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Showing posts from 2009

Meetings at Koru Farm (Sept 30th) Dinwiddie (Oct 1st) 2009

I think this will be the last meetings for the season. One is at Koru farm in Stuart, VA (Sept. 30th - TOMORROW!). Caryl and Greg Talcott has been kind enough to host and organize the meeting. If you can make it, please do. I will talk about new fungicide and other management information. The other one is at Dinwiddie, VA (Oct 1st). Although this is titled late season meeting, I will talk mainly about "early" season disease management for next season, since most of people are probably either harvested, or harvesting their grapes. The list of speakers (at Dinwiddie): Dr. Mizuho Nita, VCE Grape Pathologist from Winchester VA , Mizuho will be cover Early Season Management of Grape Diseases. Dr. Paul Semtner, VCE Entomologist form Blackstone VA , Paul will cover Early Season Insect Control Methods. Janet Spencer, VCE SE Area Vegetable Extension Agent in Suffolk VA , Janet will cover General Production Tips Mike Parrish, VCE Extension Agent, Dinw

Late season management topics

I've been in and out of my office with my leaf roll survey project, and it has been bit difficult to frequently update the blog. Also, at this point, not much you can do about major fungal diseases. The critical time of infection is gone. If you see downy, powdery, or black rot on your bunches, the infection probably took weeks ago, if it was not a month. Thus, I will point some key issues at this time of the year. Botrytis, downy, and other rot We had a long period of wet and cool nights during the last half of August. This conditions favors both Botrytis and Downy mildew sporulation, and potential infection on nearby leaves. (i.e., it won't spready quicky, but it probably enough to increase number of spores.) If it is followed by rain (like we had last week), the risks of Botrytis and downy mildew increase. As I mentioned earlier, downy mildew won't touch berries at this point. Berries are resistant to the infection. However, with a prolonged rain or high hu

Finally rain has come...

We had fairly dry month so far and grasses are start to getting brown, but a thunderstorm dropped about 0.5 inch of rain last Friday around Winchester area. It stared little after 5:30 pm then continued for two hours or so. The relative humidity was high until next morning (10:30 am) with an average temperature of around 70F. This accounted for infection event for Phomopsis and Botrytis on berries and Downy mildew on leaf. I listed Phomopsis here simply because it can infect berries at any time; however, often time infection around this time is not common. It is probably due to less inoculum (this fungus mainly creates the fruiting body in the spring), and it favors cooler climate. Thus, your risk depends on how chronically you have Phomopsis in your vineyards. If Phomopsis appears year after year, then your risk is higher. If you just see them only when we have a wet spring as we did this year, you probably have less risk. As for downy mildew, I started to see foliar sympt

It was a very nice workshop!

(A graft union infected by fungal organism(s)) We had a very nice workshop this Monday. Now everybody become experts of various trunk diseases! As Philippe discussed, most of fungal pathogens that cause trunk diseases often requires a point of entry. In addition to pruning wounds, accidents with a weed-whacker, etc that were in the discussion, due to cold temperature during winter, some of varieties are more susceptible to have cold injury which also can serve as a point of entry for microorganisms. Site and variety selection can play a big role in prevention of these diseases. As for other diseases we face, we had several nights with high relative humidity (8/14-16) which favors downy mildew sporulation. Then we had thunderstorm passed by on 17th and 18th. Thus, if you had visible downy mildew colonies on your leaves, the risk of new infection was high during these thunderstorms. (I'm talking about leaf infection, not berries.) At Winchester, last night's thunderstor

See you on Monday at Jefferson vineyards

We will have Virginia Vineyards Association's summer technical meeting at Jefferson vineyards on August 17th (this Monday). Dr. Philippe Rolshausen and Lucie Morton will be talking about trunk diseases. I will be there to provide some help and learn more about trunk diseases. If you would like to talk to me about other diseases or discuss about your spray programs, please let me know.

I'm back!!

Hi all, I'm back from the meeting. It was a meeting for plant pathologists, and it was a very good meeting for me to meet new people (since I'm a new kid on the block and all), as well as my other colleagues. I visited Washington's Yakima Valley grape growing area after the meeting to visit a collaborator on grape leaf roll disease project. There are very exciting area to study, and I will talk about it more in detail within a few days. The picture was taken from their field and showing mealybug infestation. In anyway, I took a quick look at what happened (weather-wise) during my trip. It seems like there are very short rains on 7/31, 8/1, and 8/5, and these were not so significant in terms of major fungal disease infection. We had 4.5 hour of wetness on 8/2 which probably accounted for downy mildew infection (primary on leaves, at this point), and 9.5 hours of wetness on 8/6, which probably accounted for downy mildew and Botrytis (and maybe black rot, if your berr

I'll be out of office until 8/11

I'm at a conference until 8/11. In the mean time, we will have a vineyard meeting at Winchester AREC on 8/5. I cannot attend, of course, but I prepared a note (click here to view) and Tony will go over it. Since I may not able to update this blog, I summarized the disease risk at this point. I hope it will be helpful. Disease risks at this point (early August) The critical period for black rot, powdery mildew, and downy mildew fruit infection should be over (4-5 weeks after bloom). Black Rot: Berries should not susceptible any longer. For the next year, make sure to remove all berries from your trellis at or after harvest. These infected berries can produce spores all season long if they are left on the trellis Phomopsis: Berries are susceptible all the time. Since we had such a long period of rain in the spring, you may see some berry infections. Usually, the damage done by Phomopsis is not significant, but if you have reasons to be afraid of Phomopsis, captan can be applie

