Skip to main content

Seasonal disease management reminders at bloom time



Many people in northern VA are about to see blooms (our Chardonnay vines are trace bloom as of June 2nd, the one on the picture is one of the few with many open flowers), and I am sure rest of regions are going through bloom by now.  Therefore, many of us are in the critical time for cluster infections by downy mildew, powdery mildew, and black rot.  Bloom time is also critical period to prevent Botrytis, ripe rot and Bitter rot, because pathogens of these diseases can infect flower parts and come back later.

We do have materials with kick-back activities against downy (Ridomil products, Phosphonates, etc.) and black rot (myclobutanil, etc.), but infection on flowers and young fruits can happen very fast.  Unless we have a very dry season, this is the time where you have to be proactive.  Thus, what I recommend often is use of protectant materials to protect tissues for 4-6 weeks for V. vinifera varieties, and 3-4 weeks for V. labrusca varieties, which should translate into 3-4 sprays for vinifera, and 2-3 sprays for labrusca.  Please make sure to rotate mode of action groups.

Here is an example from our experimental vineyards.
1)   At bloom: mancozeb + sulfur + myclobutanil or another DMI + Vangard (+ phosphonate, if it rains a lot)
2)   First cover: mancozeb + sulfur + Quintec (+ phosohonate, if it rains a lot)
3)   Second cover: mancozeb + sulfur + myclobutanil or another DMI (+ phosohonate, if it rains a lot)
4)   Third cover: captan + sulfur + Quintec (if needed, if I do not see any evidence of powdery mildew, I may omit Quintec from this spray) (+ phosohonate, if it rains a lot)

The spray interval depends on the weather conditions; so, I cannot give you a specific number.  However, in general, I would aim for shorter intervals for sprays #1, #2, and #3 (7 to 12 days), but I may relax a bit for #3 and #4 (10 to 14 days), if weather condition does not favor downy or black rot.   

Please note:
  • I am saving my DMI (Rally, Elite, Mettle, Revus Top, Luna Experience, etc, etc.) and Quintec (or Vivando, Torino, or any other new powdery material) usages for the critical period, thus this is the only time we spray these materials. 
  • I would like to use a mancozeb product around bloom because it has activities against multiple pathogens including pathogens for black rot and ripe rot.   
    • Captan is not as effective as mancozeb when it comes to black rot management.   
  • The third cover may become too close to the 66-day PHI, so, you need to be careful with the usage of a mancozeb product.

Of course the example given above is just one example, and there are many other options.  For example, there are many new materials became available for powdery mildew management in recent years.  Thus, as usual, please refer to our PMG for more details.

Comments

Popular posts from this blog

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

A quick reminder for late-season disease management materials in preparation for Ida.

  In preparation for hurricane Ida, here is some information that you may find useful (This is a repeat of the previous post, but I received some emails asking for them.) 1)  List of short PHI fungicides for late-season diseases (will open a pdf file) 2)  Updated presentation from the last virtual field day (will open a pdf file). Recent downy mildew risks Many of us have been experiencing more rains lately than the past several months, here are a number of days with downy mildew risk events in the past two weeks based on the NEWA’s DMCast. Many of these rains have been sporadic in terms of area and time it covered, so, use these numbers as a guide. Bristol: 14 days (latest was on 8/30) Floyd: 9 days (latest was on 8/29) Charles City: 14 days (latest was on 8/30) Tyro: 7 days (latest was on 8/30) Red Hill: 5 days (latest was on 8/29) Washington: 8 days (latest was on 8/29) Winchester: 9 days(latest was on 8/29) It is probably a good idea to protect your vines against downy mildew in a