicking this link  (will open Google Drive). Also, speaking of trunk diseases, I have been involved in a big research effort to develop management strategies for various trunk diseases. Please check our project page which contains not only research reports, but also extension information, such as disease keys, management guides, and economic tools to estimate the benefit of t...

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

1) What to do this and next week It looks like we have a window today for application, and after the rains over the weekend, next week looks good too. Right now, I am not too concerned about powdery mildew because it has been too cold and wet for this disease; however, next week will be nice and dry (I hope!) Thus, if you are concerned about powdery, you may need to add powdery mildew specific material (Quintec, Vivando, Torino, Luna Experience, etc) for your next application. Of course, something like Luna would be good for black rot, so, you may want to hold off until at bloom application (which may happen soon for people in the south) Also, make sure to cover for downy mildew too. Although temperature has been low, with all the rain we received, I have a feeling downy mildew pathogen can cause infection. I would use a phosphonate material (Prophyt, Phostrol, etc) at this time of the year so that I can keep the use of a big gun (Ridomil product) for at bloom application, if needed...

Due to many rain events and relatively cold weather, it looks like we are somewhat back in truck in terms of the growth stages. When shoots are about 10-12 inches long (i.e., right now), downy mildew, powdery mildew, and black rot tend to show up. Then, at bloom time, flowers and young berries will be susceptible to these diseases, and young berries are susceptible until 4-6 weeks after bloom.   In addition, Botrytis, ripe rot, and bitter rot can cause infection on flowers.   Yes, it is a lots of diseases to think about. What you need to think about is which disease(s) have been the major issues at your vineyards. The disease history of your vineyards tends to repeat itself. Downy and black rot management depend on weather condition.   I have seen cases where downy or black rot developed prior to bloom under wet conditions, and this year would be such a case, if you could not keep up with the protection. If you have concerns on downy or black rot...

Thanks again for those of you who were able to attend IPM workshops.  I hope you enjoyed the meetings, and if you have any suggestions or comments, please do not hesitate to contact me. Here are copy of fungicide updates and interactive fungicide planning presentations. 2016 Fungicide updates ( Please note: I just learned that Luna Tranquility won't be available for grape...  Too bad since it would be a good material for Botrytis management.  We still have Luna Experience, but there will be a label language change for grape.  I will post it once I learn more about it.) Interactive fungicide planning. Also, I think many of you have already participated, but there is a survey for evaluation of my Extension activities.  If you could spend 3-4 min of your time to answer it, I would greatly appreciate. (This is the same as the one Tremain sent out and I distributed at the VVA and other meetings.) https://virginiatech.qualtrics.com/SE/?SID=SV_eQGl7C8eYx23...

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!!!

The warm May pushed our vines forward rather quickly.  Many people in northern VA are about to see blooms (our 3-year old young Chardonnay vines are trace bloom), and I am sure rest of regions are going through bloom by now.  This means that many of us are in the critical time for cluster infections by downy mildew, powdery mildew, and black rot.  Bloom time is also critical period to prevent Botrytis, ripe rot and Bitter rot, because pathogens of these diseases can infect flower parts and come back later. We do have materials with kick-back activities against downy (Ridomil products, Phosphonates, etc.) and black rot (myclobutanil, etc.), but infection on flowers and young fruits can happen very fast.  Unless we have a very dry season, this is the time where you have to be proactive.  (Note: recent warm and humid night time conditions are favoring spore production of downy mildew pathogen)  Thus, what I recommend often is use of protectant materials to p...

I posted general "rule of thumb" about application (or re-application) earlier this season .  Dr. Annemiek Schilder at Michigan State University recently published a very nice write up about it. She answers many of questions we have in our mind, when the fungicide residues to be washed off from the rain, efficacy of spreader-stickers, and systemic fungicides.  Please check it out.

As usual, we start our season with rains.  It has been more than 13hr of wetness so far at Winchester with an average temperature of low 50s.  It has accounted for a low risk of Phomopsis infection, and a line of rain just passed the area too.  We will see how it will turn out over the weekend. As shoots extend rapidly in the early part of the season, the new tissues are not protected by the previous application of fungicide(s).  Keep in your mind to protect these new tissues. I often am asked about when to reapply fungicide(s) after rain.  An often discussed rule of thumb is: < 1 inches of rain: Continue with intended spray interval 1-2 inches of rain: Consider shortening your spray interval in half.  (E.g., if there is 7 days remaining for the normal spray interval, shorten it to 3-4 days) >2 inches of rain: Consider re-application soon. However, please note that it also depends on the history of your vineyard(s), cultural practice, and a...