Skip to main content

No significant rain so far!

There was a sprinkle in the morning, but so far, we haven't experienced a significant rain event yet at Winchester.

Our Chardonnay and Cabernet sauvignon have been moving its growth stage. It was about 8-90% with 8-9 leaves unfolded with elongation of rachis (E-L 15) for Chardonnay, and about 3-50% E-L 15 for Cabernet sauvignon. Cab sauvignon has more variation among vines, which is consistent since bud break.
I start to see development of black rot lesions on untreated vines. It takes 2-3 weeks to develop fruiting bodies (black specks within tan colored lesion), thus, rain events during 5/5-5/7 or 5/11 are probably responsible for the infection.
I hope you do not see many of these symptoms in your vineyard. If so, you need to protect your berries very well so that it won't affect your yield. Mancozeb, captan, and azoxystrobin (Abound) works well as a protective fungicide application, mycrobutanyl (Rally) works well as a curative fungicide, but I doubt that it will kill actively sporulating lesion. The efficacy will be against new infection. Also, if you happen to have mummified bunches hanging from the old shoots, please take them out. It will serve as a source of inoculum through out the season.

Comments

Popular posts from this blog

2021 Pest Management Guides for grapes (UPDATED 24 March 2021)

Updated: Links below are for the 2021 edition of Pest Management Guides. The first one is for home gardens, and the second is for commercial productions. I asked them to provide by chapter (= crop) and they made changes. :) 1) Visit the page by clicking one of the links below. (It is rather a slow page. Please be patient.) 2) Scroll down until you see "Links to individual chapters." Grapes are chapter 3 for both Home (Home Fruits) and Commercial Crops (Grapes) 3) Once you get to the site, click "PDF", then "Preview", and it will open a new window.  4) Scroll down a bit, and click "Download Version" to download the file to your computer.  2021 Home Grounds  Pest   Management   Guide 2021 Horticulture and Forest  Pest   Management   Guide

At bloom disease management tips

Recent cooler weather seems to have slowed down vine development, but it looks like vines in the south are about to bloom. Bloom is a start of the critical time for cluster infections by downy mildew, powdery mildew, black rot, Botrytis, and ripe rot, because pathogens of these diseases can infect flower parts and develop symptoms later. What I recommend often is the use of protective 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 V. vinifera , and 2-3 sprays for V. labrusca .  If you have hybrids, they are somewhere in between, so, 4-5 weeks to be protected.  As usual, please make sure to rotate mode of action (= FRAC) groups. Since we have not seen many rain events, I think powdery mildew will be the primary target for many of us. But please check your local weather to make sure, some downy mildew susceptible cultivars may still show downy mildew, especially, if there are many

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