Rains in the forecast

It seems that we have more rains on the horizon. I hope you had a chance to protect your vines, it it was not done recently. At Winchester area, yesterday's rain events were sporadic and it was not significant disease event except for downy mildew, but some of nearby area probably had more continuous rains, thus you need to check your local weather. We have having 13 consecutive nights that favors downy mildew sporulation, thus even though the threat on fruits are gone, you may want to consider downy mildew materials to protect your foliages.

Many thunderstorms...

We had a series of thunderstorms passed by the area. In terms of the duration of rain, all are short; however, it was wet afterwards because many of these rains happened after 5pm and the relative humidity stayed high until following morning. On 25th, we had rain started from 9:40 pm and RH was high until 10:00 am next morning (>12 h of wetness). On 26th, the strong thunderstorms passed starting 5:00 pm, and RH was high until 8:00 am this morning (>15 h of wetness). Average temperature during these events were mid-60F, thus, infection of downy mildew, black rot, Phomopsis, and Botrytis could happen. But as I mentioned several times here, if you passed the critical period (4-5 weeks after bloom), your berries should be resistant to downy mildew and black rot infections. Since we had such a strong wind with the thunderstorms, some of you may have experienced damages on berries (and/or even shoots and trunks). Hopefully they will dried out, but these wounds can be a course

Rain after rain....

We had a series of thunder storms on Wednesday and last night. The condition of air were dry to begin with, so, the relative humidity did not stay high after the rains (stayed in 70% range). Thus, these rains probably did not account for disease event at Winchester; however, your vineyard might had more rain or longer rain. Please check your local weather . Also, we are still having 7 consecutive nights with conditions for downy mildew sporulation. Even with a short rain (>90 min), it can cause an infection, thus, if your berries are still in a critical time (4-5 weeks after bloom), and you see leaves with downy mildew in your vineyards, then you may need to react to these series of infection event with Phosphorus acid or Ridomil products. However, if your berries passed the critical time, the risk of infection is very low. Once again, the fungus you may need to concern at this point is Botrytis. Make sure to protect your bunches with Botrytis materials (please read previo

More rains in the forecast

Rain on this Monday did not last long, but since it started later in the day, the relative humidity was high (>90%) until next morning. Thus, we had >15 hours of wetness event with an average temperature of 68F or so. This accounts for infection event for Phomopsis, downy mildew, black rot, and Botrytis, and ascospore discharge for powdery mildew. And I'm aware that areas in the south of us received more rain last night. Please check your local weather record . In addition, we are having five consecutive nights with high relative humidity that favors downy mildew sporulation. If you have issues with downy mildew this year, you may need to take some action before or after next round of rain. ( but again, it depends on growth stage of your berries. If it is past 4-5 weeks after bloom, the risk of downy mildew infection on berries is very low. ) Unfortunately, there is no curative fungicide for Botrytis, thus you need to protect your berries against infection. As I me

Two wetness events recorded on Friday

We had two wetness event due to lines of rain passed by yesterday (7/17/09). The first one started around 11:30 am, and wetness lasted until 3:30 pm or so (4 hours) with an average temperature of 71F. The second one started around 8:40 pm and wetness lasted until 2:00 am (6 hours) with an average temperature of 66F. These events accounted for downy mildew infection, potential powdery mildew ascospore discharge, and light infection for Botrytis. Both are little shy for black rot infection event. As I mentioned in the previous post, your vines should be very close to the end of the critical period. After it is done, you can relax a bit in terms of downy, powdery, and black rot infection on berries. More rain events are in the forecast on Monday to Wednesday.

Rains in the forecast, and a vineyard meeting at Pollak Vineyards

There is a vineyard meeting tomorrow at Pollak Vineyards from 11 am. I won't be there, but here is my handout for tomorrow , which talks about risks of diseases at this point and a disease update at Winchester. Tony will be there to discuss about viticulture topics. There are chances of rain in next few days in the forecast. However, so far, we haven't had a night which favors downy mildew sporulation for a while. In addition, your berries should be developing resistance to downy mildew and powdery mildew at this point (4-5 weeks after bloom). For black rot, it may take little longer (up to 8 weeks after bloom, depends on variety), thus, please scout your vineyards for black rot. Black rot fungus takes about 2 weeks from infection to sporulation. Thus, you do not see it right now, your risk is low because there is not enough time to have an outbreak. If you have some degree of infections on berries and leaves at this point, and if you are concerned, Rally (myclobutan

Another dry weekend :)

We haven't experienced major disease event for a while. On 7/9-7/10/09, we had two consecutive nights that were favorable for downy mildew sporulation, and on 7/11/09, there was a short thunderstorm (~ 1 hr, 75F, 0.42 inches). It dried up quickly, thus, it may or may not be long enough for downy mildew infection (~ 90 min is required). For some location, it might been an infection event, so, please check your local weather record. Most of your vines are getting close to the end of the critical period (bloom to 4-5 weeks after bloom) for berry infection by powdery mildew, downy mildew, and black rot. After this period, you can relax a bit. The next disease to be considered is probably Botrytis. There is no formal study done yet, but many growers experienced that if you apply fungicide before bunch close and varison, the risk of Botrytis outbreak decreases. I think the logic behind it is that the application before bunch close provide a good spray coverage for both outside

No, it's not chocolate truffle...

