Skip to main content

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.
Labels:

Comments

Post a Comment

Please leave your comment here. In order to avoid spam messages, l moderate comments, thus it may take a few hours for your comment to be posted on the page.

Popular posts from this blog

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
Post a Comment
Read more

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. 
Post a Comment
Read more

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
Post a Comment
Read more