Virginia Grape Disease Updates

It finally stopped raining, but we (Winchester area) are having an on-going wet event since 10/9/13.  I counted >108 hours of wetness with an average temperature of 54F (ranging from 48F to 60F).  It has been a long enough for Botrytis, and although the temperature was bit low, downy mildew probably had some chances as well. Here is a list of things to be considered: 1) Time to harvest (if you are picking in a few days, I do not see the benefit of spraying now) 2) Current Botrytis situation in your vineyards 3) Variety (red with loose cluster ~ lower Botrytis risk) 4) Canopy management (Open fruiting zone is always helpful!) 5) Birds/insect damages (more damages, higher the Botrytis risk) 6) Fungicide effect on wine quality As I mentioned earlier this week, we had Botrytis risk event on last Monday; however, it had been dry for several weeks until that rain.  Thus, the Monday's risk might not have resulted in many infections.  On the other hand, Botryti...

Rain on this Monday resulted in 10 hours of wetness with an average temperature of 62F.  It was warm and long enough for both downy mildew and Botrytis.  Once again, downy mildew risk is for leaves only.  Risk of Botrytis depends on your variety, cluster architecture, and canopy management too.  Most of varieties still hanging are red (with some exceptions, of course), which has lower risk of Botrytis.  Also, if you have an open canopy, the risk are lower too.

Since 9/2 or so, we are observing dew events that were wet enough to make our leaf wetness sensor wet almost every night.  Since our sensors were located about the same height as the lower part of the canopy, leaves were probably wet as well.  Each events were about 6-9 hours.  Most of time, temperature was low (in 50F), but sometimes were in lower 60F.  What this condition promote can be downy mildew.  They tend to sporulate under dark condition, and since their spores can swim, these dews probably are enough for them to infect new tissues.  Due to low Brix, many people are tying to hang their berries longer this year.  Please make sure to have some protection on your foliage so that it can help maturation of berries (+ store carbohydrate for the winter!).  If you are concerned about potential effect of spray materials on wine quality, you can aim your sprayer nozzles to upper part of the canopy so that fungicides won't hit the berries.

A rain event followed by high relative humidity (+28 hours of wetness in high 60F) created disease risk event for downy mildew and Botrytis on 8/28-29.

A wetness event recorded yesterday was infection event for Botrytis and Downy mildew.  Refer to yesterday's post on spray choices.  Please make sure to alternate mode of actions to reduce the risk of fungicide resistance development.

Continuous rain and high relative humidity caused Botrytis and downy mildew infection risk events on the 14th, 17th, and 20th. At this point of the season, a phosphite (aka phosphonate or phosphorous acid) material would be the best choice for downy mildew.  You may want to mix it will captan to have added efficacy. (Note: captan has 0-day PHI, but some winemaker prefer not having captan close (~3 weeks) to the harvest.)  The other potential mixing partner would be Ranman (note PHI = 30 days), Forum (PHI=28 days), or Revus (PHI=14 days).  Ranman should have some kick-back activity, and both Forum and Revus have a protective activity. As for Botrytis, we only have protective action materials, thus, please make sure to have a good coverage on your clusters.  Moreover, please make sure to rotate mode of action since this pathogen is known to develop resistance to fungicide rapidly.

Botrytis risk has been high from 8/9 to 8/13 due to frequent rain event.  This also means that downy mildew risk is high too. (I am at a conference, so, I cannot provide detailed data.  I will update it once I am back this weekend.)

On 8/6 a wetness event (~10 h in lower 70F) was recorded at Winchester, and there was another event today (~16 h in lower 70F)... Both are risk event for Botytis and downy mildew.

There was ~27h wetness event recorded between 8/3-8/4 with temperature varying from upper 60F to lower 70F.  It was an infection event for Botrytis and downy mildew.

Between 7/31-8/1, there was several wetness hours recorded, and one of them was 16h with an average temperature of low 70F.  It was a disease risk event for downy mildew and Botrytis.

July 27-28th were very wet for us.  We recoded two long wetness events (8 hours and 22 hours), which were infection events for Botrytis, downy mildew, black rot, and Phomopsis.  In addition, we had a short rain event that were long enough to be considered as downy mildew infection event. Our major concern would be Botrytis on fruits and downy mildew on leaves.  Please make sure to have protection on clusters against Botrytis.  We do not have any fungicides that work after infection takes place.

