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 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

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(s) since Sept 1. The latest event happened last Sunday.

Winchester, VA

Seven days with potential DM infection event(s) since Sept 1. The latest event happened last Friday.

Some rain events are sporadic and the amount of rain or length of leaf wetness can vary even within a few miles. Thus, please make sure to check your local weather. 

In general, it is probably a good idea to protect your vines against downy mildew this time of the season, and if you think your previous application was washed off from the rains, add a phos acid to your tank mix for your next spray.

List of short PHI fungicides for late-season diseases (will open a pdf file)

 Please find a link below to download a new disease management guide for non-bearing grapes. As with the other VCE guides, you need to click on the “Preview” icon, which will open a new window, then click on the “Download” icon to obtain a pdf copy.

https://resources.ext.vt.edu/contentdetail?contentid=3226&quantity=1&productprice=0&contentname=Fungicide%20Spray%20Guidelines%20for%20Non-bearing%20Vineyards

Also, I updated a list of fungicides that you can obtain from home garden centers. I saw several new products, but unfortunately, many of them do not list grapes on their label, so, the list is identical to the old version. If you know of other products that can be used for home gardens, please let me know.

Home-garden-fungicides-2021Download

 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 preparation for Ida, and if you think your previous application was washed off from the rains, add a phos acid to your tank mix for your next spray.

Recent rains and more rains in the forecast made me think of downy mildew. Let's take a look at what the NEWA DMCast model says about downy mildew risks from the past two weeks.

Westfield, NC (South of Stuart, VA)

There were six DM risk events, including one that happened today. 

(Note: we have a new weather station in Bristol. You can check the weather data, but the DMCast model is not working yet. I notified the NEWA about the lack of DMCast outputs.)

Floyd, VA

Thanks again to those of you who made it to the meeting. It was nice to have a face-to-face meeting after the whole thing we are in together.

Here's my handout from today's meeting.  It will open a new window with a pdf file.

I mistakingly placed Vivando, which does not work on downy mildew, on the downy mildew table. Please strike it out or use the updated version below.

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).

Thank you again for participating in our meeting.

Please find two materials from today's presentation.

1) List of short PHI fungicides for late-season diseases (will open a pdf file)

2) Today's presentation (will open a pdf file).

Have a good rest of the season, and hope to see you next week at the VVA summer technical meeting!!

This is another reminder about downy mildew. This post is probably more applicable to those of us who are in northern VA. We received several rain events in the past two weeks. Not all of them accounted for downy mildew infection risk events; however, recent warm and humid nighttime weather probably encouraged the downy mildew pathogen to produce spores. 

Here are recent downy mildew infection risks based on the NEWA's DMCast.

Floyd, VA: Downy mildew risk events on 7/6, 11, and 15.

(note: the temperature sensor has been fixed recently, and that's why it shows records from mid-June.)

Red Hill, VA and Olympic Lake: If you are in central VA, please check your local weather station. It seems that the numbers vary quite a bit among them.

Red Hill: downy mildew risk events on 7/2 and 8.

Olympic Lake, downy mildew risk events on 7/2, 6, 8, 11, 12, 15, and 16.

It looks like many of us received some rain in the past few days, and we may see another rain toward the end of this week.

Here are recent downy mildew infection risks based on the NEWA's DMCast.

Floyd, VA (note: the temperature sensor has been fixed recently, and that's why it shows records from mid-June.)

Crozet, VA (note: the precipitation sensor has been fixed recently! We really appreciate the willingness and commitment of the personal weather station owners!)

Presentation slides

Thank you to those of you who were able to make it to the meeting today. Here are slides from today's presentation (open PDF). 