On Sunday and Monday morning (7/6 and 7/7/09), we had relatively high relative humidity (>80%) at night which favor downy mildew sporulation. Thus, if downy is your concern, you may want to scout your vineyard. (But remember that it requires rain for new infection.) As I mentioned several times, we have an experimental plot where some of vines are not treated with any fungicides. On these vines, black rot, powdery mildew, and downy mildew become very severe. Last time I showed black rot, so, now it's a turn of powdery mildew. Powdery mildew on upper leaf surface Powdery mildew on bunches... No, it's not truffle... Powdery mildew on a cane

It was a nice and dry weekend

I hope all of you had a nice 4th of July weekend. I'm glad that we did not see the forecasted thunderstorm events. Most of vines should be approaching the end of the critical period for powdery mildew, downy mildew, and black rot infection on berries. Berries of V. vinifera varieties become resistant to infection after 4-5 weeks after bloom. ( V. labrusca vines become resistant after 2-3 weeks, hybrid varies.) These pathogens still can infect, but the success rate declines rapidly after this period. In Winchester, >50% bloom was observed on Chardonnay on 6/6/09 and on Cabernet sauvignon on 6/9/09; thus we have about a week to 10 days to go. After this critical period, weather condition in VA typically becomes unfavorable for downy mildew and black rot (hot and dry), and powdery mildew control becomes a key issue. Please scout your vineyards for diseases and adjust your spray schedule accordingly. Also, this is about the time Japanese beetle becomes an issue. I'

Happy 4th!

The thunderstorm on 7/01/09 lasted a little over an hour (0.73 inches); however, RH remained high for about 9 hours with an average temperature of 65F. Thus the event was long and warm enough for Phomopsis, downy mildew, and black rot infection, and powdery mildew ascospore discharge. Also, we had nights with relatively high RH (>80%) in 6/29 and 7/2. If these are isolated events, you do not need to worry about; however, as we know, the early part of June was very wet and we had many nights with a favorable condition for downy mildew sporulation. Sure enough, when I checked vines yesterday, we had a lot of sporulations under side of leaves. If you have seen these spores on many of your leaves, you may want to think about protecting healthy leaves and berries from next infection event, or use materials with a curative activity (Phosphorus acid, Ridomil etc). The other disease I found quite a bit in our untreated vines are black rot. This is one of diseases which you really ne

Thunderstorm is coming...

The radar is showing thunderstorms for tonight (now I heard the thunder...); however, in the past few days, there is only one night when the condition was favorable for downy mildew sporulation. Since we are approaching the end of critical period, those of you who has not seen much downy mildew can relax a bit once the 4-5 week window has past. If you are concerned about downy mildew based on your assessment of the vineyard and if the vines are not protected, then you can apply Phosphorus acid or Ridomil products after the rain. (The forecast is showing chances of rains coming later in this week.) We visited a vineyard at Southern Piedmont AREC yesterday. This vineyard is set to test a relatively low input practice (14-day schedule of mancozeb+sulfur is the backbone). This year, they did not experience extensive rains as Northern part. In addition, they managed the canopy very well. As the result, we could not find major outbreak of disease. It tells you that the importance o

So far so good.

We had a short thunderstorm event on Friday (26th), but it lasted about 3.5 hours with an average temperature of 73F and a total precipitation of 0.33 inches. It was sufficient for powdery mildew ascospore discharge, and downy mildew infection. We are expecting see some more thunderstorm later this evening. As I mentioned in the previous post, most of us are still in 4-5 weeks after bloom which is a critical period for berry infection by black rot, powdery mildew, and downy mildew . I'm not advocating excessive application of fungicide here, but just reminding you that this is the critical time. If you have already protected your berries, you do not need to be panic. So what will happen when you failed to protect your berries? Here are some examples from unsprayed vines in my plot. Powdery mildew on berries Black rot on berries Black rot and powdery mildew on berries...

Thank you for your attendance.

Thank you very much for attending the vineyard meeting at Doukenie last night. If you could not make it, you can download my note from here . As I mentioned several times in here and in this note, time period between bloom to 4-5 weeks after is the critical time to protect berries from downy mildew, powdery mildew, and black rot for most of wine grapes ( V. vinifera varieties) . Please scout your vineyards and make an adjustment to your spray schedule, if needed. There are some chance of rain tomorrow and on Sunday. The average relative humidity was low (~50%) and average temperature was around 71F last night. Now we have five nights without favorable conditions for downy mildew spore production; however, we had so many nights with favorable conditions for spore production during early June, so, keep that in your mind. Also, in our untreated vines, I start to see more and more powdery mildew. Rain events in last month or so probably provided enough opportunities for powdery

Grape root worm + vineyard meeting at Doukenie Vineyard

We found infestation on new vines by these bugs. For more information, please refer to these extension factsheets from Virginia Tech and Cornell University . Damage on leaves (adults feed on leaves) (White spots are residues from fungicides) Culprit: adult grape root worm We had an another night with low RH (in 70% range). Hopefully this trend continues! Plus, we have a vineyard meeting this evening (6 pm) at Doukenie Vineyard . I hope you can make it.