July 24 th   Gadino Cellars and Vineyard, Bill and Aleta Gadino owners. Tour Begins:   3:00pm Topics:             §   Disease Management   – Dr. Mizuho Nita, Virginia Tech Grape Pathologist §   Insects Updates - Dr. Doug Pfeiffer, Virginia Tech Entomologist §   Viticultural Update   - Tremain Hatch, Viticulture Research/Extension Associate Location: Gadino Cellars GPS coordinates 38.69073544820042, -78.16712379455566 92 Schoolhouse Road Washington, Virginia 22747 (540)987-9292

Winchester area received a short rain event on the 21st.  It only lasted a short time, but due to that relative humidity stayed high for the whole night.  (i.e., it was a good condition for downy mildew to produce spores)  Then we received rains from about 4 PM yesterday.  It resulted in about 18 hours of wetness with an average temperature of 69F.  It was an infection risk event for downy mildew and Botrytis.   Our Chardonnay is getting close to veraison, so, we probably will think about Botrytis treatment on the next round of application. (As I noted in the previous post, even though it was also events for black rot and Phomopsis, these disease should not cause major damages on your berries at this late in the season, unless you have chronic issue with Phomopsis.)

An extensive wetness event was recorded on 7/12-13 (~30 hours) with a temperature range of upper 60F to lower 70F.  In addition, there was about 9 hours of wetness recorded in 7/14 with an average temperature of 70F.  Both were infection risk events for downy mildew and Botrytis (especially the long one in 7/12-13).  (These were infection events for black rot and Phomopsis, but berries should be resistant to black rot infection and Phomopsis is typically not active late in the season.) (Note: for some reason I was not able to upload this note on time.  Sorry!)

Boy, it's really hard to keep up with rains this year! We had about 10 hours of wetness on both 9th and 10th, and about 9 hours on the 11th (yesterday).  Average temperature were in upper 60F to lower 70F.  These were events for downy mildew, black rot, and Botrytis.  However, as I noted in the previous post, berries should be out from the critical period of infection by downy, black rot, and powdery mildew.  However, with these frequent rains, risk of Botrytis is probably high overall, especially for tight cluster varieties.

We had about 18-19 hours of wetness event in lower 70F in July 7-8th.  It was infection risk event for black rot, downy mildew, Botrytis, and Phomopsis.  At this point, most of your berries are out of critical period for downy mildew, powdery mildew and black rot infection.  Rain today looks like bring another infection events... Also, please keep in your mind about the 66-day PHI of mancozeb products.  Many of early varieties are at or near the limit at this point

We (Winchester area) received a few showers in the past 24 hours, and the longest wetness event was due to a shower passed  around 5 AM this morning.  It resulted in about 10 hours of wetness with an average temperature of upper 60F. It was an infection risk event for black rot, downy mildew, Botrytis, and Phomopsis.  In addition, we received 2-3 showers that resulted in more than 90 min of wetness ( i.e., these showers were downy mildew infection risk events). Our Chardonnay is close to bunch closure stage, thus, we applied Botrytis treatments this morning.  Bunch closure is the last opportunity for us to deliver materials inside of the clusters, especially with variety with a tight cluster, such as Chardonnay.

It looks like we are going to have another wet week... The rain on the 29th was a very short one, but it was enough to make leaves wet for about 10 hours and the average temperature was higher 60F.  It was infection event for downy, black rot, and Phomopsis.  The rain on the 30th was too short for any infection. Once again, the current condition favors development of downy mildew and black rot.  Please do not let something like the picture below happen to you!  (Downy mildew on a cluster, taken from our downy mildew trial.)

I just want to remind you about the risk of downy mildew remains high this week. Downy mildew prefer to produce spores under dark and humid conditions.  We experienced a very wet night on the 23rd (no measurable rain, but RH was 100% for 8-9 hours), and then it was followed by a thunderstorm on the 24th (yesterday).  It was a very short storm with ~90 min total wetness duration, which is a minimum time required for downy mildew infection.  In addition, the night time relative humidity have been high for last few days (>80%), and thunderstorms are in the forecast every day of this week.  Moreover, our berries are probably about one to two weeks away from becoming resistant to downy mildew infection (depends on susceptibility of variety and also when it was in bloom). Thus, please make sure to protect your berries from downy mildew as well as black rot. Picture on the top is a cluster showing downy mildew infection on the tip of a cluster.  The picture be...

