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Many of you are about to be done with harvest and some may still have a few more weeks to finish this rainy season. This is a reminder for disease management after harvest. The main reason for you to keep your vines clean after harvest is for winter preparation. Grapevines need to store carbohydrate to survive the cold temperature during the winter. If there is not enough foliage on the vine, it may increase the risk of winter injury. The main target diseases are downy mildew and maybe powdery mildew. I do not typically worry about powdery mildew at this late in the season, unless you already have an on-going outbreak that started a few months ago. Downy mildew is common after late-August in our area and severe infection can result in defoliation. Therefore, in a typical year, downy mildew is the one that I would like to control after harvest. Since it will be after harvest spray, you do not need to worry about the PHI (pre-harvest interval). Thus, you can apply a combination of ma...

I received several emails and phone calls concerning spray before the upcoming hurricane Florence. Hopefully, we will have a window of opportunity to apply materials. Looks like we have a break from rain starting tomorrow for maybe 1.5 to 2 days. Here is the list of materials with low PHI (same as the one I posted last month). Just FYI: here are previous posts about... Late season downy management Botrytis gray mold management Once you have about 1.5-2 hours for the materials to dry after application, that will be sufficient for them to stick to the leaf and cluster surface. Good luck!!

At Winchester, the night time relative humidity has been still very high, close to 100%, in nearly every nights in the past three weeks. In addition, we have been observing rapid development of thunderstorms, pretty much every day in the past few days. I know I sound like a broken record, but these conditions favor downy mildew development because downy mildew pathogen prefers to produce spores under dark, humid conditions. Then spores will be spread via rain. 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. Knowing how wet this year has been, it is probably wise to be proactive on dow...

Powdery mildew colonies at the center of two leaves in the picture With this wet season, what we think most are downy mildew, black rot, Phomopsis, and Botrytis. Powdery mildew is often associated with a dry season, partially because this pathogen does not require rain for its infection process. However, what they also like to do is grow on shaded leave because they are sensitive to the UV radiation. With very clouded canopy from strong growth triggered from heavy water input (= rain), there are lots of leaves shaded by other leaves. Well, at least that is true in my vineyards... Sure enough, when I took a look at these leaves, I found powdery mildew colonies.  You can see a small white fuzz (= powdery mildew colony) on two leaves in the picture above. Note that how the leaves are shaded. We have a fair number of options for powdery mildew management. Sulfur (FRAC = M2) is an economical option, and there are range of products with different modes of action (= FRAC code).  Exam...

Although our bud break was about two weeks behind of a typical year, the wet and hot 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 the critical period to prevent Botrytis, ripe rot, and bitter rot, because pathogens of these diseases can infect flower parts and develop symptoms later. With all the rains we observed, many people are concerned about downy mildew and black rot. In our vineyards, I did not see much sign of downy, but there are many leaves with black rot. It is probably because we did not have major downy mildew outbreaks in past three years. We do have materials with kick-back activities against downy (Ridomil products (FRAC=4), phosphite (FRAC=33, Prophyt, Phost...

As if almost a week of thunderstorms and rains was not enough, it looks like we are expecting even more rain in the coming week. Hopefully, you had a good protection before the rain, but even if you did, rain more than 1-2 inches can wash the material away from the canopy. Please see the article from Dr. Annemiek Schilder about rain and wash off of fungicide . Her work suggests that although only a 0.04 inch of rain can wash a certain percentage of a material from the leaf, it takes about 1-2 inches to actually having a negative effect on the efficacy since the rate you apply is typically much higher than the threshold for the efficacy of the material. When we have the next chance of application, what material(s) should we apply? I think many of us are about 2-4 weeks away from the bloom, so, the major concern is downy mildew. If you think you have missed the window (i.e., there were more than 2 inches of rain from the last application of a fungicide against downy mildew, or it has bee...

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!

In a typical year, the fourth of July weekend is the time the critical period for cluster infection by downy mildew, powdery mildew, and black rot will end for many of us because it will be about 5-6 weeks after bloom. (Bloom this year was about 1-2 weeks ahead of typical years, so, this week maybe it for 2017.)  This critical time varies by varieties, but in general, 4 to 6 weeks and 3 to 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 are no longer able to cause disease on berries. Plus, powdery mildew tends to slow down because it is not very active under hot condition (> 90F). So, what’s next?  As usual, disease dynamics depends on environmental conditions, cultivars, and cultural practices you employ, but in general, this is the moment when you will be thinking about late season diseases such as Botrytis, ripe rot, bit...