Nice weather so far!

This may be the first time in a long time that I don't mention about disease risk ;) We had two nights with relatively low RH which makes less conducive for downy mildew sporulation. But remember that we had more than a week long favorable weather for downy mildew. These spores are still out there. Hopefully we do not receive major rain events in the near future. Our Chardonnay was about 50% pea-size and Cabernet sauvignon was about 100% BB. They are moving fast!!

I'm back!

Finally, almost a week long meeting is done and I'm back in Winchester. Here's a summary of what happened during last week. 6/15 : night time temperature ~64F, RH 7-80% (DM) 6/16 : night time temperature ~68F, RH 9-100% (DM) 6/17 : night time temperature ~65F, RH 7-80% (DM), plus, rain events from 3:40 am followed by high RH until 3:40 pm (~12 hr), average temperature was about 67F, a total precipitation was 0.64 in: (Phomopsis, Powdery mildew, Downy mildew, Black rot events) 6/18 : Rain events from 12:20 am followed by high RH until 6:40 am (~ 6 hr), average temperature was about 60F, a total precipitation was 0.22 in: (Phomopsis, Powdery mildew, Downy mildew, Black rot events) 6/19: night time temperature ~65F, RH 90% (DM) 6/17 : night time temperature ~70F, RH 90% (DM), plus, rain events from 8:40 am followed by high RH until 11:40 pm (~3 hr), average temperature was about 73F, a total precipitation was 0.53 in: (Downy mildew infection event). There were several

Finally, a nice weekend!

Since the last posting, we had showers on early morning of 6/13/09, but it was not significant in terms of duration of potential wetness event. Night time temperature has been consistently in upper 60F and the relative humidity is ranging from 70-90%. With combination of 10 conducive nights we had, I assume that we still have good conditions for downy mildew fungus to produce spores. I'll be out of my office due to a meeting until Friday. I should be able to check emails and probably update this blog, but it may depends on how busy I get at the meeting (no, it's not one of fun meetings...).

Downy mildew gallery

At Winchester, we had light rain events during the night of 6/12/09, but it was short events and the relative humidity was low (80% or so), thus it probably did not promote any infections. However, we are experiencing continuing favorable nights for downy mildew sporulation (average T>55F, high RH (80-100%)) for 10 days now. Yesterday, we conducted a formal disease assessment, and observed first incidence of powdery mildew for this season. We had plenty of infection events in last two months, so it was not surprising. At this point, it is a trace level of infection on untreated vines. Downy mildew was the major disease so far. We had up to 40% incidence on untreated vines. Next runner-up was black rot. It varies vine to vine, but some of vine had 10-15% incidence. Phomopsis was omnipresent as I expected from early May rain falls, but severity was low overall. We will examine diseases again in the near future, and I will update as the season goes. Here is downy mildew ga

Another thunderstrom...

We had a thunderstorm went through the town yesterday evening around 5:40 pm then there were several rain events throughout the night (~0.48 inches). The relative humidity is still above 90% as of 8:30 am (>15 hours) and average temperature during this wet event is about 65F. As you might guessed, it was an event for Phopmopsis, black rot, downy mildew, and Botrytis infection, and powdery mildew ascospore discharge. Also, we are having 8 consecutive nights with temperature in mid-60F and RH being high (90-100%, except on 6/8/09, but it was still in 80% range). This warm humid nights promotes downy mildew fungus to produce spores. We are expecting more rains to come in next few days. We'll see...


At Winchester, we had a series of thunderstorms went through the area from 3:30 to 6:00 am or so (0.47 inches). The relative humidity was above 90% until around 7:30 am. Thus, it was about 5 hours of wetness with average temperature of 68-69F. It was an infection event for Phomopsis (light infection) and downy mildew. In addition, warm temperature and high RH probably promoted downy mildew to produce spores. As I type in this post, the sky is getting darker... I guess we will have another thunderstorm this evening.

It was nice and warm weekend, but...

At Winchester, we had four nights (6/4-6/7/09) with average temperature above 55F and average relative humidity in 90% or more. During last night, average temperature was about 69F, and average relative humidity was little low, but still around 80% range. These warm humid nights favor downy mildew fungus to produce spores. With rain events in weather forecast, downy mildew would be a major concern as I noted in the previous post. Please review your vineyard situations (as I went through in the previous post), and be prepared. Hopefully, rain does not hit us as in forecast, but you never know.

Finally, a dry weekend!