Luna Experience had a 10-day REI for cane work activities ("cane tying, turning, or girdling",  for other activities, REI is 12 hours); however, it has been changed to 5 days this year.  If you have Luna Experience, and would like to take an advantage of this reduced cane-work REI, make sure to have a new label.  You can download a copy from this link. As usual, please read and follow the label! 

A storm went through our area and resulted in several wetness events.  The longest one was about 11 hours of wetness with an average temperature of 68F.  It was a disease infection event for black rot, Phomopsis, downy mildew, and Botrytis.

A series of rain event started around 9:30 AM on June 6th, and continued on until about 2AM on June 8th at Winchester.  Thus we had a wetness event for about 40 hours with an average temperature of lower 60F (~63F).  It was long and warm enough for Phomopsis, black rot, downy mildew, and Botrytis.  If you are planning for fungicide application to reduce the risk of on-going infection of downy mildew or black rot, please refer to this post , or PMG, or my workbook (PMG and workbook are listed under "Resources").  Looks like chances of rain remain high for next few days across the state. FYI: Because we have seen downy mildew in our vineyard since last week, we applied Prophyt (a phoshite material) and Ranman ( cyazofamid) yesterday morning.  A phosphite material and cyazofamid has a kick-back activity and a protective activity against downy mildew, respectively.  (Note: We did not apply a material for black rot, because it may interfere with some of...

Winchester area received a series of thunderstorms from 3:00 PM yesterday, and relative humidity remained high (>90%) until 9:00 AM this morning.  Thus we had a wetness event of 18 hours with an average temperature of 66-67F.  It was warm and long enough for Phomopsis, black rot, downy mildew, and Botrytis infection.

--> I just visited another vineyard down in the south where Norton vines were in full bloom, and when I came back, our Chardonnay vines were in trace-bloom.  As we discussed at this year’s VVA meeting, bloom is a very critical time for disease management.   Downy mildew, powdery mildew, and black rot tend to show up around this time of the season, and 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.   Management of Botrytis, ripe rot, and bitter rot at bloom time can be important because these fungi can infect flower, and come back later when berries are maturing.   As you know, development of a disease depends on so many factors such as availability of inoculum (~ disease history), past and future weather conditions, variety, canopy management, etc., thus, I will not go in to details.  However, based on the past few weeks of ...

In Winchester area, rains from May 22-23 resulted in ~19 hours of wetness with an average temperature in lower 60's. We had 5-6 hours of dry period, then another rains went through the area, starting around 5PM last night. Relative humidity remained high (>90%) until around 5AM this morning, thus it was about 12 hours of wetness. Average temperature was again in low 60F. Both were infection events for Phomopsis and black rot. A total precipitation of the last three days was about 0.7 inches. Also, in the last few days, night time temperatures were warm (in 60's) and relative humidity were high, thus, these could be downy mildew sporulation events as well.

We did not receive afternoon rains at Winchester yesterday. We were hoping for it because we are planing a new vineyard... However, we received a short rain around midnight yesterday (5/20/13). It was followed by fog, and relative humidity stayed high (>90%) for almost 9 hours with average temperature in low 60's. It was an infection event for Phomopsis and black rot.

Damages from Monday's frost event showed up a few days after.  About 5-10% of shoots (or leaves) on our Merlot vines which is located near the bottom of a hill showed symptoms.  Some are simply become necrotic, and others are showing mosaic symptoms. Also, although there were drizzles here and there, rains from this weekend were not long enough to be disease events at our location.  However, relative humidity was high (near 100%) throughout the last night.  Such a condition can promote sporulation of downy mildew.

Looks like some of us got a frost bite here and there.  I hear some people got mid-20's this morning.  It is probably too early to tell, but most of our vines seem to be OK so far.  It looks like it went just below 32 in our station, but not by much.  However, these baby vines in our nursery looked pretty frosted this morning.  We will see how it will go.  It takes about 24-48 hours for frost damage to show up, and with mild frost damages, you will see mosaic lesions.

Well, it looks like finally we have some break from rains. In Winchester area, rain started around 9AM on the 6th, and although there were a few interruptions, relative humidity stayed above 90% most of the time until around 9AM this morning (the 9th). Temperature varied from upper 40's to low 60's and most of time, it was low 50's. This rain event was long enough for Phomopsis and black rot infection events. A few people asked me "What should I do now?" Well, it depends on when you have sprayed last, and also, what type of history of black rot you had in the past. If you missed the spray before the rain (i.e., your last spray was more than 10-14 days ago), and your vineyards had an issue with black rot (which is not a common), it may be a good idea to consider either a DMI (SI) or a QoI (Strobilurins). We want to keep DMI for later use, so, unless you know for sure that the rain from the past few days will give you an issue with black rot, my recommen...

