Virginia Grape Disease Updates

Please see the message below from Dr. Sara Spayd, who is an extension viticulture specialist at NCSU.  The information is probably more applicable to people in the southern VA, but we have not really seen cold temperature in the northern VA either. While we can enjoy outdoor activities in the middle of December, this warm weather is bit concerning for grapevines.  Let's hope for a gradual temperature drop in the near future... -- Please pass this on to all grape growers: I know this beautiful weather is tempting, but please DO NOT PRUNE - even hedging. Pruning helps to stimulate vine growth. I would not be at all surprised if you see grape buds in some degree of bud swell, particularly the European bunch grape varieties. Those varieties have very little chilling requirement and it was likely met in the few cold days that we have had.  The short predicted cooling pattern for this weekend will do little to harden the vines and buds for any potential cold...

It was very nice to see you all at the beginner's workshop held today at AHS AREC.  Here are: 1) my presentation (Google drive will open) and 2) disease management guide for non-bearing vines. I hope to see you guys in the future!!

With this week's precipitations that we (including many meteorologists) did not anticipated last week, some of you have contacted me to seek options for the late season application, especially for red-fruited cultivars that need to stay on the vine for a few more weeks.  Here's a table for late season fungicide options, with materials that has 7 or fewer PHI (it will open Google Drive's spread sheet).   The efficacy information is based on our PMG, which can be downloaded from the right hand side of the blog.  (It says 2014, but the file is updated to 2015).  Hopefully we will see the sun soon! Good luck with the rest of the season.  It's almost done!!!

I have heard from several growers that they are seeing downy mildew despite the fact that they have not seen much precipitations.  It could happen because of the humidity, especially during the night.  Warm, humid, and dark condition (just like we have been having during the last few weeks) promotes downy mildew pathogen to produce spores. In addition to these conditions, we had lines of rain storms passed in our areas in the past two days. The length of wetness due to these storms were probably long enough for downy mildew pathogen to cause infection. So, just a reminder.  If you have seen downy mildew, and you have not applied any protective material (captan, Revus, even phosphorous acid products) in the past 10 days or so, you may want to consider a rescue application of a phosphorous acid product to reduce the risk of infection that might have happened in the past two days of rains.  (Note: If you are considering harvest in a few days, I would wait until harv...

Dr. Wayne Wilcox at Cornell University wrote an article on sour rot management on " Finger Lakes Vineyard Notes ". (The link will open a pdf file)  Please check it out.  Results from his research group is showing that 1) good canopy management matters, and 2) management of insect (fruit flies) seems to have a big impact on the development of sour rot.  Since their regions do not have issues with spotted wing Drosophila (aka SWD), even regular fruit flies, which cannot damage grape skin, can still aid transmission of sour rot pathogens.  I know some of us in VA have been managing SDW in the past few years. If you have managed SWD and have seen lower level of sour rot, please let me know.

Now the season is wrapping up, and one of questions I get often is “when to spray what to protect your crop at the last stretch”.    Unfortunately (as with everything else), my answer to the question is “it depends.”   But it won’t help anybody, so, let’s go over several potential scenarios and see one of them makes sense to you. Case 1: you are expecting harvest in 2-3 weeks I think many of Chardonnay and other early white cultivars are about to be harvested.   Luckily, around Winchester area, we have had a good stretch of relatively dry weather.   We had rain showers came in several times, but only two of them, one at 8/4 and another one on 8/20 were long enough to initiate major late season diseases, such as Botrytis.   We have three Botrytis trials, but we have not seen evidence of Botrytis outbreak.   Moreover, at Winchester area, a forecast of next rain is on next Tuesday, and it looks like a case of another thundersto...

Some of our early cultivars such as Alandale is changing it color.  It is just a matter of time to see other cultivar to enter phase of veraison.  Hopefully, we will keep seeing dry weather with little bit of rain here and there.... There are several diseases to be considered at this stage.  One of them is Botrytis.  The spray timing for Botrytis is at bloom, bunch closure, and veraison.  The pathogen seems to be active throughout the season, but Botrytis likes berries when they get mature and accumulate more sugar.   As usual, canopy management is the first line of defense against grape disease management and this is particularly true for Botrytis since it tends to develop after a long period (15-17 hours) of high humidity condition. Please keep in your mind that Botrytis is very well known for its capability to overcome fungicides.  Thus, a rotation of mode of action groups is very important aspect for Botrytis management.  The ...