Thank you for those of you who made to the meeting at White Hall. My handout can be downloaded from the previous post. The rain is gone for now, and in the last three days, we had about 1.2 inches of rain, and wetness event lasted over 68 hours with average temperature of 58F. As you can imagine, it was good for Phomopsis, black rot, and downy mildew infection, and powdery mildew ascospore discharge. In addition, we had three consecutive nights with temperature above 55F which promote downy mildew sporulation. We are expecting even more rains next week. If you are in the same situation, please be prepared. Depends on when you applied the last application, what chemical you applied, how much rain you received, which variety you have, and the history of your vineyard, the situation will be different. However, it is blooming-postblooming time when the all major fungal disease can cause damages to your vines. I'm not an advocate of the intensive management, but these series

Rain, rain...

It rained from 11 am yesterday at Winchester, and the rest of the day was wet (0.18 inches). It accounted for at least 13 hours of wetness (+ continuing today) with a mean temperature of 58F. As you can imagine, even though the temperature was low, it was long enough for Phomopsis, black rot, downy mildew infection, and powdery mildew ascospore discharge. We'll have a meeting at White Hall vineyards today(6/5/09) from 11 am. I'll talk about biology of major fungal diseases for VA wine grape using Powerpoint. The contents will be similar to the other talks, but you get to see more pictures. ;) Tony will be there to talk about seasonal update as well.

Thank you for your attendance.

Thank you for those of you who made to the meeting. If you missed it, you can download my note from the previous post. We had a thunderstorm last night and it rained from 7:20 to 8:20 pm. The relative humidity was above 90% for 5 hours or so afterwards, and temperature was in mid-60F. Then temperature went down to upper-50F, and as a consequence, the RH went up. It was a windy condition, so, I'm not sure leaves were wet the whole time, but if it was, it was about 12 hours of total leaf wetness with temperature ranging from 68-55F. It was good for Phomopsis, black rot, downy mildew infection, and powdery mildew ascospore production. (note: If leaves dried out after 5 hours or so, then it was good for light infection for Phomopsis, downy mildew infection, and powdery mildew ascospore production.) We are expecting more rain events today, but temperature seems to be low (mid-50F). Hopefully, it will be low enough so that downy mildew won't be too happy.

Vineyard meeting at Linden tomorrow from 11 am

As Tony mentioned in his email, we will have a series of vineyard meetings this week. The first one is tomorrow at Linden vineyards , starting from 11 am. I'll talk about early season disease management, similar to what I presented in previous meetings, but I added a section for Botrytis. You can download the note from here . Tony's student Mr. Tremain Hatch will talk about nutrition management, and Dr. Chris Bergh from our station will talk about grape berry moth research. The next meeting will be held at White Hall vineyards on this Friday (6/5/09) from 11 am. I'll talk about biology of major fungal diseases for VA wine grape using Powerpoint. The contents will be similar to the other talks, but you get to see more pictures. ;) Tony will be there to talk about seasonal update as well.

Started blooming!

Our Chardonnay started to bloom yesterday. It was about 0-10% blooming yesterday and now it is about 15-50% per vine (variability among vines), and each cluster is about 10-50% open. Cabernet sauvignon are still holding tight.

Rained again. :(

Last night, we had several rain events which accounted for about 5 hours of wetness. Average temperature during that period was about 60F, and total amount of precipitation was 0.17 inches. It could be a light infection event for Phomopsis, powdery mildew ascospore discharge, and downy mildew infection. (little too short for black rot infection) I went back to the vineyard and took a look at the leaf lesions I showed here on Friday. Sure enough, there are sprangiophores (a tree-like structure containing spores) coming up from the underside of the leaf. As I mentioned in Friday's entry, it takes 1-2 weeks to develop spraongiophore, thus, the infection probably took place during 5/16-17 rains (I wrote 17-18th, but it was 16-17th). We are expecting few more chances of rains during this week. If your vines are close to bloom or blooming, please be ready to protect your vines.


Yesterday, thunderstorms passed by Frederick county from around 4 pm to 5pm. There were other rain events afterwards, and the relative humidity was high until 7:30 am or so. It accounted for >15 hours of wetness event with average temperature of 68F or so. Total amount of precipitation was 0.47 inches. It was warm and long enough for Phomopsis infection, powdery mildew ascospore discharge, black rot infection, and downy mildew infection. Also, now we are having 5 consecutive nights with temperature above 55F with the relative humidity in 80-100% range which can promote downy mildew sporulation. Speaking of downy mildew, I started to see potential downy mildew lesions on some of our untreated vines. Typically, after infection, "oily spot" will show up on the upper surface of a leaf, then you will see "downy" fungal body on the underside of the leaf. This downy fungal body mainly consists of many sporangiophores which look like a tree of sporangium. Spo

Still wet...

In the past few days, we had about 2 inches of rain at Winchester, but I heard that there were up to 5 inches rains observed in some places. Since the afternoon of May 25th, we have been having either rain or high relative humidity conditions continuously (RH is still above 90% as of 10:30pm 5/28/09, thus potentially, we have > 60h of wetness). Average temperature during this period was 67F in 25th, and 60F in 26th and 27th. These conditions are good enough for Phomopsis infection, powdery mildew ascospore discharge, black rot infection, and downy mildew spore production and infection. If your vines are very close to bloom or blooming, it is the critical timing for many of these disease development. As I mentioned earlier, there are some fungicides you can use after infection events. For powdery mildew, you can use any of fungicides you typically use (even sulfur) because the fungus grow on grape tissue superficially. For black rot, Rally (mycrobutanil) has a good curative

Now it's raining...

