debor039

Most of us are about to finish the critical time when clusters are susceptible to infection by downy mildew, powdery mildew, and black rot.   This critical time varies by varieties, but in general, 4 to 6 weeks and 3-4 weeks from bloom for V. vinifera and V. labrusca species, respectively.   After this critical period, you should be able to relax a bit because these pathogens no longer able to cause disease on berries. So, what’s next?   As usual, disease dynamics really depends on environmental conditions, cultivars grown, and cultural practice, but in general, this is the moment when you will be thinking about late-season diseases such as Botrytis, ripe rot, bitter rot, and sour rot.   The spray timings for Botrytis is at bloom, bunch closure, and veraison.   The pathogen seems to be active throughout the season. The main reason we recommend the application of a Botrytis specific material at bunch closure is that this most likely to be the last opportunity f...

Here are my presentation materials from recent meetings. It will open a new window with a PDF file. 1) Slides from beginner's workshop on 6 June 2018. 2) Handout from the VVA summer technical meeting on 12 June 2018

There will be a meeting in the 23rd of June (Sat) at Rivah Vineyards at The Grove, Kinsale, Virginia. The meeting starts at 6:30 PM. If you are in the Northern neck or surrounding area, please join us.

A few people asked me about the specific location for tomorrow's VVA summer technical meeting. The meeting will be held at Brown Bear vineyards (Formally Spring Hills), and the nearest address is: 229 Spring House Lane, Woodstock VA 22664. Tremain prepared a set of screenshots to help you get there. (Click the images to expand) Spring House Lane is off from Alonzaville Rd. Your GPS may overshoot. When you see the vineyard in front of you, you should see the farm road on your right to get to the garage/barn. See you tomorrow!

Powdery mildew colonies at the center of two leaves in the picture With this wet season, what we think most are downy mildew, black rot, Phomopsis, and Botrytis. Powdery mildew is often associated with a dry season, partially because this pathogen does not require rain for its infection process. However, what they also like to do is grow on shaded leave because they are sensitive to the UV radiation. With very clouded canopy from strong growth triggered from heavy water input (= rain), there are lots of leaves shaded by other leaves. Well, at least that is true in my vineyards... Sure enough, when I took a look at these leaves, I found powdery mildew colonies.  You can see a small white fuzz (= powdery mildew colony) on two leaves in the picture above. Note that how the leaves are shaded. We have a fair number of options for powdery mildew management. Sulfur (FRAC = M2) is an economical option, and there are range of products with different modes of action (= FRAC code).  Exam...

Although our bud break was about two weeks behind of a typical year, the wet and hot May pushed our vines forward rather quickly.  Many people in northern VA are about to see blooms (our 3-year old young Chardonnay vines are trace bloom), and I am sure rest of regions are going through bloom by now. This means that many of us are in the critical time for cluster infections by downy mildew, powdery mildew, and black rot. Bloom time is also the critical period to prevent Botrytis, ripe rot, and bitter rot, because pathogens of these diseases can infect flower parts and develop symptoms later. With all the rains we observed, many people are concerned about downy mildew and black rot. In our vineyards, I did not see much sign of downy, but there are many leaves with black rot. It is probably because we did not have major downy mildew outbreaks in past three years. We do have materials with kick-back activities against downy (Ridomil products (FRAC=4), phosphite (FRAC=33, Prophyt, Phost...

I have added more information to the yesterday's post. Please check it out. Options against current rainy condition .