I have received several emails about black rot recently.  With the frequency of rains we observed so far, it is not surprising to see small amount of black rot even if you had a very good coverage of fungicide. Typically black rot starts off as brown discoloration on the berry, and associated with production of fruiting bodies which are often look like black dots (the size of ground black pepper?).  The picture above is not the best, but you see black dots on the one at the top of the picture.  Eventually, the infected berry will become hard and dry mummified berry with a lots of fruiting bodies, which you can see here and there in the picture. If you are seeing something like the picture above, chances are the infection happened at least two weeks ago when berries were susceptible to the infection by black rot pathogen (and so as by powdery mildew or downy mildew pathogen).  I can say that because it takes about 2 weeks after infection for black rot pathoge...

Looks like we have openings in the sky today and tomorrow.  What a wet year! Here's a copy of handout from the extension meeting held at Loudoun county last week .  It covers weather condition at Winchester, seasonal updates, and fungicide updates.

Since we are expecting heavy rain event on Saturday, plus about to be done with the critical time for cluster infection by downy mildew, powdery mildew, and black rot (which last 4-5 weeks after bloom), I received a several emails about the application timing.  As with other timings, it really depends on so many factors, but here's my take on it.      If you have a history of black rot and downy mildew in your vineyard, you may have a higher disease risks.  If you are in this situation, AND if you think that your previous application was waring off, then you may need to apply some protection before the rain.  However, if your previous application was within 7-day or have not seen many rains, or not having much issue with downy or black rot, then you probably do not need to panic.     A good news is that it looks like we have an opening after the Saturday's rain event.  (then a few more days of rain in the early part of the week)...

Most of us are about to see the end of critical time for berry infection by black rot, powdery mildew, and downy mildew.  Please keep up as much as you can with protection of vines for next few weeks.  I know many of us experienced some degree of flower and berry infection by either black rot or downy mildew due to frequent rain events, but once we pass the critical period (4-5 weeks after bloom for most of cultivars, and maybe 5-6 weeks for some susceptible varieties), these pathogen cannot cause disease on mature berries. The next critical spray is for Botrytis at bunch closure and veraison.  Make sure to remember about rotation of mode of actio n groups as well as tank mixing.  Since many of Botrytis specific materials are prone to have fungicide resistance issue, it is better to mix with a broad spectrum material such as captan or copper.  (Mancozeb can be used too, but we are approaching to the 66-day PHI.)  Another important IPM component for Botr...

The warm 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 critical period to prevent Botrytis, ripe rot and Bitter rot, because pathogens of these diseases can infect flower parts and come back later. We do have materials with kick-back activities against downy (Ridomil products, Phosphonates, etc.) and black rot (myclobutanil, etc.), but infection on flowers and young fruits can happen very fast.  Unless we have a very dry season, this is the time where you have to be proactive.  (Note: recent warm and humid night time conditions are favoring spore production of downy mildew pathogen)  Thus, what I recommend often is use of protectant materials to p...

I posted general "rule of thumb" about application (or re-application) earlier this season .  Dr. Annemiek Schilder at Michigan State University recently published a very nice write up about it. She answers many of questions we have in our mind, when the fungicide residues to be washed off from the rain, efficacy of spreader-stickers, and systemic fungicides.  Please check it out.

Today is the one of the days when you find many things in the vineyard!  Mealybugs (white one in the middle of the picture) are also observed, mainly at the base of the shoot (or a spur in this case).  You also see a scale insect on this picture.  Please note that both mealybugs and scale insects can transmit several virus pathogens, including the ones cause grapevine leafroll disease .   Unfortunately, once the vine is infected, only remedy is removal of the infected vine.  (However, please note that the presence of leaf roll virus does not always results in immediate loss of crop.)  If you have both mealybugs and virus infected vines, and have a plan of expansion, it is probably a good idea to protect new vines using insecticides.  However, you have to make sure you have both the virus and mealybugs to justify your action since insecticides for mealybugs are relatively expensive, and as with other chemicals, application of unnecessary insecti...

On the previous post, I mentioned that "At this time of the season, what we typically recommend is either mancozeb or captan mixed with sulfur to protect young shoots and leaves.  The reason why I typically do not recommend a use of newer materials such as Revus or Phosphite for downy or Luna or Rally for powdery is because we want to keep it for the critical time for cluster infection, which is from bloom to 4-5 weeks after bloom." However, it looks like at out site, the downy mildew pathogen is taking advantage of the weather conditions.  Although our last application of mancozeb and sulfur was only 6 days ago, I noticed that some of older leaves show symptoms of downy mildew (i.e., the infection might have happened prior to the previous application).  At this point, many of leaves look like the first picture, and disease incidence is probably less than 0.5%, thus, it is difficult to find them; however, we came across with a few leaves with clear symptoms as in t...