It looks like we will have a rainy week. Since Saturday, we had three nights with average temperature above 65F with the relative humidity in 80% or more at Winchester. These warm humid nights are favored by downy mildew sporulation from infected leaves. And these series rain events will help them to infect leaves, rachis, and berries. Thus, it is possible that downy mildew had a chance to produce spores during these nights, and these spores are ready for infecting grape tissues. Therefore, for the next round of application, you may want to think about adding a fungicide for downy mildew with curative activity such as Ridomil products. But once again, the risk of diseaes development depends on the history of your vineyard and other environmental conditions such as variety, traning system, etc. If downy mildew has not been a problem in the past, the risk may be less.

No significant rain so far!

There was a sprinkle in the morning, but so far, we haven't experienced a significant rain event yet at Winchester. Our Chardonnay and Cabernet sauvignon have been moving its growth stage. It was about 8-90% with 8-9 leaves unfolded with elongation of rachis (E-L 15) for Chardonnay, and about 3-50% E-L 15 for Cabernet sauvignon. Cab sauvignon has more variation among vines, which is consistent since bud break. I start to see development of black rot lesions on untreated vines. It takes 2-3 weeks to develop fruiting bodies (black specks within tan colored lesion), thus, rain events during 5/5-5/7 or 5/11 are probably responsible for the infection. I hope you do not see many of these symptoms in your vineyard. If so, you need to protect your berries very well so that it won't affect your yield. Mancozeb, captan, and azoxystrobin (Abound) works well as a protective fungicide application, mycrobutanyl (Rally) works well as a curative fungicide, but I doubt that it will kil

Rain forcast on next few days.

(Today's picture is our friend Phomopsis again! Left side has more spots probably because it is closer to the vine where the fungus survives and produce spores. Spores were rain splashed to the leaf to cause infection.) It seems that pretty much all over Virginia is expecting some type of rain during next few days. I do not know how "30-40% chance of thunderstorm" turns out, but if your last spray was more than two weeks ago and/or your vines have grown a lot from the last application, then you may need to be prepared for these chances of rains. As I noted yesterday, please adjust your spray materials and spray amount based on your vine's growth stage.

Thank you for your attendance.

I appreciate those of you who showed up at the meeting. I'll try to visit the meeting in the other regions as much as possible. [I do have a research to do, so, I cannot go to every single one of them, though. ;)] It looks like we will have good weather during next few days, and I think most of you are thinking about pre-bloom or at-bloom applications right now. (Those of you in the Southern VA may be thinking about 1st application after bloom.) Temperature is getting higher (although we had 3-4 days of cool nights), and many of common disease organisms are more active around 60-75F. At pre-bloom, you need to think about Phomopsis, powdery mildew, black rot, and downy mildew control, and for at-bloom or the first application after bloom, you need to add something for Botrytis control. Pre-bloom to 2-3 sprays post-bloom are very critical sprays for disease control in VA growing area. Rachis and flower part can be infected by these fungi and results in direct problems, and

Central VA vineyard meeting at Lovingston tomorrow

A vineyard meeting will be held at Nelson extension center (just south of Food Lion on Thomas nelson Highway (Hwy 29)) at Lovingston from 11 am. I'll be talking about the same early season disease management information I presented at the previous meeting . The temperature in the morning did not go down enough to cause damage on our vines. I hope your vines are OK as well. These two nights are too cold for disease development. Our Chardonnay was ~90% 7~8 leaves unfolded (I have not observed rachis elongation yet), and Cabernet sauvignon was about 8-90 % 7~8 leaves unfolded. I'll probably apply pre-bloom applications in the near future.

Another frost advisory tomorrow morning (5/19/09)

Our low was low 40's this morning. It suppose to be warmer tomorrow and I hope that we do not get any frost damage. We'll see. We received several disease samples today which I'd like to share with you. The first one is crown gall. This is caused by a bacterium called Agrobacterium vitis . This gall formation is due to genetic modification caused by the bacterium to the infected grape vine. Sometimes it is only a cosmetic damage, but the gall tissue could girdle the vine and restrict the movements of water and nutrients, then results in the death of the vine. There are some chemicals and biological agent available against gall formation and prevention of the disease, but as far as I know, none of them are very effective as you would expect from other chemical treatments such as fungicides. Removal of the infected vine and then replacing with a certified vine is the common method of management. However, you need to keep in your mind that this bacterium can survive i

Frost Advisory tomorrow morning.