Up-coming meetings

• Eastern Section American Society for Enology and Viticulture annual meeting (7 – 8 July): The ASEV/ES meeting will occur on-line this summer. See https://www.asev-es.org/ for details on the meeting, which will include research presentations and a panel discussion entitled “Future Grape Cultivars for Eastern North American Growers”.
• Eastern Viticulture and Enology Forum (13 July): The July 13th meeting is the next of a series of 4 virtual meetings organized by viticulture and enology extension specialists at Penn State, Cornell, and Virginia Tech. In addition to regional round-ups of seasonal progress, specialists from around the eastern US address pre-submitted questions from participants. Registration instructions and additional information about the meetings can be found on the attached Word document.
• Virginia Vineyards Association/Virginia Tech Summer Technical meeting (28 July)
• Virginia Tech’s AHS Jr. Agricultural Research and Extension Center is pleased to host the Virginia Vineyards Association (VVA) and others to a viticulture/enology field day on Wednesday 28 July 2021. This will be largely outdoors, in-person, and in the heat of late-July. If you are not fully vaccinated for Covid-19 (2+ weeks post final vaccination), please wear a face-mask. Meeting registration information will be available soon at the VVA website:  https://virginiavineyardsassociation.org
• The day-long program, starts with registration at 8:00 am and includes the following, with much of the content simultaneously translated to Spanish:
• Review of viticulture and grape pathology research projects at the AREC (Use of ABA to delay budburst, field trial of enzymatic fungicide for powdery mildew management; use of rainshields under field conditions; novel wine grape variety research, and more)
• Invited speaker on ripe rot and other late-season rots of grape
• Demonstration of under-trellis vegetation management options (Winchester Equipment)
•  Catered lunch
• Hands-on canopy assessment and late-season tune-up
• Grower’s experience with Petit Manseng, including tasting of different Petit Manseng wine styles
• An opportunity to socialize with other industry members

It looks like we all received much-needed rains, which is good for vine growth. However, since most of our vines are still within the critical period for cluster infection by downy mildew, powdery mildew, and black rot (~ until 6 weeks after bloom for V. vinifera, ~ 4 weeks for V. labrusca), it also means that we may have had risk events for disease infection. Since the month of May was dry, I think the overall disease risk is low for downy, black rot, and other diseases that are driven by rain (e.g., ripe rot and Botrytis), but I just want to go over recent NEWA outputs. 

Disease risks from the recent rain events

Westfield (Close to Bristol, VA)

It seems that the southwest VA received quite a bit of rain over the past two weeks! I would think many cultivars are close to the end of the critical period, but if you are concerned, a DMI fungicide and a Ridomil or Phos-acid product are effective for black rot and downy mildew, respectively. These materials can be applied a few days after the rain (2-3 days for downy, 3-4 days for black rot) to stop the ongoing infection process.

I would not take Phomopsis risks very seriously at this time of the season unless you have a heavy infestation (i.e., you see Phomopsis infection on rachis and berries very often). Most of our vineyards are relatively clean in terms of Phomopsis. 

Richmond

(We cannot calculate downy mildew risks at Richmond because the station at Richmond is not a NEWA station.)

A daily summary shows precipitations starting from 28 May and as with Wakefield, they experienced frequent rain events. Please see the comment above.

Crozet

It seems that there was a gap of about ten days from previous rain events. If you are concerned about downy or black rot, please see the comments above. 

I don't know why powdery mildew risk is low. There were several days in the previous week that the maximum temperature was close to 90F, and maybe the model is reflecting it. However, since the daily average temperatures have been mid- to upper-70F, I think the powdery mildew pathogen is still active.

Winchester

The DMCast shows the risk of downy mildew was low, even though we had 22 hours of leaf wetness on the 11th. This is probably due to the low temperature. If you are concerned about black rot or downy mildew, please see the comments above.

What to do if you receive more than 1 inch of rain soon after you sprayed?

Due to the rain, I received several questions about actions after the rain. Typically, our general recommendation is to re-apply materials after 2 inches of rain or two weeks, whichever comes first. (Note: I often recommend a 7- to 10-day application from bud break to the end of the critical period since grapevines grow so quickly.) However, if you have more than 1 inch of rain, it is probably better not to wait for two weeks.

