Virginia Grape Disease Updates

It has been pretty wet week so far. At Winchester, we observed about 11 hours of wetness on the 26th with an average temperature of 64F, 50+ hours (and counting) from the 28th to today with an average temperature of 61F. It is certainly long and warm enough for Botrytis infection. Whether we require a fungicide application for Botrytis or not at this point depends on several potential factors. The first one, of course, is whether you had a previous application or not. If you had a previous application to cover these rain events, you probably do not need to be concerned much. The second one is a time to harvest. If you still have several weeks to go, you may want to consider an application, but if you will harvest within a few days, I am not sure an application of fungicide will help you much since we do not have any curative materials for Botrytis. Whatever we spray at this point will be good against future infections, but not the infection happened already. The third is cultivar...

Maybe I should keep posting that rains are coming... Each time I do, it looks like rains disappear. ;) If you have not subscribed to the email list of Dr. Tony Wolf, who is our viticulturist, please do. It always have a wealth of information. In his latest newsletter, he explores potential reasons why some of cultivars are stalling on ripening process this year. Our Chardonnay is still stuck at 19 Brix or so too! The below is a link to his newsletter, but it typically take several days for the newest one to appear. Thus, the best way is to subscribe to his email list (the instruction for subscription is listed on the page too). http://www.arec.vaes.vt.edu/alson-h-smith/grapes/viticulture/extension/VN_options_index.html

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

I heard that some of early cultivars are ready to be picked on 7-10 days.  Looks like no tropical storms to worry, yet... (crossing my fingers!) There have been frequent thunderstorms went through our area, and some of them (like the one we had last night) resulted in a significantly long wetness event (8 hours). These wetness events, especially the one happens overnight, are preferred by downy mildew pathogen since they produce spores in dark, moist conditions. Please check my previous post on late season downy mildew . As usual, protection is the best approach.  If you have seen some downy mildew on foliage, it would be best if you can mix a protective material (e.g., copper, captan) with a phosphonate (Prophyt, Phostrol, etc). If there is heavy downy mildew already happening, please do not use Ridomil (metaxel) products because they are known to be overcame by the downy mildew pathogen. Some of reds are probably going through veraison, which would be a good timing for...

As many other parts of VA, we have been experiencing thunderstorms running through our area in the past week for so. Yesterday, we had about 9 hours of wetness with an average temperature of low 70's, then followed by a very humid night with an average temperature of mid-60's. These conditions are conducive for downy mildew development. Please check the previous posting for more information on downy mildew management. Also, as veraison approaches near (or happening for some cultivars), please check 12 July posting on late season disease management.

At Winchester, we had 8 hours of wetness observed on last Thursday, then there are several short rains/thunderstorms. Moreover, the night time relative humidity has been fairly high (> 95%) in the past few days. These conditions favors downy mildew development because downy mildew pathogen prefer 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 see infection on the top of the canopy around this time of the year because younger leaves are more susceptible than older ones. Once infection gets severe, it can defoliate infected leaves. As usual, it is much better and easier to have a preventative program than try to play a catch up game. There are many good protective materials for downy mildew, such as Revus products, Zampro, Forum (Please note that these three share the same mode of action), and Ranman. In our small trial, we found that fixe...

Most of us are about to finish critical time when clusters are susceptible to infection by downy mildew, powdery mildew, and black rot.   This critical time varies by varieties, but in general, 4 to 6 weeks and 3-4 weeks from bloom for V. vinifera and V. labrusca species, respectively.   After this critical period, you should be able to relax a bit because these pathogens no longer able to cause disease on berries. So, what’s next?   As usual, disease dynamics really depends on environmental conditions, cultivars grown, and cultural practice you employ, but in general, this is the moment when you will be thinking about late season diseases such as Botrytis, ripe rot, bitter rot, and sour rot.   The spray timings for Botrytis is at bloom, bunch closure, and veraison.   The pathogen seems to be active throughout the season. The main reason we recommend application of a Botrytis specific material at bunch closure is that this mos...

Just an update on yesterday's post: At Winchester, AREC, a total leaf wetness hours was 29 hours, with an average temperature of 67F. Thus, this rain event was warm and long enough for both downy mildew and black rot. Also, it was long enough for Botrytis as well. For the details of downy and black rot kick back activity fungicides, please refer to yesterday's post.

