Saturday, April 14, 2018

Early season disease (Phomopsis and Anthracnose) management tips

Our Chardonnay and some of the hybrid vines are in bud swell stage as of this week, and others are tagging along.  It looks like we will see bud break very soon with warmer temperature (but next week should be cooler).


One of the diseases you need to consider this time of the year is Phomopsis cane and leaf spot.  It causes minor leaf spots, which is more obvious to our eyes, but the more important damage is caused by necrotic lesions on shoots and rachis. It also causes berry rot; however, it is not common with wine grapes because of our spray programs. Materials for black rot and downy mildew are often effective against Phomopsis. Thus, the fungicide coverage for these diseases is also working as management of Phomopsis, especially later in the spring and early summer. Some cultivars, such as Viognier and Seyval Blanc, are more susceptible to Phomopsis than the others.

Phomopsis takes a while to establish in the vineyard. It may take 5-6 years for Phomopsis to become noticeable if you start a new vineyard. However, once established in a vineyard, it is difficult to get rid of this disease. Phomopsis tends to become noticeable as a vineyard gets older because of its life cycle. The fungus survives in canes and trunks that were infected in previous years. During the spring, it will produce spores on the surface of infected tissues, and these spores are splashed by rain onto new shoots or leaves. Luckily, the pathogen (Phomopsis viticola) produces spores mainly during the springtime. Thus, unlike the other diseases we face, there is only one major infection period throughout the season. Because of that, the spread of Phomopsis does not happen rapidly as other grapevine fungal diseases, such as downy mildew.

Phomopsis spores can cause infection under the relatively cooler environment (the upper 40s). Thus, springtime rain events are ideal for Phomopsis to produce spores and cause infection. Unfortunately, we do not have curative fungicides for Phomopsis management; therefore, it is important to protect young tissues when they come out from the older canes and trunks. Since shoots will grow rapidly, you may need to spray 1-2 times against Phomopsis, depending on how much rains we receive.
 
If rain events are coming into the picture after bud break, mancozeb (FRAC=M3, Penncozeb, Dithane, Manzate, etc.), Ziram (FRAC = M3), and captan (FRAC = M4) are effective protective materials against Phomopsis. In a typical year, one or two applications from 1-2 inch shoot growth will be sufficient, because your downy mildew or black rot applications, which happens in the late spring, will cover Phomopsis. QoI (FRAC = 11), such as Abound and Pristine, as well as SDHI (FRAC = 7), such as Luna Experience and Aprovia, work too. However, you don't want to use them this early in the season because you will need these materials for the latter part of the season to control other diseases.  Once again, protection is the only mean of chemical management because no materials are effective after the infection.

The other disease that you may need to consider around this time of the year is Anthracnose, which is more common with a certain hybrid species. Typical symptoms are black necrotic lesions on leaves,  shoots, and fruits, and often time, the black lesion has an ash-colored center, as if you burnt the leaf or shoot tissue with a cigarette. The management strategies will be similar to that of Phomopsis, and Topsin-M (FRAC = 1) is also known to be effective. For more information on Anthracnose, please refer to this link (Michigan State's Extension Website on grape Anthracnose management).

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.