Viticulture Field Day and Steak Cookout                 Registration for Viticulture Field Day
Update on Southwest Michigan Wine Grape Happenings
Viticulture Information at MSU Grape Web Site
Contorlling Late-Season Grape Berry Moth
New Fungicides for Grapes in 2004
Michigan Grape & Wine Industry Council News
15th Annual Viticulture Field Day Agenda

The Trade Show will open at 9:00 am. The morning vineyard workshops will start at 10:00 am and the afternoon vineyard workshops will begin at 2:45 pm.

There will be trade show presentations at 12:30 pm and equipment demonstrations at 1:15 pm.

Area Extension Agents along with Michigan State University specialists will be conducting the vineyard workshops. The workshops will cover field identification of insects and diseases, insect control in the vineyard, getting the highest sustainable yields of Concord grapes, grape fungicide characteristics and timing, crown gall disease of grapevines along with other topics.

The wine hospitality will begin at 4:45 pm, with local wineries contributing to the wine tasting and the steak cookout will begin at 5:15 pm.

Early bird registration is $20 per person and is due by July 16. Registration after July 16th will be $25.

The meeting originally scheduled for July 20th has been "rolled" into the Viticulture Field Day and Steak Cookout discussed in this newsletter. A new event that has been decided upon at our May meeting is a two-day trip to Northwest Michigan. It will be August 3 and 4th. Call the office (269-944-4126) for details -- reservations are needed by July 9th.

A new source for viticulture information became available this spring for Michigan juice and wine grape growers. Thanks to initial funding from Project GREEEN, the www.grapes.msu.edu web site has been launched to provide growers with information and timely reports.

The website also contains a weekly scouting report from four juice grape and three wine grape vineyards scouted on Thursday and Friday each week for insects, diseases, and other potential problems. These farms are spread across Allegan, Van Buren, and Berrien counties. This report is then posted online at the start of the following week at the web site in the “current season” section. Checking on the report each week allows growers, scouts, and consultants to see what symptoms are being detected around this area. This is designed to stimulate growers to go and look in their own vineyards to determine whether pest insects or diseases are present on their own vines.

Grape berry moth is a key insect pest of Michigan vineyards, causing infestation of berries and increasing the risk of cluster rots. As part of recent research projects in 2001-2003 we have closely monitored for grape berry moth eggs and larvae on clusters in SW Michigan vineyards. This has provided some insight into when this pest is most active, has helped point toward strategies to improve control of this pest, and has stimulated some new research currently underway to try and prevent infestations at harvest.

Timing: Sampling at vineyards with high pressure from GBM in southwest Michigan has shown that the first egglaying of the season by GBM moths occurred during and just after bloom. This means that in vineyards with a history of infestation by this pest, the first post-bloom spray is the appropriate time for the first insecticide targeting GBM. Depending on the insecticide, this can also control leafhoppers and rosechafers.

One of the most important findings was that egglaying by the second generation of GBM started in middle July around the time of berry touch and continued well into September, with a distinct increase after veráison. The second and third generations of this pest are not distinct, but instead they merge together, leading to difficulty knowing when to time sprays. From experience, mid-July and early August are important times for controlling GBM during most years in southwest Michigan. However, in warm years it will be important not to put the sprayer away at veráison and to keep scouting vineyards to determine whether there is any late-season increase in GBM pressure. Also checking your clusters each week throughout the year is a great way to keep on top of the pest pressure from GBM and other pests. Mid-July through harvest seem to be the greatest danger periods, and regular scouting during this period can help provide information on the level of pest pressure, and whether your spray program is working well. This effort in the middle of the season can help prevent surprises at harvest. Pictures of GBM and its injury symptoms are in MSU's Pocket IPM Scouting Guide or at the website grapes.msu.edu.

Testing a new option for GBM control: As part of our response to the recent increase in late-season activity of GBM, research is underway to determine whether focusing on protecting the clusters in the critical period from mid-July through harvest helps to reduce infestation from berry moth. To do this, two 4-10 acre Concord vineyards with similar history of GBM infestation have been studied at each of four farms. Both vineyards were treated with Danitol at the first post-bloom timing for berry moth control. After that, one vineyard at each farm received Sevin, Danitol, or Guthion according to the grower's typical spray program. The other was treated with Intrepid at 12 oz/acre for control of second and third generation GBM. Intrepid is a new selective insecticide option for grape growers that disrupts development of young berry moth larvae. Spray decisions for the selective insecticide program were based on weekly scouting, and Intrepid was applied with a spreader-sticker in enough water to get good cluster coverage. Most of these high-pressure vineyards received three GBM-targeted insecticides after bloom.

To measure how well the programs controlled GBM, we collected 100 infested berries from each vineyard at three times through the late summer. In vineyards treated with Intrepid, significantly fewer GBM survived from berries compared to samples taken on the same dates from vineyards treated with grower standard programs (Figure1).

