Sunday, June 28, 2009

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...

Thursday, June 25, 2009

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 mildew fungus to spread spores (ascospores) from its overwintering structure (cleistothecia). Thus, as temperature goes up, we probably see more powdery mildew development. As you know, we have several choices of fungicides for powdery mildew, so, you do not need to panic, but I just want to remind you that it's coming.

Here are some pictures from our vineyard.
The white circle on the center is powdery mildew.
Up close and personal...
(You can almost see spores!)Powdery mildew prefers a location with diffused sunlight.
Such as the shaded leaf on the center of the picture.
Do you see powdery mildew?
I do. ;)

Wednesday, June 24, 2009

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.

Tuesday, June 23, 2009

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!!

Sunday, June 21, 2009

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 right rains during the night, but RH was too low to account for a major disease event.

Thus, we had a series of weather events which is suitable for downy mildew infection and spore development. If you are planning to apply fungicides next week, it is probably a good idea to include a material that has a good curative (kick-back) activity against downy mildew (Ridomil products, Phosphorus acid products). If you have seen black rots, it may be a good idea to include myclobutanyl (Rally) in your spray mix. Rally has a good curative activity against black rot.

Other thing I noticed in our vineyard is powdery mildew. It is not to the point of concern, but I start to see symptoms here and there. Do not forget to add a material for powdery mildew. Sulfur is a cheap broad spectrum material for powdery mildew.

As you are aware, 4 to 5 weeks after bloom is the critical time for black rot, downy mildew, and powdery mildew infection on berries. Please make sure to protect your bunches.

FYI: our Chardonnay is 100% BB size and Cabernet sauvignon is 50% BB size.

Monday, June 15, 2009

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...).

Saturday, June 13, 2009

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 gallery for your reference. I hope you don't see bunch infection as we found on our untreated vines.

Downy mildew on leaves (oily spot lesion) and bunches
Close up of infection on a bunch
You can observe sporulations (white mass)
Close up of under side of a leaf with heavy sporulation
We are talking about millions of spores at this point.
(= early season management is important!)

Thursday, June 11, 2009

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...

Tuesday, June 9, 2009

Thunderstorms!

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.

Monday, June 8, 2009

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.

Saturday, June 6, 2009

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 of rain (including incoming ones) may not give you an option. Please spend some time to make an assessment of the situations in your vineyards.

Here are some of potential scenarios.
1) Last application: two weeks ago, mancozeb + sulfur (or similar protective fungicides), vines are in bloom or post-bloom, little or no rain, expecting rain this week --> You will have a wide range of choices. You may stick with economical protective fungicide (e.g. mancozeb + sulfur).

2) Last application: one week ago, mancozeb + sulfur (or similar protective fungicides), vines are in bloom or post-bloom, little or no rain, expecting rain this week --> Here comes a judgment call. If you did not experience rain in the last week, you may able to wait until next series of rain is over and hit vines with curative fungicides (Ridomil or Phosphorus acid for downy, Rally for black rot, etc) plus a broad spectrum protective fungicide such as mancozeb products.

3) Last application: two weeks ago, mancozeb + sulfur (or similar protective fungicides), vines are in bloom or post-bloom, had 2-3 days of rain, expecting rain this week --> Downy mildew and black rot might be your major concern. Consider using products with curative activities (Ridomil or Phosphorus acid for downy, Rally for black rot, etc) plus a broad spectrum protective fungicide such as mancozeb products.

4) Last application: one weeks ago, mancozeb + sulfur (or similar protective fungicides), vines are in bloom or post-bloom, had 2-3 days of rain, expecting rain this week --> Downy mildew and black rot might be your major concern. Depends on how much rain you received, the protection from mancozeb and sulfur may be gone by now. Consider using products with curative activities (Ridomil or Phosphorus acid for downy, Rally for black rot, etc) plus a broad spectrum protective fungicide such as mancozeb products.

5) Last application: one weeks ago, Ridomil+ sulfur (or similar systematic fungicides), vines are in bloom or post-bloom, had 2-3 days of rain, expecting rain this week --> Ridomil should provide you a coverage for 10-14 days. However, consider the history of your vineyard and current situation. If you had a issue with downy mildew or black rot last year, you may need to be on top of the situation. You can scout your vineyard and look for symptoms of downy or black rot (please see images below). If you find downy mildew or black rot in your vineyard (say, few leaves per vine), then you may need to think about protecting your leaves against the upcoming rain events. If you know vineyards are clean (historically and right now), then you may be able to hold off your application until after the upcoming rain events. Either way, downy mildew and black rot might be your major concern. Consider using products with curative activities (Ridomil or Phosphorus acid for downy, Rally for black rot, etc) plus a broad spectrum protective fungicide such as mancozeb products.

The other disease of concern would be Botrytis. It can cause infection on flowers and cause problems later in the season. You may want to include some of Botrytis materials such as Elevate, Endura, and Pristine in your program. And although I did not mention in the previous scenarios, you still want to protect your vines from powdery mildew. Sulfur would be a nice and economical insurance. If you decided to use other products, such as Sterol-inhibitors, please make sure you rotate the mode of action of the chemical.

Here are pictures of downy mildew and black rot for your reference:

Downy mildew "oily spot" symptoms, upperside of the leaf
Downy mildew sporulation, underside of the leaf
Black rot symptom

Friday, June 5, 2009

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.

Thursday, June 4, 2009

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.

Tuesday, June 2, 2009

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.

Monday, June 1, 2009

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.