A cool and wet Fourth of July weekend resulted in a very long leaf wetness hours. So far, more than 12 hours of wetness has been recorded at Winchester AREC, and at this rate, it will go on over the night (= potentially it will be a longer than 24 hours of wetness event). As noted in my previous post, the April frost event(s) probably resulted in a prolonged bloom period. Because of that, I have a feeling that some portions of clusters of many of cultivars are still under a critical period for downy mildew, powdery mildew, and black rot for at least one more week. If your vines were protected with materials such as mancozeb (for downy, and black rot), Revus, Forum, Zampro, Presidio, or Ranman (for downy), Luna Experience, Rally, or other DMI (for black rot) or Abound, Pristine, or other QoI (for black rot), you should not worry too much about it. However, if your vines were not well protected, (e.g., last application was more than 12 days ago, or you have missed some of protective ...

Photo: we have started to see powdery mildew on clusters. I hope you are not! Looks like series of thunderstorms are hitting various part of the state this week. Just a reminder that due to April frost events, some of us experienced extended bloom. This not only means potential lag in harvest time for these late clusters, but also, an extended critical period for seasonal diseases. Grape clusters are susceptible to black rot, downy mildew, and powdery mildew from bloom to 4-5 weeks after bloom (3-4 weeks for American grapes). Thus, this is the time I want you to be on top of the game (i.e., nice coverage, 7-10 days interval, good selection of fungicides to be applied). Many growers told me that if they are clean around the Fourth of July weekend, you don't expect outbreak of black rot, downy mildew, and powdery mildew. I generally agree with their assessments since in many years, bloom happens late May or early June. However, this year, bloom started the first week of June,...

Here's my handout from last week's meeting at Stone Tower Winery . Thanks for those who attended the meeting! It looks like we may have rains here and there this week. Since we have not had significant rains in the past week or so, the risks of downy maybe low, but most of us are still in the middle of critical period for cluster protection. Please refer to my at bloom post for more details on disease management tips for this time of the year . Once we pass this period, we can relax a bit, in terms of fungal disease management.

At Winchester area, we ended up having a pretty good weekend. There were several periods with rain, but it was not as extensive as the forecast. We received about an inch total over 2-3 days. However, it looks like the central VA received more rain than we did. I would like to share a question I received from a grower today. "With all of the rain events we have had lately and bloom being an important stage for fungicide application Should we spray after a significant rain event before the recommended 7-14 day interval? Specifically, I applied fungicide June 3rd and received quick but heavy rainfall on the 4th and 5th. Riding through the vines it looks as though there is still chemical residue on leaves and clusters. Can I base a decision off of this observation?" It really depends on what you have sprayed, what we are expecting in the next few days, how the vines are maintained (shoot thinning, etc), cultivars, etc, so, I cannot give you a quick answer. Typically...

Our Chardonnay vines are getting close to full bloom, and of course, we are expecting more rain over the weekend. Just an another reminder that from bloom to 4-5 weeks after bloom is the critical period for downy mildew, black rot, and powdery mildew infection on clusters, and at bloom application is very important one for Botrytis management.  Please see recent post about the at bloom fungicide application consideration as well as recent updates on fungicides. This would be the timing where you will thrown in some good materials into your tank mix! It is much easier to protect the vines than try to play a catch up game after disease outbreak,

I noticed that some of our 'Cheloir' vines are in trace bloom and also it has quite a bit of black rot. As I suspected, the cold rains we received were long enough for pathogens beyond Phomopsis to be able to infect vines. If you have not seen black rot lesions on leaves and shoots, the pictures below are good examples. If you click on them, it should open a larger picture. Please note the small dots on these lesions. These are fruiting bodies that contains spores. Once again, most of us will be seeing bloom in the near future, and it will be a start of critical period for so many diseases . Please be on top of your game (shoot thinning, canopy management, and of course, fungicide applications). Mancozeb, as well as both DIM and QoI fungicides are very effective against black rot pathogen. Looks like we are expecting some rains again next week! Black rot on leaves  Black rot on shoots and rachis

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...

Well, it looks like we will see more rains coming in next week or so. Sounds like a typical start of the season for VA vineyards, doesn't it? Since most of vines have 2-10 inches of shoots, our main focus will still be Phomopsis , especially if your vineyard(s) experienced Phomopsis in the past.  At Winchester, we are experiencing 27+ hours of wetness with the average temperature of 48F or so. This will be a low Phomopsis risk event, and counting. Plus, especially if you had a serious downy mildew issue in the past season, it may not be a bad idea to think about downy mildew because the next series of rains for this weekend and early next week may happen when air temperatures will be in 60's and 70's.  As for Phomopsis, a protective spray of mancozeb, captan, etc. is pretty much the only mean of management, but we do have some options for downy after the rain event. So, if you did not spray before this series of rains, but you are lucky enough to have a window for a s...