As you may noticed, temperature has been declining since this morning. National weather service is issuing frost advisory from 4 to 9 am tomorrow (Monday) morning for Frederick county. Please check your local weather. Recent series of rain events are providing enough moisture to vines to push their shoots rapidly, and these succulent tissues are sensitive to stresses. If you are the lucky one with one of air circulation systems (propeller etc), this may be the time to use it. Hopefully, your vines won't experience frost damages. Our Chardonnay was about 80% 7-8 leaves unfolded (~10-inch or longer), and Cabernet sauvignon was about 20% 7-8 leaves unfolded (7~10-inch) as of today. (Phomopsis symptoms on a vine in our experimental vineyard, 5/17/09) As for disease concerns, we experienced rains and thunderstorms yesterday from 6:20 pm to 10 pm, then there are light rains here and there until 2 am or so. The relative humidity was above 90% until 3:20 am. Temperature started of

A wet night and more rains to come

It turned out to be a very nice day for planting at Winchester. We almost finished planting of two vineyards (a total of 1/2 Acre with Chardonnay and Merlot) which will be used for chemical trials and other management-related experiments. We had a drizzle in the early morning, but the expected thunderstorm did not arrive until 8pm or so and it was not as severe as I expected. On 14th, night time relative humidity was high, but temperature was low (low 40's), thus it was not a disease night. But last night, we had a series of short rains and temperature stayed in low-60's with the relative humidity above 90% until now (8am, fog). This >12 hours of wetness accounts for Phomopsis, black rot, powdery mildew, and downy mildew infection events. We are expecting to see more rains during this weekend, so, please think about potential disease events (in the future or in the past) when you decide for a fungicide application. You can find details of infection events I'm d

Thank you for those of you showed up at the vineyard meeting

Thank you for those of you showed up at the vineyard meeting, and we thank Jeff to host the meeting. The notes I used at the meeting can be downloaded from here . Last night was another cool night around Winchester. The relative humidity was high (~90%), but average temperature was 48F or so, and it was little too cold for downy mildew sporulation. We are expecting some thunderstorms passing by during next few weeks, and temperature is expected to be in 70's. Depends on when your last application was made and how much new growth you have observed, you may need to protect new growth against this series of rains. I'll be planting my vines tomorrow. I hope I won't be rained out...

We have a vineyard meeting tomorrow at Glenn Manor

We are having nice sunny days! Some of shoots in our Chardonnay elongated to 10-inch or so (start to passing E-L 12 stage). And Cabernet sauvignon is catching up with Chardonnay. About 7-80% of shoots are 5~7-inches (E-L 12). A day before (5/11/09), we had fairly dry (~50% RH) night. We had a shower (0.03 in) in the yesterday evening (5/12/09). It lasted only 40 min or so and the RH did not stay high, thus it probably was not enough for any disease event. The night time RH was high (nearly 100%), but temperature was in mid-40s. Thus, it was not good for downy mildew spore production either. We will have a vineyard meeting at Glenn Manor vineyard and winery from 11 am tomorrow. I'll talk about early season disease management tips as I did last time, and this time it includes information on downy mildew. If you cannot make it, you can download my notes from here .

Nice weekend weather!

It has been a very sunny weekend in 70's. I can take this anytime. Last night, RH was 4-50% and temperature was around 64F. I think it was little too dry for downy mildew to be happy. Speaking of disease, I found some leaves and canes showing an initial symptom development of Phomopsis today. We have untreated vines for disease observations, and I'm hoping that these vines will provide us nice cases of diseases throughout the season. The hard-to-see dark spots with yellow hallo are from Phomopsis infection on leaf. If you take a look at shoots, what you see is: Small necrotic spots (around the center) which can be expand later in the season. Dr. Mike Ellis' group at the Ohio State is currently working on the infection process of this fungus. Based on observations on the production of the fruiting structure in my previous experiments, it looks like this fungus can spread underneath the epidermal tissue even if we do not see clear symptoms. At which point the sp

No rain, so far...

At Winchester, we did not experience the forecasted rain event yesterday (5/08/09). It was a light shower in this morning with trace amount of precipitation. One thing I noticed was the night time temperature. It was above 68F with relatively high relative humidity (mostly in 8-90% range). Under this condition, downy mildew fungus (it's not technically a fungus, but I call it fungus for convenience) can produce a structure called sporangiophore which is basically a tree of sporangia which contains spores called zoospores. Typically, we consider the risk of spore production is high when there are more than 3 consecutive nights with temperature above 55F with high RH. Night time temperature in last few days are (5/6/09: lower 50's, 5/7/09: lower 60's, 5/8/09: lower 50's, and 5/9/09: upper 60's), and you know the RH was high. The first potential infection event was on 5/4/09 around Winchester, and it takes 7 days (depends on temperature) to produce spores. Eve

Finally, the sun is out!!