If you are interested, please check the article from Dr. Schilder about rain and wash off of fungicide. Her work suggests that although only a 0.04 inch of rain can wash a certain percentage of material from the leaf, it takes about 1-2 inches to actually causing a negative effect on the efficacy since the rate you apply is typically much higher than the threshold for the efficacy of the material. With the newly applied material, they observed good efficacy against Phomopsis from Captec and Ziram even after 2 inches of rain. 

Another factor is whether you had enough time from the time of the spray and rain. In general, many fungicides we use require ~1.5 to 2 hours to be dry and adhere to the plant surface.

The take-home message here is that if you had 1-2 inches of rain soon after your previous application (with enough drying time), there is good efficacy left from the spray. I would not wait for two weeks, but you don't need to rush out to re-apply immediately after the rain. 

It probably depends on the sprayer, but if the rain started within an hour of your spray, you may need to go back and re-apply sooner than later.

Just a quick note that recent rain events were risk events for downy mildew based on the NEWA DMCast model. It seems that northern VA received more and longer rain events. In addition, we may see more rain toward the end of next week.

Since we have been experiencing a very dry season, I was not really thinking about downy mildew. However, during recent vineyard visits, I have noticed downy mildew on leaves, and sure enough, I saw some downy mildew lesions on leaves in one of my research blocks too.

If you are due to spray soon, grow downy mildew susceptible cultivars (e.g., Chardonnay, Vidal, etc.), and/or have seen a considerable amount (or duration) of rain recently, it may be a good idea to include a Phos acid material (e.g., Prophyt, Phostrol, Agri-Fos, etc.) in the tank mix as insurance. Please note that if you use a copper material, a combination of copper and phos acid can cause phytotoxicity. Since many of our vines are in the critical period to protect clusters from downy mildew, powdery mildew, and black rot, the use of a Ridmil product may also be a good idea.

For more details on "at bloom" fungicide applications, please refer to my previous post.

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.

Since the past winter was more or less steady and mild, in terms of temperature fluctuations, there are less likely that many of us saw the minimum temperature at 15F or lower. For example, at Winchester, we saw 14.5F on the 21st of February, and that's it for this winter. The risk of Pierce's disease will increase with a warmer winter. I.e., less than three nights with a minimum temperature of 15F or lower will decrease the risk of Pierce's disease. 

Thus, especially people in the south and eastern part of the state may need to prepare for the management of sharpshooter leafhoppers, which are the vectors of Pierce's disease. Some growers in the eastern VA use insecticides for sharpshooter leafhoppers from May to June, so, I thought it is probably a good idea to sent out a reminder. 

Entomology is not my area of expertise, thus, I will copy the information from our Pest Management Guide, page 8.

In some vineyards in the eastern part of the state, sharpshooter leafhoppers, the vectors of Pierce’s disease are of concern. While research is needed on the vector relationships and timing in Virginia, the neonicotinoids Admire Pro (1.0 fl oz). Assail 70WSP (1.1-2.3 oz/A), Assail 30SG (2.5-5.3 oz/A), Belay Insecticide (4.0-6.0 fl oz), Scorpion 35SL (2.0-5.0 fl oz), Venom 70SG (1.0-3.0 oz/A), and Venom 20SG (0.44-0.66 lb/A) are registered for control of sharpshooters. Use the higher rates for higher pressure. In addition, Scorpion and Venom are registered for soil application (9.0-10.5 fl oz; 5.0-6.0 oz/A respectively), as is Admire Pro (7.0-14.0 fl oz/A). Soil applications should be applied between bud-break and pea-berry stage and should be considered when there are three or fewer nights below 15˚F during the preceding winter. The neonicotinoids share a common mode of action; avoid overuse to avoid resistance.