As of today, it is about 10% bloom at our Chardonnay plots. Since bud break was about 2 weeks ahead of a typical year, things are moving along as we would expect. Of course, bloom in VA almost always has to happen in rain... As for bloom time disease management consideration, please refer to the previous post. From this point on, 4 to 5 weeks will be a critical period for management of downy mildew, powdery mildew, and black rot. Please make sure to keep your vines covered. Once again, providing a protection is much better and easier than playing a catch-up, especially if it comes to grape disease management in VA. You can use protective materials such as mancozeb, copper, and sulfur as your backbone, and add more specific (and often locally systemic) materials. Some of these materials have efficacy against multiple diseases (either by itself or through the combination of two materials). Examples are DMI, aka SI (FRAC = 3), e.g., Rally, tebuconazole, Mettle, etc. Inspire super is a...

Some shoots of our vines are about to reach the second catch wire, but I saw many that were still about 10-12 inches too. It looks like series of rain during the month of April drove developments of black rot and Phomopsis. Although it was not severe, I found several vines with leaf lesions of black rot, and a few vines with Phomopsis. Tan-colored lesions are symptoms of black rot. If you click the image, it will open a larger file where you can observe fruiting bodies (tiny black specks) within these lesions. It is a bit difficult to see, but, please note the holes on the upper picture (in the blue circled area). The lower picture shows more characteristic leaf spots of Phomopsis cane and leaf spot. For management tips, please refer to my  around bloom disease management consideration post.  Please remember that clusters will be susceptible to black rot from bloom to 4-5 weeks after bloom. Looks like Winchester area is expecting chances of rain on Friday, Monday, and the...

Many of our vines at VT's AHS AREC are about to reach the first catch wire and going strong. When shoots are about 10-12 inches long, 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 until 4-6 weeks after bloom.  In addition, Botrytis, ripe rot, and bitter rot can cause infection on flowers.  Thus, you need to consider multiple diseases management. However, you probably do not need to manage all with expensive materials. 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 because of the environmental conditions at your site and availability of spores from previous infections. Downy and black rot management depend on rains.  I have seen cases where downy or black rot developed before bloom under wet conditions. We receive a little fewer rains than last year, but it is always ...

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 able to s...

Our Chardonnay and some of the hybrid vines are in bud swell stage as of this week, and others are tagging along.  It looks like we will see bud break very soon with warmer temperature coming up next week. One of the diseases you need to consider this time of the year is   Phomopsis cane and leaf spot .  It causes minor leaf spots, which is more obvious to our eyes, but the more important damage is caused by necrotic lesions on shoots and rachis. It also causes berry rot; 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 fungicide coverage for these diseases is also working as management of Phomopsis, especially later in the spring and early summer. Some cultivars, such as Viognier and Seyval Blanc, are more susceptible to Phomopsis than the others. Phomopsis takes a while to establish in the vineyard. It may take 5-6 years for Phomopsis to become no...

It was very nice to see you all at the Weekend Warrior Grape IPM workshop. I think we had a very good time with lots of discussions. Hopefully to see you at other meetings. Here is a list of materials that we covered during the meeting. Prioritization in vineyards (Tremain Hatch) VCE overview (Mark Sutphin) Grape weed management (Tremain Hatch on behalf of Dr. Jeff Derr) Interactive grape disease management (Mizuho Nita) Fungicide application template (will open a Google Drive spreadsheet, in order to save, click "file" and select "download as..." Please remember that this one is just an example. You need to come up with your own!) Please note that there is another version, under "Resources" on the right-hand side of this blog. It is in a different format, but essentially the same type of tool. Template used in the exercise (pdf) List of chemical with FRAC codes  (pdf)

I have updated my fungicide application template that I have been using for my fungicide guides. If you are interested in, it can be  downloaded from this link . (will open a new Google Doc page) Many thanks to Mr. Bob Romsey who shared the original template to me! NOTE (8 march 2017): It says it is "View Only", but you can download the file. If you select "File" from the top menu of Google Drive, you will see "Download As" submenu which has several options for the file type. (I should have mentioned it when I posted. Sorry!) 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 (linked under "Resouces"). I have been migrating my fungicide guide to an online database, but it won't come alive until late this year or 2018, thus, refer to either the PMG or Southeastern IPM guides (also linked under "Resources") for your reference ...

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 your ...

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 most likely to be ...

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 mate...

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, but I s...

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.