Looks like we are expecting three days with high chance of rain from Monday.  I sprayed our vines with mancozeb (3 lb/A) and sulfur (3 lb/A) yesterday. At this point of the season, my target fungal disease is Phomopsis since this pathogen can be active in relatively cool rain event, and we have relatively old vines (~23 years old) right next to our newer Chardonnay.  Mancozeb comes in handy because it also has efficacy against black rot and downy mildew.  These diseases typically develop little later in the season, but it is much easier to protect your vines from them than try to counter-act to the developing diseases.  I also added sulfur to add an insurance against powdery mildew. 

The total hours of wetness was about 18h with the average temperature at 50-56F.  It was long and warm enough for both Phomopsis and black rot.  Also, these spring rains will help powdery mildew spores (ascospores that are from winter survival) to be disseminated to the air.

I was out of town, and I did not realize it, but Winchester area received precipitations from a thunderstorm on the night of the 24th.  Since relative humidity was not high (60-70%), leaves did not stay wet for a long time.  (I could not see any measurable precipitation data from Winchester airport.  Maybe some errors of their instrument?)  Thus, there was no grape disease risk associated with the rain. Looks like we may see some rains next week.  If you have issues with Phomopsis, it may be a good idea to think about protective application of a fungicide such as a mancozeb product. Also, I uploaded an updated version of the workbook since I received some comments, including one from Dr. Anton Baudoin of our department ;) 

Here comes 2013 version of " Workbook for Developing an Effective Fungicide Spray Program for Wine Grapes in Virginia ".   Although I finished it a few weeks ago, and used in the IPM workshop, I forgot to post it in here!  As with the previous version, it may contain some errors, so, if you find any (or if you have comments and suggestions), please let me know. You can also download our Pest Management Guide and other materials, including Excel version of the template from the workbook, from the "Resources" section on the right hand side of this blog.

Both Chardonnay and Merlot are near 100% bud break as of today.  At this point, one disease to be considered is Phomopsis cane and leaf spot.  If you have a history of Phomopsis in your vineyard(s), mancozeb, or captan, or ziram will be a good choice for protection of young tissues. I have not seen much of Phomopsis in our young vineyards, so, I will skip this spray, and start my program around 5-10-inch shoot growth, targeting downy, powdery, and black rot prevention.

The two hot days we had pushed things quickly.  Our Chardonnay buds are swelling and some are even broke.  Our Merlot is bit behind, but not by much.  Cab sauvignon seems to be still tight.  Looks like the season will start very soon!  Since we saw a bit of damages, I applied climbing cutworm treatment to the area of vineyard where we historically have issues.

It looks like things are finally warming up!  We will see how it will go next week. I updated my spray guide for non-bearing grapevines.  This guide also contains basic disease information, so, if you are interested in, please check it out . My workbook for bearing vines will come very soon.  I am hoping to get it published by the end of this week.

A few people asked in about Topsin-M application for pruning wound protection against Bot canker, so, here is my old post about it .  You can also download a special label for the dormant application from the link.  (Please make sure to have it when you decided to apply Topsin-M.  As you know it is a legal requirement.)

We are seeking a postdoctoral scholar who is interested in working with biology of ripe rot pathogen.   If you are interested in, please apply through https://listings.jobs.vt.edu (posting SR0130030).

I just added Dr. Derr's presentation from the IPM meeting, please see the posting below.

Thank you for those of you attended our IPM meeting at Stone Tower Winery despite of cold weather!  Also, we really appreciate the great hospitality of Mike, Kristi, Bryan, and the Stone Tower team!  We had a really nice meeting. If you would like to have handouts (Power Point presentation), please click the following links. (Note: I added Dr. Derr's presentation on March 29th) 1) Dr. Doug Pfeiffer's Insect IPM 2) Jhalendra and Dr. Chris Bergh's Grape Root Borer study 3) Bill's VA SWAG (aka Sustainable Workbook) 4) Mizuho Nita's Fungicide Trials 5) Dr. Jeff Derr's Weed management IPM Also, it's a reminder that we have another IPM meeting in the central VA, as well as a beginner's workshop here at Winchester AREC.  I hope to see you there. What:   Integrated Pest Management (IPM) workshop in Central Virginia When:   9:30 – 4 pm, 9 April 2013 Where: Barren Ridge Vineyards, http://www.barrenridgevineyardsva.com/contact/directions/ Detai...