As you probably noticed, the sun is out! And grape vines are moving fast. Our Chardonnay and Cabernet sauvignon has moved quite a bit as well. About 7-90% are 5-7 inches (E-L 12) and about 5-70% are 5 inches (E-L 12) for Chardonnay and Cab sauvignon, respectively. Yesterday (5/07/09), Winchester area had a brief shower (0.12 inches) from 10:25am (64.4F) to 12:00pm (64.4F), and the RH was >90% until 1:00pm. And then a very short thunderstorm from 3:40 to 4:00pm (69.8F). The first event was bit short for Phomopsis and black rot infection events; however, it was probably enough for powdery mildew ascospore discharge and downy mildew infection event. A mild temperature range favors both mildew pathogens too. Some of varieties are probably getting closer to the bloom, and you need to start thinking about these mildews. 2-3 weeks pre-bloom is the start of critical period for downy mildew rachis and berry infection. Make sure that your spray program has something against downy
At Winchester, yesterday's (5/6/09) rain started from 5pm (60.8F) and ended at 6:40pm (59.0F); however, the RH was >90% until this morning (8:40am). A total amount of precipitation was 0.05 in. Thus, it probably accounted for >14h of wetness with upper 50's in temperature (F). It would be enough for Phomopsis, powdery mildew ascospore discharge, black rot, and downy mildew infection. (I feel like I'm repeating myself...) Please do not get overwhelmed by my report of infection events. I'm just giving you the information about what could happen based on weather conditions observed. If you applied your protective fungicide application, it should stop infection. In addition, there are chemicals with curative (or kick-back) activity against powdery mildew, downy mildew, and black rot. Moreover, the risk of infection by these fungi depends on the history of your vineyard too. For example, if you had a history of outbreak of downy mildew year after year, you t

Growth stage as of 5/06/09

Plenty of water affected growth too. About 10% of Chardonnay were 5-7 inches (E-L 12). Growth of Cabernet sauvignon was not as dramatic as that of Chardonnay. As with yesterday, 6-70% of shoots are 3-inch (E-L 9) and others are 1-2 inches.

I think I saw the sun today...

Yesterday's (5/5/09) precipitation at Winchester was 0.27 inches starting from 4:20pm (55.4F) and ended at 9:20pm (53.6F); however, the relative humidity was almost 100% until midnight. Thus, >8 hr of wetness with mid 50's temperature probably accounted for Phomopsis light infection, powdery mildew ascospore discharge, and downy mildew infection. We had overcast weather this morning, and I hope that you had a chance for application (if needed). We are expecting more rain in next few days and next break could be during this weekend.

Much needed break from rain

We experienced a whole day of rain yesterday (5/4/09). Average temperature was 52F, and amount of precipitation was 0.76 inches. The total length of rain event was over 30 hours, including a day before and early this morning. Needless to say, it was long enough for Phomopsis, powdery mildew, and black rot. Our Chardonnay had grown since the last observation. Average was about 60% 3-5 inch stage. Cabernet sauvignon still varies with vines, some vines are showing 6-70% 2-3 inch stage and others are showing 7-80% 1-2 inch stage. We are having a break from rain today in most of central and northern VA. I hope those of whom with concern on Phomopsis had a chance to apply your treatment.

Rain, rain, rain...

The ongoing rain event since yesterday morning (5/3/09, 8 am) has been relatively cold. Starting temperature was about 52F, at mid-night it was 49F, and it has been lower 50's today. It is low, but long enough (>33 hr so far) for Phomopsis to cause light (5-15% disease severity on a cane) to moderate (15-25%) disease. In addition, as of this morning, we have received 0.84 inches of rain since last week (and it’s still raining as of 4 pm, but looks like the end is coming!!). As for powdery mildew ascospore discharge, this rain event met the requirement. A typical rule of thumb for fungicide re-application is “2 weeks or 1 inch of rain, whichever comes first” (Note: you need to adjust the time between applications based on the growth of vine). Please check your local weather for rain and temperature information. There is a banner of “weather underground” on the upper-right side where you can check your local weather information in detail by typing in your zip code (you can even
Update on growth stage: Chardonnay was about 70-90% 3-inch growth; Cabernet sauvignon was still about 50% 1-2 inch growth with a variation among vines. Still raining as of 6:45pm...

Rain again!

Yesterday, Winchester had a drizzle during 3-4am with an average temperature of 58F. It was not a major rain event; however, the relative humidity was almost 100% until 10am. In addition, we had a rain event from 8:30 to 9:30am with an average temperature of 55F. A combined precipitation was 0.08 inches. If you separate these events, it was not enough for Phomopsis to cause disease. However, since the relative humidity was high during the night, I tend to think it was a continuous event. If we combine both rain events, it was enough for a moderate infection (15-25% severity) for Phomopsis. Considering how wet it has been, ascospore discharge of powdery mildew was probably initiated with these rains (especially after 3 am one) whether you combine events or not. (but the morning rain might have washed spores off from leaves... a wishful thining ;)) I was running 10K for Apple blossom festival during the morning rain. It brought temperature down and was nice for me, and after

Warm rainy day

At Winchester, we had rain from 11:50am to 2:20pm (0.12 in) with starting and ending temperature of 62.3 and 67.8F, respectively. Relative humidity dropped soon after the rain and still declining at 5pm and the wind was constantly blowing at 5-10 mph, thus, leaves are probably dried one hour or so after the rain. (If the leafwetness measurement is not available, I use RH>90% as an indicator for the leafwetness after the rain.) Three hours or so was not enough for Phomopsis infection, but it was warm enough for powdery mildew ascospore discharge. Yesterday (4/30/09), we took an advantage of a calm cloudy day and applied our first fungicide application (mancozeb 3 lb/A + sulfur 3 lb/A). Primary target at this point is Phomopsis and Powdery mildew. Although it was either raining or overcast, average temperature in the past few days were in 50's and 60's, and grape were moving its growth stage. About 70% of our Chardonnay was 3-inch stage, and Cabernet sauvignon was abo