Winchester area received a series of rain over the weekend, and it looks like we may see more coming in the next few days.  There were three days of low and moderate Phomopsis infection risk events over the weekend.  Also, humid and warm nights can promote development of downy mildew spores.  At this time of the season, what we typically recommend is either mancozeb or captan mixed with sulfur to protect young shoots and leaves.  The reason why I typically do not recommend a use of newer materials such as Revus or Phosphite for downy or Luna or Rally for powdery is because we want to keep it for the critical time for cluster infection, which is from bloom to 4-5 weeks after bloom.  If this warm temperature continues, the bloom may comes soon, though!!

Two days of intermittent rain brought a low infection risk event for Phomopsis.  Also, these spring rain events can be precursor events for both downy and powdery mildew.  As noted in the previous posts, keep protecting young shoots from these pathogens.  At this point, you can use mancozeb, captan, and sulfur. (Note: for some reason, this post was not posted in a timely manner.  Sorry!)

As usual, we start our season with rains.  It has been more than 13hr of wetness so far at Winchester with an average temperature of low 50s.  It has accounted for a low risk of Phomopsis infection, and a line of rain just passed the area too.  We will see how it will turn out over the weekend. As shoots extend rapidly in the early part of the season, the new tissues are not protected by the previous application of fungicide(s).  Keep in your mind to protect these new tissues. I often am asked about when to reapply fungicide(s) after rain.  An often discussed rule of thumb is: < 1 inches of rain: Continue with intended spray interval 1-2 inches of rain: Consider shortening your spray interval in half.  (E.g., if there is 7 days remaining for the normal spray interval, shorten it to 3-4 days) >2 inches of rain: Consider re-application soon. However, please note that it also depends on the history of your vineyard(s), cultural practice, and a...

We will have a vineyard meeting tomorrow (sorry for a late notice...  I have been bit busy...) at Early Mountain vineyards . We will start from 11 and finish around 3.  There will be vineyard tour and seasonal updates from us.  You can either bring your own lunch or purchase it from the winery ($11 or so). Here is my handout for the meeting . See you tomorrow!

Our 6 years old  Chardonnay had 100% bud break today (4/22/2015)!  Looks our our season has officially started. There has been a few email inquiries came to my inbox about climbing cutworm.  We have applied Intrepid to "hot spot" which is a few panels facing wooded area for us.   Please refer to Doug's posting and UC IPM for more information.

Our young 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 infection on shoots and rachis.  It also causes berry infection, which is not common with wine grapes because of our spray programs.  Materials for black rot and downy mildew are often effective against Phomopsis, thus, coverages for these diseases are also working as management of Phomopsis, especially later in the spring/summer. Phomopsis tends to appear as a vineyard gets older because this disease 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, are more susceptible to Phomopsis than others.  The fungus survives in canes and trunks that were ...

2015 Integrated Pest Management (IPM) meeting announcement Virginia Cooperative Extension Specialists will review pest management considerations for a full day IPM workshop.   The morning of review will be followed by interactive pest management scheduling for the 2015 growing season. We will have only one IPM meeting this year, centrally located at King Family Vineyards in Crozet, VA on March 10, 2015.   http://www.kingfamilyvineyards.com/ The meeting will begin at 9 am and should conclude by 4 pm.   Please bring your own lunch – we plan to have discussions during lunch. What: 2015 vineyard IPM Workshop When: March 10 2015, beginning at 9am – we will finish by 16:00 Where: King Family Vineyards; Carriage House This workshop will take place indoors- bring a notepad, writing utensils, bagged lunch and a copy of your spray program from last year. There is no fee for the workshop; please confirm your participation by sending a message to Trema...

It was nice to see you all at the VVA meeting.  Here are slides of my presentations.  The links should open up files in my Google Drive (pdf files). 1) Beginner's workshop 2) Interactive Disease Management Planning 3) Winter-time disease management of trunk diseases We are currently planning an IPM workshop at Nelson county on March 10th.  If you are interested in, please keep the day open.  It will be a whole day event with a series of presentations from our experts on viticulture, insect management, weed management, and of course disease management.  I am hoping to have the interactive session again with more time to actually finish the season.  ;)

Here comes information on this year's VVA meeting! If you are new to the industry, please consider attending VA vineyards association’s annual meeting.  This year, we have a half-day beginner’s workshop on Thursday the Feb 5th Introduction to mid-Atlantic wine grape production When: 5 February 2015 Where: Omni Hotel, Charlottesville VA (part of the VVA’s winter technical meeting) Registration: At VVA website (http://www.virginiavineyardsassociation.com/) Details: This will be a team-taught program designed for those either exploring grape production or recently engaged in wine grape growing. Program will be followed by a reception with experienced grape growers and winery representatives. Virginia Vineyards Association’s winter technical meeting When: 6 -7 February 2015 Where: Omni Hotel, Charlottesville VA Registration: At VVA website (http://www.virginiavineyardsassociation.com/). The meeting is open to all, not just VVA members. The program timing details are p...