Please see the article in this link about the risk of 17-year cicada risks for this year.  Looks like many counties east of Blue Ridge Mountains are in high risk zone.  They lay eggs on branches (including grape canes), and young tender branches are more susceptible.  If you have a young vineyard (1-2 years old) in the high risk zone, you may want to consider to take an action to protect your vines (grow-tubes, netting, extra shoots, etc).  Please see Doug's article (about 2004 outbreak) for more details. Please consult with your local extension agents about the risk of your region.

I am in the process of updating my fungicide workbook for the upcoming season.  I have made a few changes on the template for fungicide scheduling.  Since many people want to have an Excel (or other spreadsheet) version of it.  I created a link of a template (just a form for printing) , as well as a Google Document (You can download the file from this page). You can also have an access to the template from the link on the right hand side of this blog. Also, just a reminder that we will have two IPM meetings, and one is coming up this week.  Please see this posting for more information .  

Our lab is seeking a part-time Agricultural Technician at AHS AREC in Winchester, VA .    The deadline has been extended because another lab in our station is looking for a very similar position, and we decided to coordinate our effort. Position requires knowledge (or willingness to learn) of vineyard oriented fieldwork, as well as basic laboratory skills that may include fungal culture transfer, PCR, etc.  Review of applications will begin on 1 March 2013 and will continue until position is filled. To view required and preferred qualifications, and to apply for position, complete the application online at https://listings.jobs.vt.edu/postings/38075 by 22 March 2013. Virginia Tech is an equal opportunity affirmative action institution.

A postdoctoral position is available at our lab at AHS Agricultural Research and Extension Center of the Virginia Polytechnic Institute and State University (Virginia Tech).  The job is located at Winchester, VA, which is approximately 60 miles west of Washington D.C. There are three main research projects.  Selection of the core research project will depend on the interest and strength of the candidate.  The first is a histopathology of ripe rot pathogens of grape ( Colletotrichum acutatum and C. gloeosporioides ) using light microscopy, SEM, GFP-transformed isolates, and real-time PCR.  The second is an investigation of fungicide QoI resistance level of ripe rot pathogens in VA vineyards using bioassays, PCR, and sequencing.  The third is a development of leaf wetness model using predicted temperature, relative humidity, and precipitation from NOAA’s RTMA (real-time mesoscale analysis) data. This position is initially available for two years with potential ...

Our lab is seeking a part-time Agricultural Technician at AHS AREC in Winchester, VA .   Position requires knowledge and experience with vineyard oriented fieldwork, as well as laboratory skills that includes fungal culture transfer, PCR, etc. Review of applications will begin on 1 March 2013 and will continue until position is filled. To view required and preferred qualifications, and to apply for position, complete the application online at https://listings.jobs.vt.edu/postings/38075 by 10 March 2013. Virginia Tech is an equal opportunity affirmative action institution.

--> There is a link under  "Handouts, Guidelines, and other", but here are the list of upcoming meetings that will be held in the next few months.  What:   Pruning workshop in Northern Virginia When:   1 pm – 4pm, 4 February 2013 Where: AHS Jr. AREC, near Winchester VA - http://www.arec.vaes.vt.edu/alson-h-smith/contact/index.html Details:    Join us for an informative session which will cover: pruning basics, vine balance, gathering pruning weights and guided pruning practice.  This meeting will have examples of VSP, pruning vines of different size, head training cane pruning vs. cordon training spur pruning, and training one year old vines.  Workshop will be outside rain or shine, bring a pair of pruning shears and appropriate weather gear.  Meet inside the building in the large conference room.   No fee or RSVP is required for this workshop. What: Pruning workshop in Central Virginia When:   1 pm – 4...

Thank you very much for attending this year's VVA meeting!  I really enjoyed the meeting.  We had a lot of disease talks this year, but I think it was a good reminder/refresher for all of us.  As I promised, here are our handouts from the meeting.  Please click the link to download them.  As with the last year, I think the VVA will post them at their website too. 1) Taylor's Virus Presentation 2) Mizuho's Phomopsis/Ripe Rot/Bitter Rot Presentation