Besides neonicotinoids, the following pyrethroids are registered for sharpshooter control: Esteem (5 oz/A), Danitol 2.4EC (10.67-21.33 fl oz/A), Brigade 2EC (6.4 fl oz/A), and Baythroid 2EC (1.6-3.2 fl oz/A). Danitol is limited to two applications, Baythoid to four applications, and Brigade to two applications at the low rate, one at the high. In blocks where Spotted-wing drosophila will need to be controlled, early use of pyrethroids will decrease the number of applications available in late season.

Consult http://www.virginiafruit.ento.vt.edu/PDsharpshooters.html for updated information

 Thank you to those of you who were able to join us today. Here are some of the items we discussed.

1. Slides from today's presentation (will open a pdf file in a new window)
2. RSS feed address for this blog (I posted under "Resources" too)
1. You can also subscribe via email using the menu showing on the upper left part of this blog. Google will drop the email subscription service in July, but I will come up with another way to send you reminders. Thus, if you wish to be included after July, please go ahead with the subscription service.
3. Link to my grape disease management workshop presentation videos.
1. Please note that the closed captioning is most likely not working. I created CC with the Canvas site we used in the workshop. If you wish to watch them with CC, please send me an email so that I can send an invitation to Canvas site. Unfortunately, I don't have time to work on YouTube version right now. I will focus more on YouTube version next year.
2. I will keep it available for several weeks.

Upcoming virtual vineyard meetings

The viticulture group at the AHS Jr. AREC will be hosting a series of four monthly, on-line viticulture meetings starting Thursday, 22 April 2021. The content of each meeting will vary somewhat and will involve extension specialists who will provide seasonal updates on vineyard management, pest management topics, and emerging weather, pest or disease issues. An initial topic of each of the 4 planned meetings will be a statewide grape development roundup gathered from our “sentinel vineyard” cooperators located around the state. Each meeting will last about 2+ hours, starting at noon.  At this point, the meetings will be on-line, but stay tuned for at least one on-site meeting which we plan to host at the AREC in late-July. 

The meeting dates (noon start) are:

1)     April 22, 2021 12:00 PM (EDT)

Register in advance for this meeting:

https://virginiatech.zoom.us/meeting/register/tZ0pceigqTMrGdOSA5D6uvJUEfYaVZKLVER7

After registering, you will receive a confirmation email containing information about joining the meeting.

2)     May 20, 2021 (12:00 PM) [Registration information will be issued]

3)     June 24, 2021 (12:00 PM) [Registration information will be issued]

4)     July 22, 2021 (12:00 PM) [Registration information will be issued]

If you are a person with a disability and desire any assistive devices, services or other accommodations to participate in these meetings, please contact Tremain Hatch, AHS Jr. AREC at (540) 232-6032 during business hours of 9 a.m. and 5 p.m. to discuss accommodations 3 days prior to the event. 

Updated PMG

I fixed several errors on the 2021 Commercial Grape PMG. The changes are made on the fungicide efficacy table. If you wish to download the newest version, please use the links from this posting.

Community interest:

Revalation Vineyards, located in Madison County, is seeking a highly motivated individual who will work in its expanding vineyards and orchard. The tasks include planting, training, pruning, manual and mechanical weeding, mowing, hilling, up and down, spraying, canopy management, netting, harvesting as well as building trellises. This is a year-round full-time position with immediate starting date. Applicants must have extensive experience driving a tractor, be able to work independently and be detail-oriented. Starting compensation is commensurate with relevant experience. If interested in this opportunity, please send a cover letter and your CV to info@revalationvineyards.com.

Our eight years old chardonnay is about 50% bud break as of yesterday, and I am sure that growers in the south have seen buds and shoots already with the early season cultivars. Although the chance of precipitation seems to be low for a while, it may be a good idea to review Phomopsis management, just in case. It looks like rain events that happened in the past few days accounted for Phomopsis disease risk events according to the NEWA.

