Virginia Grape Disease Updates

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I heard from many that their fruits are ~2 weeks ahead of "average" season, and some early cultivars are already harvested in the southern VA. I should have posted this earlier, but it probably is still applicable to many of us, so, here is a list of fungicides with PHI (Pre-Harvest Interval) equal or shorter than 7 days.   (the list is the same as in 2018, I did not see any additional material with PHI >= 7 days. If I missed any, please let me know.) I cannot cover every single fungicide out there, but I tried to cover common ones. Winemaking considerations can influence fungicide uses close to the harvest too. Make sure to communicate with your winemaker(s) if they have a preference on the use of fungicides, especially copper, sulfur, and captan (I listed several copper materials because they have different PHI or REI.) For fungicides to be used on cultivars that have more than a month to go, please refer to my previous post. Please make sure to rotate mode of action...

Our Chardonnay clusters are getting larger and berries are starting to touch each other. It feels a bit early, but here are grape disease management reminders at berry touch/cluster closure stage. Botrytis gray mold: The best management practice is canopy management. Botrytis pathogen likes high humidity, thus, the poorly managed canopy that traps humidity will help them to thrive. This pathogen also needs wounds to develop spores, thus, grape berry moth and other insects plus birds need to be managed too. There is a number of Botrytis materials such as Rovral and Meteor (FRAC 2), Elevate (FRAC 17), Vanguard and Scala (FRAC 9), Luna Experience (FRAC 7 plus 3), Kenja (FRAC 7), Miravis Prime (FRAC 7 plus 12), Switch (FRAC 9 plus 12), etc. Botrytis pathogen is well known for its ability to develop fungicide resistance, so, please rotate FRAC codes!! QoI fungicides (FRAC 11) are no longer the effective material for us due to the development of QoI-resistant Botrytis isolates thro...

My colleagues and I are seeking information on sour rot so that we can develop research priorities (and hopefully obtain grants). Many of us suffer from sour rot (remember the last season?), and we need to get our heads together. If you could fill in this short survey, we really appreciate. It should not take more than a few minutes to complete. It is not just for Virginia, so, please feel free to complete the survey if you grow grapes outside of Virginia. Sour rot survey (will open a new window) Thank you!!

Of course, once I mentioned the lack of rainfall, we  (i.e., northern VA)   were hit by a series of rain. To make things more complicated, we had at least three consecutive nights of warm and humid (RH > 90%) condition prior to the rains. Humid nights encourage downy mildew pathogen to produce spores, and rains will splash spores to healthy tissues. Thus, the risk of downy mildew during recent rain events was very high. ( Note : Central VA also had two humid nights in 7/5-7/6 at the Charlottesville airport, but the chance of rain is not high until this Thursday.) There are a number of materials can be used for protection: captan (FRAC = M4), mancozeb, ziram (FRAC = M3), Revus, Forum (FRAC = 40), Zampro (FRAC = 40 plus 45), Ranman (FRAC = 21)). Mancozeb products have the 66-day PHI, but ziram's PHI is 21 days.  Another good option is a copper (FRAC = M1) material, which is more economical than other materials. Copper has good efficacy against downy mildew, and ten...

It depends on where you are, but in northern VA, we are having relatively "dry" weather this summer. We have some rain events here and there, but overall, the air is humid, but not wet. Such a condition promote powdery mildew development, so, I just want to provide a reminder on powdery mildew management. (Powdery mildew symptom on a cluster: the picture was taken this morning) Powdery mildew pathogen thrives under shaded condition  (i.e., overcrowded canopy). Thus, canopy management is a very important aspect of powdery mildew management. Chemical management options: Sulfur (FRAC = M2) is an economical option. Copper (FRAC M1) works too, but compared with sulfur, copper seems to be slightly less effective. Other options are: DMI fungicides (e.g., Rally, Elite, Mettle, Rhyme, etc, FRAC 3), Quintec (FRAC 13), Vivando (FRAC 50), Luna Experience (FRAC 7 plus 3), Topguard EQ (FRAC 11 plus 3), Rhyme, Kenja, and Aprovia (FRAC 7), Torino (FRAC U6), etc. Please make sure to...

Just a quick reminder about the 66-day PHI for mancozeb products. If you are thinking about harvest at the end of August or early September, we are getting very close to the limit. You can switch to captan or copper, but these two cannot control black rot, thus, you may need to add a DMI or QoI fungicide for black rot. At least in our area, it has been dry (relatively speaking) so, depends on where you are, you may or may not need to be concerned about black rot. I see black rot on leaves sporadically in my vineyards, but not in the level I need to be greatly concerned.

