Virginia Grape Disease Updates

Thank you for who attended NJ's "Grape Expectations" meeting two weeks ago. (I think it is a very cool name for an Extension meeting.) Sorry for not able to post my presentation sooner. I have been out for other meetings. Click here for slides from my presentation. It will open a PDF file on Google Drive.

Here are slides from my student's presentations. The link will open a PDF file on Google Drive. Please note that many of data presented here are still preliminary and we are working on publications. 1) Wong and Nita " Evaluation of Rhizobium vitis ARK-1, A Biological Control Agent For Crown Gall of Grapevine, Using R. vitis Isolates From Virginia Vineyards " 2) Oliver and Nita " Laboratory and field fungicide testing for control of Colletotrichum species isolated from Virginia vineyards "

Thank you again for those of you attended one of my sessions. Here are links to my presentations. It will open PDF files on Google Drive. 1) Interactive grape disease management 2) Advanced topic in grape disease management: Fungicide resistance Please note that we will have more meetings coming up: 16 March 2018 Pruning workshop at Breaux Vineyards (Northern Virginia) 17 April 2018 Vineyard IPM workshop at Early Mountain Vineyards (Central Virginia) 6 June 2018 “Beginner’s” Grape Growing workshop Virginia Tech’s AHS Jr. Agricultural Research and Extension Center, Winchester VA We hope to see you there!

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.)

Here's this year's handout for pruning time disease considerations  (this link opens Google Drive with this year's recommendation for trunk disease management). As I noted in this handout, the first line of defense against trunk diseases that may infect through pruning cut is a cultural control. Make sure to pick dates when you are expecting several days of dry weather. In this handout, 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 in 2017, and there are changes in the label. [Note: 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). If you are pruning, and wondering whether you can protect pruning ...

Looks like we will likely to have another round of rain from Hurricane Irma sometimes next week. Just a reminder that we do not have any curative materials for Botrytis and other late season rots. In order to obtain better results, you need to protect your vines before the rain! Please see the previous post for disease management tips and the list of low PHI materials for each diseases. Also, it is very important to keep FRAC codes rotated!

At Winchester, night time temperature in recent few days is getting pretty low to the point that relative humidity during the night is close to 100%. In addition, we are looking at a thunderstorm forecast tonight that will bring high relative humidity. These conditions favor downy mildew development because downy mildew pathogen prefers to produce spores under dark, humid conditions. At this point, you do not need to worry about downy mildew infection on clusters; however, they can still infect leaves. Often time, you will initially see infection on the top of the canopy because younger leaves are more susceptible than older ones. Losing the top leaves and laterals are not a big deal; however, once the infection gets severe, it can defoliate many leaves rather quickly (as in the picture above), and that can affect maturing process. As usual, it is much better and easier to have a preventative program than trying to play the catch-up game. There are many good protective mater...