It looks like our Chardonnay buds are swelling, which probably means that growers in the south and central Virginia either start to see bud break. Then the forecast is calling for rains next week. I guess it is a typical Virginia spring.

One of the diseases you need to consider soon after bud break is Phomopsis cane and leaf spot. It causes minor leaf spots, which are more evident to our eyes, but necrotic lesions cause more critical damage on shoots and rachis. It also causes berry rot; however, it is not common with wine grapes because of our spray programs. Some cultivars, such as Viognier, Cabernet Sauvignon, and Seyval Blanc, are more susceptible to Phomopsis than the others.

Phomopsis spores can cause infection requires water, and Phomopsis spores can germinate in a relatively cooler environment (the upper 40s). This pathogen tends to produce spores in spring from previously infected canes and cordons. Thus, springtime rain events are ideal for the development of Phomopsis. It is vital to protect young tissues when they come out from the older canes and trunks because we do not have any curative fungicides against Phomopsis. 

This disease typically takes a while to establish in the vineyard. It may take 4-5 years for Phomopsis to become noticeable after you start a new vineyard. However, once established in a vineyard, it is difficult to get rid of this disease. The fungus survives in canes and trunks that were infected in previous years, and it can cause damages to cordons and trunks. In other words, this disease can cause long-term damage to cordons and trunks.

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 useful protective materials against Phomopsis. Since shoots will proliferate quickly, you may need to spray several times against Phomopsis, depending on how much rain we receive. One or two applications, starting from 1 to 2 inches shoot length and repeated seven to ten days apart, is sufficient in a typical year. After that period, your downy mildew or black rot applications, which happens in the late spring, most likely cover Phomopsis. 

QoI (FRAC = 11), such as Abound and Pristine, as well as SDHI (FRAC = 7), such as Luna Experience, Miravis Prime, Aprovia, and Aprovia Top are effective too. However, you probably 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 (e.g., ripe rot and bitter rot). 

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, 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 in addition to the list above, Topsin-M (FRAC = 1) is also known to be effective.

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

Here are links to the 2021 edition of Pest Management Guides. Unlike the past years, all the crops are combined together. (i.e., I cannot separate the grape section.) Once you get to the site, click "PDF", then "Preview", and it will open a new window. Then you need to click "Download Version" to download the file to your computer. Once the document is downloaded, you can search the document to find "grapes".

2021 Home Grounds Pest Management Guide

2021 Horticulture and Forest Pest Management Guide

• March 16th (1 - 4 PM): Grape IPM workshop
• This is a lecture-style meeting where we cover topics in disease, insect, and weed management, WPS, and Viticulture
• March 31st (12 - 1:30 PM): Grape disease management workshop (in English)
• This workshop aims to help you plan your disease management plan. We will go over seasonal disease management together.
• April 1st (12 - 1:30 PM): Grape disease management workshop (with Spanish translation)
• This workshop aims to help you plan your disease management plan. We will go over seasonal disease management together.
• April 9th (12 - 1:30 PM): GrapeIPM.org training
• This is a training session for a new online pesticide management and decision support system for grape growers. We will help you set up accounts and first vineyard(s), demonstrate key functions, etc.

Thanks again to those of you who were able to attend my workshop last Friday.

As we discussed, here is the slide set from my presentation (pdf, opens a new window). 

We are also planning to have several meetings in March and April. All will be online events.

I have updated my fungicide application template that I have been using for my fungicide guides. If you are interested in it, download it from this link. This will open a new Google Doc page, which says it is "View Only"; however, you can download the file. Select "File" from the top menu of Google Drive, and you will see the "Download As" submenu which has several options for the file type.

Many thanks to Mr. Bob Romsey who shared the original template with me!

FYI: They are looking for a winemaker, if you are interested see below for more detail.

https://www.winebusiness.com/classifieds/winejobs/?go=listing&listingid=202628