Virginia Grape Disease Updates

Presentation slides Thank you to those of you who were able to make it to the meeting today. Here are slides from today's presentation (open PDF).  Up-coming meetings Eastern Section American Society for Enology and Viticulture annual meeting (7 – 8 July): The ASEV/ES meeting will occur on-line this summer. See https://www.asev-es.org/ for details on the meeting, which will include research presentations and a panel discussion entitled “Future Grape Cultivars for Eastern North American Growers”. Eastern Viticulture and Enology Forum (13 July): The July 13th meeting is the next of a series of 4 virtual meetings organized by viticulture and enology extension specialists at Penn State, Cornell, and Virginia Tech. In addition to regional round-ups of seasonal progress, specialists from around the eastern US address pre-submitted questions from participants. Registration instructions and additional information about the meetings can be found on the attached Word document. Virginia Viney...

It looks like we all received much-needed rains, which is good for vine growth. However, since most of our vines are still within the critical period for cluster infection by downy mildew, powdery mildew, and black rot (~ until 6 weeks after bloom for V. vinifera , ~ 4 weeks for V. labrusca ), it also means that we may have had risk events for disease infection. Since the month of May was dry, I think the overall disease risk is low for downy, black rot, and other diseases that are driven by rain (e.g., ripe rot and Botrytis), but I just want to go over recent NEWA outputs.  Disease risks from the recent rain events Westfield (Close to Bristol, VA) It seems that the southwest VA received quite a bit of rain over the past two weeks! I would think many cultivars are close to the end of the critical period, but if you are concerned, a DMI fungicide and a Ridomil or Phos-acid product are effective for black rot and downy mildew, respectively. These materials can be applied a few days a...

Just a quick note that recent rain events were risk events for downy mildew based on the NEWA DMCast model. It seems that northern VA received more and longer rain events. In addition, we may see more rain toward the end of next week. DMCast results at Crozet station (green cells indicate downy mildew infection events) DMCast results from Winchester station Since we have been experiencing a very dry season, I was not really thinking about downy mildew. However, during recent vineyard visits, I have noticed downy mildew on leaves, and sure enough, I saw some downy mildew lesions on leaves in one of my research blocks too. Early downy mildew lesions may not be very obvious. If you are due to spray soon, grow downy mildew susceptible cultivars (e.g., Chardonnay, Vidal, etc.), and/or have seen a considerable amount (or duration) of rain recently, it may be a good idea to include a Phos acid material (e.g., Prophyt, Phostrol, Agri-Fos, etc.) in the tank mix as insurance. Please note that if...

Recent cooler weather seems to have slowed down vine development, but it looks like vines in the south are about to bloom. Bloom is a start of the critical time for cluster infections by downy mildew, powdery mildew, black rot, Botrytis, and ripe rot, because pathogens of these diseases can infect flower parts and develop symptoms later. What I recommend often is the use of protective materials to protect tissues for 4-6 weeks for V. vinifera varieties, and 3-4 weeks for V. labrusca varieties, which should translate into 3-4 sprays for V. vinifera , and 2-3 sprays for V. labrusca .  If you have hybrids, they are somewhere in between, so, 4-5 weeks to be protected.  As usual, please make sure to rotate mode of action (= FRAC) groups. Since we have not seen many rain events, I think powdery mildew will be the primary target for many of us. But please check your local weather to make sure, some downy mildew susceptible cultivars may still show downy mildew, especially, if there...

Since the past winter was more or less steady and mild, in terms of temperature fluctuations, there are less likely that many of us saw the minimum temperature at 15F or lower. For example, at Winchester, we saw 14.5F on the 21st of February, and that's it for this winter. The risk of Pierce's disease will increase with a warmer winter. I.e., less than three nights with a minimum temperature of 15F or lower will decrease the risk of Pierce's disease.  Thus, especially people in the south and eastern part of the state may need to prepare for the management of sharpshooter leafhoppers, which are the vectors of Pierce's disease. Some growers in the eastern VA use insecticides for sharpshooter leafhoppers from May to June, so, I thought it is probably a good idea to sent out a reminder.  Entomology is not my area of expertise, thus, I will copy the information from our Pest Management Guide , page 8. In some vineyards in the eastern part of the state, sharpshooter leafhop...

 Thank you to those of you who were able to join us today. Here are some of the items we discussed. Slides from today's presentation (will open a pdf file in a new window) RSS feed address for this blog (I posted under "Resources" too) You can also subscribe via email using the menu showing on the upper left part of this blog. Google will drop the email subscription service in July, but I will come up with another way to send you reminders. Thus, if you wish to be included after July, please go ahead with the subscription service. Link to my grape disease management workshop presentation videos. Please note that the closed captioning is most likely not working. I created CC with the Canvas site we used in the workshop. If you wish to watch them with CC, please send me an email so that I can send an invitation to Canvas site. Unfortunately, I don't have time to work on YouTube version right now. I will focus more on YouTube version next year. I will keep it available f...

Upcoming virtual vineyard meetings The viticulture group at the AHS Jr. AREC will be hosting a series of four monthly, on-line viticulture meetings starting Thursday, 22 April 2021. The content of each meeting will vary somewhat and will involve extension specialists who will provide seasonal updates on vineyard management, pest management topics, and emerging weather, pest or disease issues. An initial topic of each of the 4 planned meetings will be a statewide grape development roundup gathered from our “sentinel vineyard” cooperators located around the state. Each meeting will last about 2+ hours, starting at noon.  At this point, the meetings will be on-line, but stay tuned for at least one on-site meeting which we plan to host at the AREC in late-July.  The meeting dates (noon start) are: 1)     April 22, 2021 12:00 PM (EDT) Register in advance for this meeting: https://virginiatech.zoom.us/meeting/register/tZ0pceigqTMrGdOSA5D6uvJUEfYaVZKLVER7 After registe...