Tuesday, March 13, 2018

Slides from NJ "Grape Expectations" meeting

Thank you for who attended NJ's "Grape Expectations" meeting two weeks ago. (I think it is a very cool name for an Extension meeting.) Sorry for not able to post my presentation sooner. I have been out for other meetings.

Click here for slides from my presentation. It will open a PDF file on Google Drive.

Thursday, March 1, 2018

More slides from the 2018 VVA meeting

Here are slides from my student's presentations. The link will open a PDF file on Google Drive. Please note that many of data presented here are still preliminary and we are working on publications.

1) Wong and Nita "Evaluation of Rhizobium vitis ARK-1, A Biological Control Agent For Crown Gall of Grapevine, Using R. vitis Isolates From Virginia Vineyards"

2) Oliver and Nita "Laboratory and field fungicide testing for control of Colletotrichum species isolated from Virginia vineyards"

Friday, February 23, 2018

Slides from the 2018 VVA meeting

Thank you again for those of you attended one of my sessions.

Here are links to my presentations. It will open PDF files on Google Drive.

1) Interactive grape disease management

2) Advanced topic in grape disease management: Fungicide resistance

Please note that we will have more meetings coming up:

16 March 2018
Pruning workshop at Breaux Vineyards (Northern Virginia)

17 April 2018
Vineyard IPM workshop at Early Mountain Vineyards (Central Virginia)

6 June 2018
“Beginner’s” Grape Growing workshop
Virginia Tech’s AHS Jr. Agricultural Research and Extension Center, Winchester VA

We hope to see you there!

Thursday, February 15, 2018

Change in Presidio label: grape is no longer listed.

The label of Presidio has been changed, and unfortunately, the grape was removed from the list of hosts. This means that we no longer able to purchase Presidio to control grape downy mildew.

If you already have it, it is still legally OK to use it for the grape, as long as you keep the original label. (and if you do, please make sure to mix with another mode of action such as mancozeb, captan, copper, since the active ingredient for Presidio is known to have the fungicide resistance issue, and required by the label to mix.)

Thursday, February 1, 2018

Disease considerations at pruning time 2018

Here's this year's handout for pruning time disease considerations (this link opens Google Drive with this year's recommendation for trunk disease management). As I noted in this handout, the first line of defense against trunk diseases that may infect through pruning cut is a cultural control. Make sure to pick dates when you are expecting several days of dry weather.

In this handout, I refer to Topsin-M as a choice of trunk disease management, especially for Botryosphaeria canker, which is very common in our area. The product has been transferred to a new company in 2017, and there are changes in the label. [Note: The US distributor is still the same (UPI), thus, I do not think it will affect where you can purchase the product.] 

If you are using Topsin-M for pruning wound protection, please update your label. You can download the new label by clicking this link (will open Google Drive).

If you are pruning, and wondering whether you can protect pruning wounds from infections by trunk diseases, there is a supplemental label of Rally for control of various trunk diseases (Botryosphaeria, ESCA, and Eutypa).  

You can apply them with a sprayer or as a paint.  It would be a very good idea to use them, especially when you are making a big cut.  The timing of application would be soon after pruning and before a rain. 

Also, double pruning (early winter rough cut followed by the final cut in early spring) showed to reduce 95% of trunk disease in a CA study.

Also, speaking of trunk diseases, I have been involved in a research effort to develop management strategies for various trunk diseases. Please check our project page which contains not only research reports, but also extension information, such as disease keys, management guides, and economic tools to estimate the benefit of trunk disease management over the life of a vineyard.

Saturday, September 9, 2017

A quick reminder before in-coming rain events

Looks like we will likely to have another round of rain from Hurricane Irma sometimes next week.
Just a reminder that we do not have any curative materials for Botrytis and other late season rots. In order to obtain better results, you need to protect your vines before the rain!

Please see the previous post for disease management tips and the list of low PHI materials for each diseases.

Also, it is very important to keep FRAC codes rotated!

Monday, August 14, 2017

Late season downy mildew management and a list of low PHI materials

At Winchester, night time temperature in recent few days is getting pretty low to the point that relative humidity during the night is close to 100%. In addition, we are looking at a thunderstorm forecast tonight that will bring high relative humidity. These conditions favor downy mildew development because downy mildew pathogen prefers to produce spores under dark, humid conditions.

At this point, you do not need to worry about downy mildew infection on clusters; however, they can still infect leaves. Often time, you will initially see infection on the top of the canopy because younger leaves are more susceptible than older ones. Losing the top leaves and laterals are not a big deal; however, once the infection gets severe, it can defoliate many leaves rather quickly (as in the picture above), and that can affect maturing process.

As usual, it is much better and easier to have a preventative program than trying to play the catch-up game. There are many good protective materials for downy mildew, such as Revus products, Zampro, Forum (Please note that these three share the same mode of action (FRAC=45 40 (My mistake. Thank you for pointing it out!))), and Ranman (FRAC=21). In our small trial, fixed copper (FRAC=M1) worked pretty well against downy mildew when we compared with captan (FRAC=M4). Captan worked too, but a fixed copper product lasted longer than captan. Some wine makers do not like to see captan or copper used late in the season, so, this time of the season maybe the best timing to use copper and captan for downy mildew. You can also use a phosphorous acid product (FRAC=33) as well. For some cultivars, you may still use zirum (FRAC=M3) which has a 21-day PHI. Please mix and match to rotate among mode of action groups.

Downy is not the only disease you need to consider. Especially for folks in the northern VA who has been receiving more rain than the folks in the central VA, the risk of Botrytis outbreak can be high. Typically, I post end-of-the-season application tips in September, but it looks like the season is going much faster than a typical year for some of you. Thus, here is a list of fungicides with relatively low PHI (7 days or less) (a PDF file to download). I cannot cover every single fungicide out there, but I tried to cover common ones. Wine making considerations can influence fungicide uses close to the harvest too. Make sure to communicate with your wine maker(s) if they have a preference on the use of fungicides.

As I noted in the previous post, make sure to rotate mode of action for Botrytis because Botrytis pathogen is known for quickly developing fungicide resistance. I prefer to see a mode of action to be used twice or less per season, especially when we deal with Botrytis (with an exception of fungicides with FRAC code starting with "M"). This is also mentioned in the previous post, but wound management for Botrytis is important. The management of the source of wounds such as insects (esp. grape berry moth), or birds, or powdery mildew at early in the season, can result in the management of Botrytis.  Moreover, sour rot pathogens also going after wounds; so, the same wound management would be the key for the sour rot management as well.