It was very nice to see you all at the meeting. Here's the content of my handout. Seasonal grape disease updates For VVA Summer Technical Meeting at Stone Tower Winery 12 June 2019 Mizuho Nita nita24@vt.edu Grapepathology.blogspot.com The critical period for cluster infection: Grape clusters are sensitive to infection by powdery mildew, downy mildew, and black rot from the time of bloom to 4-6 weeks after bloom. The length of this critical time depends on the cultivar, 3-4 weeks for American grapes (V. labrusca),  5-6 weeks for French grapes (V. vinifera), and somewhere between the two for hybrids. Please make sure that you have good coverage during the critical period. In a typical year, once we pass the Fourth of July weekend with a clean canopy, we can relax a bit. We are a week or two ahead of “normal” year, so, you may able to relax sooner this year. Downy mildew: Rainfall is not as intensive as the last year (knock on the woods!), but there are enough to driv...

This is the second part of "at bloom" fungal disease management tips. P lease refer to yesterday's post as well. The spray timings for Botrytis is at bloom, bunch closure, and veraison.  The pathogen has a wide host range and seems to be active throughout the season, but blooming time is considered as a critical timing because the pathogen can infect flowers without showing symptoms. Please keep in your mind that Botrytis is very well known for its capacity to overcome fungicides.  Thus, a rotation of mode of action groups is a very important aspect of Botrytis management. Mode of action for a particular fungicide can be found as a FRAC code, which you should be able to locate on the label.  Here’s a short list of materials for Botrytis and their FRAC code in parenthesis: Elevate (17), Scala (9), Vangard (9), Switch (9+12), Inspire Super (9+3), Luna Experience (7+3)*, Kenja (7)*, Meteor/Rovral (2), Endura* (7), Pristine* (7+11), Miravis Prime (7+12)*. The materia...

Many people in northern VA are about to see blooms in a few weeks, and I am sure the rest of the regions are about to see bloom very soon.  Bloom is a start of 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. What I recommend often is the use of protectant 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 experienced rain every weekend (and looks like another rainy weekend coming up), we need to be on top of downy mildew and black rot manageme...

It has been another rainy weekend (1.5 inches so far and still counting), and looks like next weekend will be wet again... Hopefully, this year won't as wet as the 2018 season... Hopefully, you can provide good protection before the rain, but even if you did, rain more than 1-2 inches can wash the material away from the canopy. Dr. Annemiek Schilder at Michigan State University has a great article 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. Downy mildew symptoms on the upper leaf surface 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 mi...

(Phomopsis leaf spot (plus a lesion of black rot), please note the shoot behind the leaf is showing some necrotic lesions which are also caused by the same pathogen) 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 typically takes a while to establish in the vineyard. It may take 5-6 years for Phomopsis to become noticeable if you start a new vineyard. Ho...

It's approximately 10% bud break on our 10 years old Chardonnay and about 25% on 5 years old Chardonnay. Hopefully, we won't get frosted!!

Thank you for attending grape disease management workshops at Loudoun County Extension Office. I really enjoyed the discussions we had. I also appreciate the effort Ms. Beth Sastre puts together for organizing the meeting and translating for 4 hours!! Click here to download the pdf of the slides I used in the workshop. I fixed some errors, but if you have any questions, please do not hesitate to contact me. Good luck with the 2019 season!! I will update this blog as the season goes along.

Our next grape disease management workshops are at Loudon County Extension Office. Please RSVP with Ms. Beth Sastre (flores69 (at mark) vt.edu). Por favor únete a nuestro taller de manejo de la enfermedad de la uva! RSVP con la Sra. Beth Sastre (flores69 (at mark) vt.edu). Thursday, April 04, 2019 Vineyard IPM Program (1 - 4 pm) Disease management in the Vineyard ( in Spanish/en Espanol ) Loudoun County Cooperative Extension office 750 Miller Drive, SE Suite F-3 Leesburg, VA 20175 Friday, April 05, 2019 Vineyard IPM Program (1-4 pm) Disease Management in the Vineyard ( in   English ) Loudoun County Cooperative Extension office 750 Miller Drive, SE Suite F-3 Leesburg, VA 20175

Here are my presentation slides from PSU grape disease and insect pest management workshop. Once again, I am looking for crown gall samples from neighboring states.   Please contact me when you have some (dying) vines to spare. I will come and get it. I am planning to visit PA vineyards this summer. 1) Late season rots (Botrytis, Sour rot, and ripe rot)      - I learned some people want to have a file with a larger side size: here is a "1 slides/page" version. 2) Review of trunk/vascular diseases      - Larger (1 slide/page) version

