Skip to main content

Reminder on downy mildew

Just a reminder on downy mildew management: although the month of July was dry until this week, many of us had a very wet early summer that fostered downy mildew development. In addition, during the last several days, the night time temperature was in low 70s and RH was 95-99%, which was an ideal condition for downy mildew spore production.

Thus, if you have not, make sure to protect your vines against downy mildew when you have a chance. If you think you have missed the window, we still have some options.

We have materials with kick-back activities against downy (Ridomil products (FRAC=4), phosphite (FRAC=P7, Prophyt, Phostrol, etc.). One of two Ridomil product (Gold MZ) has a mancozeb, which has a 66-day PHI, so, unless you have a late season red, you probably need to use the other formulation, which is Ridomil + copper. Both Ridomil and phosphite are good with kick-back, but you probably want to add a protective material to cover both directions. Examples would be captan (FRAC = M4), or ziram (FRAC = M3), or Revus, Forum (FRAC=40), or Zampro (FRAC=40+45), or Ranman (FRAC = 21)). Please note that Revus, Forum, and Zampro all have the same mode of action (i.e., you cannot rotate among these three.) Also, copper materials (FRAC=M1) works well against downy mildew. If you decide to use a copper, my current preference is one of newer materials (e.g., Cueva, Badge, etc.), which have a lower copper concentration (but still works well).

As Tony indicated in his newsletter, keep eye on the concentration of the phosphite material. If you exceed the amount, it may end up with phytotoxicity.

Many people have asked me about the combination of copper and phosphite. I have heard that there is a pre-mixed product of copper and phosphite sold in Europe, so, these compounds can be mixed. However, both products are sensitive to water pH. It needs more research, but I have a feeling if you miss the sweet spot on the pH, it can cause toxicity on vines. So, if you wish to try, my recommendation is to make sure you have a good pH (close to the neutral), and try it on a small block of your vineyard (or even a few vines). Also, I wonder about different copper formulations (sounds like a good summer project for us. we will see...)


Labels:

Comments

  1. AnonymousAugust 3, 2018 at 10:48 AM

    You have no idea how helpful and useful these timely posts are for us- thank you
    Toni
    Granite Heights Winery

    ReplyDelete

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 e...
Post a Comment
Read more