As you would expect...

We had a beautiful Saturday here in Winchester. Temperature high was above 90F and as you would expect, vines are pushing their buds. As of noon, Chardonnay was about 10-15% bud break and Cabernet sauvignon was still in bud swell, but buds became larger than previous few days. We'll see what happens tomorrow.

We are expecting slight chance of rain on Wednesday and Thursday. It seems these are isolated thundershowers, thus, I'm not sure it will be enough duration and amount of rain to be concerned about Phomopsis infection. But as I mentioned in the notes, it takes only 4 hours under the optimal condidtions (temperature between 60-70F) for Phomopsis fungus to cause light level of infection. And this fungus starts to be active around this time of the year. If you had Phomopsis in previous years, this fungus can survive for several years and produce spores from infected older canes and trunks. Thus, even if you didn't see Phomopsis problem last year, you may still need to be careful.

Observe growth of vines and weather forecast closely. If your vines are yet to be bud break, you do not need to be concerned. However, if your vines are growing to 1-3 inches, and in coming rain event(s) is expected to last for a while, you may need to consider a fungicide application prior the rain. Protective fungicide application of Mancozeb (Penncozeb, Dithane, etc), Captan, or Ziram have a good efficacy against Phomopsis.

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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

Season's Greetings!

I hope you and your family have a good holiday season and a Happy (and safe) New Year! Thanks again for your support of our programs. Here are some recent media highlights. 😉 The link will open a new window. AHS AREC promotional video that highlights some of our activities. The link did not work... It asks you to log in to VT. I will request the IT people to change the setting, but in a meantime, here's the same video. We also appeared in the Library of Congress project “Winery Workers of Virginia”. One more announcement: I will be moving this blog to a new location ( ext.grapepathology.org ) early next year. I had to make a change due to the email subscription service, which has been terminated. You do not need to change your bookmark or your email subscription. The URL will be forwarded to a new site and your email subscription has been moved to a new site already.

Recent downy mildew risk events

It seems that several rain events have happened over the course of the past two weeks or so. Here is a summary of recent downy mildew risk events, based on the NEWA stations and DMCast. Bristol, VA Fifteen days with potential DM infection event(s) since Sept 1. The latest event happened last Sunday. Floyd, VA Eleven days with potential DM infection event(s) since Sept 1. The last event happened last Friday. Charles City, VA Twelve days with potential DM infection event(s) since Sept 1. The latest event happened yesterday. Central VA Since there was a wide variation among stations, I am listing several around Central VA. Tyro, VA Nine days with potential DM infection event(s) since Sept 1. The latest event happened yesterday. Red Hill and Crozet, VA Only one day with potential DM infection event(s) since Sept 1. Olympic Lake Thirteen days with potential DM infection event(s) since Sept 1. The latest event happened last Sunday. Washington, VA Eight days with potential DM infection event

Virginia Grape Disease Updates

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