Here are slides from my presentations at UGA Seasonal Vineyard and Pest Management Conference. 1) Ripe rot research updates 2) Introduction to trunk disease diagnostic aid app and GrapeIPM.org. FYI: Our next grape disease management meetings are at Loudon County Extension Office. Please RSVP with Ms. Beth Sastre (flores69 (at mark) vt.edu). Thursday, April 04, 2019 Vineyard IPM Program (1 - 4 pm) Disease management in the Vineyard ( Spanish ) Loudoun County Cooperative Extension office 750 Miller Drive, SE Suite F-3 Leesburg, VA 20175 Friday, April 05, 2019 Vineyard IPM Program (1-4 pm) Disease Management in the Vineyard ( English ) Loudoun County Cooperative Extension office 750 Miller Drive, SE Suite F-3 Leesburg, VA 20175

Here's a 2019 version of fungicide application template. Please read the footnote for downloading onto your computer or copy to your Google Drive to use it. This template is designed to be used as a guide. You need to create your own plan based on your vineyard(s)!! If you have time tomorrow afternoon, please join us for our first grapeIPM.org training session , which will be held at Horton Vineyards from 1 PM. It would be a great excuse to visit Horton to taste their award-winning wines!

We will hold a training session for GrapeIPM.org on March 15th (this Friday) at Horton Vineyards  (6399 Spotswood Trail, Gordonsville, VA 22942). The meeting starts at 1 PM and closes at 3 PM. GrapeIPM.org is our new online database and risk assessment system which allows you to manage your pesticide records and planning. We introduced it to select growers in 2018, and we are extending the invitation to more growers this year. You can assign multiple vineyards or blocks (whichever you wish to call).  The system has a pre-made list of commonly used fungicides (we are working on insecticide now), thus, what you need to do is pick the one you have in your inventory, and enter in the system's calendar.  If you happen to use not-so-common pesticides, we are working on an interface that allows you to enter your own. You can enter the area to be applied and the size of your sprayer, and the system will give you an estimate of how much you need to mix in your spra...

At this time of the season, I am often asked about an application of fungicide(s) to dormant vines. I totally understand that you want to do something before things get busy. A dormant application of lime sulfur (10% in our study, or 1% of a newer product called Sulforix in a study done by Dr. Annemiek Schilder at Michigan State Univ.) should be effective against Phomopsis and/or Anthracnose . We also tested cupper, but it was not effective. However, the efficacy of the application is not strong enough to allow you to skip any preventative fungicide applications to be sprayed soon after bud break. (i.e., even with a dormant application, you still need to protect your shoots when they emerge.) With the corrosiveness of lime sulfur, I feel that it is not worse the money and time, plus, it will be another application of a fungicide, which we try to reduce. It is much effective to spray mancozeb or captan soon after bud break. Thus, I would recommend a dormant application ...

Captan, which we use extensively to manage downy mildew, Phomopsis, ripe rot, and other grape diseases, is currently under review by the EPA. In order to keep captan as one of our tools to control grape diseases,  please respond to the EPA's registration review page to post your comment  (will open the EPA page). With increasing cases of fungicide resistance with newer products in our region, it is very important for the majority of commercial grape growers located east of the Rockies to keep older multi-site materials such as captan to be used as a backbone of the spray program.  Also, please forward the message to other producers and stakeholders who should respond to the need for this fungicide in our industry. 

Here is a list of upcoming meetings. Please note that there are two meetings on March 15th.  GrapeIPM.org introduction and training session will be held at Horton Vineyards from 1:00 PM. Friday, March 01, 2019 Dormant Pruning Workshop Hamlet Vineyards, Bassett VA Free, registration required:  https://www.eventbrite.com/e/dormant-pruning-workshop-for-vineyard-growers-tickets-55660249304 Thursday, March 7, 2019 Dormant Pruning Workshop and Competition (1pm - 4pm) English and Spanish speakers welcome Sunset Hills Vineyard Free, registration required: https://goo.gl/forms/sNI1ULt5s3H41y7W2 Thursday, March 7, 2019 Ag Labor Forum Longwood University Registration required Friday, March 15, 2019 New Grower Workshop Abingdon Vineyard  https://www.eventbrite.com/e/new-and-advanced-grower-workshop-tickets-57447751772 Friday, March 15, 2019 A new tool for vineyard management, grapeIPM.org: Introduction and Tra...

It was very nice to see you all at the VVA meeting! Here are the slides from my presentations (in a pdf format). 1) Grape disease management workshop 2) Ripe rot research updates I will post a list of upcoming VCE meetings in a few days.