Several growers contacted me recently to discuss about disease management after recent frost events. Here are my take on it. 1) If you have some damages on your shoots/buds. As usual, you work with the growth of the vine, but not with the calendar dates. If you have lost a lots of growth from the primary buds, you may have to start over your spray program.  If you have mixed growth from the primary and secondary buds, you may need to adjust your spray program based on what may come from the secondary buds, especially around bloom. Flowers from the secondary buds may lag behind, thus, you may need protect flowers for a longer period of time. 2) If you have extensive damages on your shoots/buds to the point that you may not able to expect crops. Based on what I heard, we are not seen this scenario this year. However, if you happened to have the major issue from the frost events, well, first of all, I am sorry.  Second, you still need to have some level of disease managemen...

As with many other places in the VA, we were suffering from frost damages.  We experienced several near freezing events this year, and most notably, a few hours of 25F on Thursday morning. Our younger Chardonnay planting (4th leaf) had a bud break around 4/1, and being suffered more from it.  I estimated about 80-90% of emerged shoots are now gone. Our older Chardonnay (8th leaf) is about a week behind, and my visual estimate as of yesterday was about 25% loss.  Some buds/shoots look like they are surviving, but I am not sure how it will go after tomorrow morning... There is a very nice blog post about spring frost from Dr. Michela Centinari at PSU.  If you are interested in, please follow this link. The other items I noticed in our vineyards is damage from climbing cut worm. For us, it always starts from the Eastern side of our vineyard which is facing a small patch of wood.  If it is a warm weather, I would spray for it, but I think I will wait ...

Our 7-yr old Chardonnay vines are in bud swell stage, and others are tagging along.  It looks like we will see bud break in a week or two. One of diseases you need to consider this time of the year is Phomopsis cane and leaf spot .  It causes minor leaf spots, but more importantly, it can cause necrotic lesion on shoots and rachis.  It also causes berry infection; however, it is not common with wine grapes because of our spray programs.  Materials for black rot and downy mildew are often effective against Phomopsis, thus, the coverage for these diseases are also working as management of Phomopsis, especially later in the spring/summer. Phomopsis takes a while to establish in the vineyard; however, once it is established, it is difficult to get rid of this disease.  Some varieties, such as Viognier and Seyval blanc, are more susceptible to Phomopsis than others.  Phomopsis tends to become noticeable as a vineyard gets older becaus...

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...

There are several extension activities in the next few weeks that you maybe interested in. 1) IPM workshop at Early Mountain Vineyards This will be a full day IPM workshop to cover viticulture, entomology, weed science, plant pathology, and legal and safety updates. This will count towards VA private pesticide applicator license hours (full credit for category 90). Date: Feb. 16th 2016.   Agenda 9:30 Introduction and overview of workshop 9:45 Viticulture updates – Tony Wolf 10:15 Worker Protection Standards- Roberto Quintero 11:00 Entomology updates - Doug Pfeiffer 11:45 Weed science updates - Jeff Derr 12:30 Lunch ( please bring a lunch ) 13:15 Laws and regulations - Roberto Quintero 14:15 Pathology Updates- Mizuho Nita 15:00 Interactive Scheduling – in teams 16:00 Meeting Adjourns   2) Interactive Integrated Grape Disease Management workshop at Dobson, NC This will be a half-day IPM workshop that focus on grape disease management and legal and safety updates. Thi...

Here are handouts from my presentations from the VVA meeting. 1) Slides from "Interactive Grape Disease Management Workshop" 2) Results from the "planning session". Please note that this is the results of answers from randomly selected people, and I am providing this as a note from the workshop.  Although it looks "OK", this is not what we recommend. 3) Slides from "Biology and Management of Grapevine Crown Gall" It was very nice to see you all at the meeting.  As usual, I really enjoy talking to all of you! If you have missed the VVA, there will be two meetings that we will host: 1) IPM workshop at Early Mountain Vineyards on 16 Feb from 9:30 AM 2) Interactive grape disease management workshop at Surry county Extension Center (210 North Main St., Dobson, NC 27017) on 18 Feb from 1:00 PM. I will post details of these meeting in a few days.

Upcoming meetings: A. Virginia Cooperative Extension and Virginia Tech will offer pruning workshops in Central/Southern Virginia (Amherst) and Northern Virginia (Winchester) this January. Beginning grape growers and experienced grape growers are invited to either workshop. The content will include a review of these topics: ·       grapevine dormant pruning ·       grapevine cold hardiness ·       disease management at pruning ·       pruning as a component of canopy management We will then go out to the vineyard for guided practice pruning grapevines before the meeting adjourns.   Please bring pruning shears and prepare to be outside; rain or shine.   Pruning Workshop Schedule for 2016: Date / Time:     12 January 2016     / 1:00 – 3:30 pm Lazy Days Winery 1351 N Amherst Hwy, Amherst, VA 245...