Targeting late-season GBM pressure: These results from vineyard-scale trials, coupled with our experience in small-plot trials over the past five years indicate that Intrepid has a good fit against late-season GBM pressure. This is a selective insecticide with long-residual activity and good rain-fastness, but it also has a 30 day PHI. Because of this, growers should focus on the optimal timing if considering Intrepid, targeting the late-season increase in GBM pressure, between berry-touch and veraison. Good cluster coverage is essential with this product, so applications should be made to every row with higher gallonage.

An added benefit of using Intrepid is that it is very safe to natural enemies. In our recent studies we have found that mortality of GBM by parasitic wasps (Figure 2) was greater in vineyards treated with Intrepid than in vineyards receiving a standard insecticide program.

Future directions: We will continue to compare this selective program to conventional programs at the same farms in 2004-5. This will provide information on the effectiveness of both programs against pest insects, and will reveal indirect impacts on natural enemies. We will also measure long-term effects of these programs in pest abundance.

Endura (boscalid) is a new fungicide in another unique chemical class (anilides/carboxamides). Endura is also highly effective against powdery mildew at 4.5 oz/A. It also provides moderate Botrytis control at this rate and very good Botrytis control at 8 oz/A, but does not control any of the other common grape diseases. It appears to have both protective and systemic (post-infection) activity, and becomes rainfast quickly. Endura is not related to any other grape fungicide, so it can be used in alternation with strobilurin and sterol inhibitor fungicides for fungicide resistance management. Because it also provides (rate-dependent) Botrytis control, applications at late bloom and bunch closing will provide this additional benefit on susceptible varieties. Since Endura is prone to resistance development, a maximum of three applications per season is recommended, even though the label allows five. Endura has a 14-day preharvest interval.

Pristine (pyraclostrobin and boscalid) is a new fungicide with a broad spectrum of activity. The active ingredient pyraclostrobin belongs to the strobilurin group, whereas boscalid is the active ingredient in Endura. Pristine has (surface) systemic properties, which allows it to move locally within the leaf and from the top to the bottom of the leaf (translaminar activity). It also becomes rainfast quickly. When used at recommended rates, Pristine is highly effective against powdery mildew, provided that strobilurin-resistant strains are not present. It also provides excellent control of downy mildew (equal to or slightly better than Abound in trials in New York) and black rot (equal to the other strobilurins). Pristine also provides control of Phomopsis and suppression of Botrytis bunch rot. However, it is phytotoxic to ‘Concord’ vines, so cannot be used on this variety. The label also recommends not using this fungicide on ‘Niagara’, ‘Worden’, ‘Fredonia’, and related cultivars because of crop injury concerns. Its most appropriate use will therefore be on wine and table grape cultivars. Pristine has a 14-day pre-harvest interval.

Phosphorous acid (phosphite or phosphonate) products, such as ProPhyt and Phostrol, are starting to be used more widely by growers in the northeast and midwest for downy mildew control. They work similarly to Aliette. Phosphites are readily absorbed by the leaves (and fruit?), and are highly mobile within the plant, accumulating in roots, shoot tips, and possibly fruit. This means that they have some post-infection activity (since they work from inside the plant), but their residual activity is limited (they don't stick around for too long). In tests conducted by Dr. Wayne Wilcox in New York in 2003, these materials showed substantial protective and post-infection activity on foliage. Seven days after the application, protection was still good in the youngest leaves, but declined measurably in older leaves. Fortunately, the youngest leaves are also the ones in greatest need of protection, since they are the most susceptible to disease. Even when leaf infection occurred, spore production was reduced by 95-100% on most leaves in most treatments. Such antisporulant activity should significantly reduce the disease pressure, which is always a concern with downy mildew in a wet season. Note that Ridomil and effective strobilurin fungicides also reduce spore production from developing lesions, whereas mancozeb and captan don't. ProPhyt did not eradicate active lesions, but it did reduce further spore production by about 80% relative to unsprayed leaves. However, under high disease pressure in Chancellor vines, its performance was equivalent to Dithane but far less than Abound or Pristine, which prevented the disease almost entirely. Apparently, 14 days was too long a spray interval under such high pressure. Phosphite products are relatively inexpensive and have a favorable toxicological profile and therefore have a 0-day pre-harvest interval. Some varieties may be vulnerable to burning symptoms, so test out these products on a small scale first.

Michigan Grape and Wine Industry Council News

The Michigan Grape and Wine Industry Council recently completed a Strategic Planning exercise to re-focus the efforts of the Council to meet the changing needs of Michigan’s wine grape industry.

Twenty Year Goal:
To promote market-driven growth of Michigan’s wine industry to support 10,000 acres of wine grape production and 3 million cases of Michigan-produced wine annually by 2024. While achieving those goals, Michigan will become recognized as a world-class wine producing region.

If you have suggestions for how the Council supports research and education activities to assist the wine grape industry, please contact Dr. Miller at 269 657-5568, other members of the committee or Council Program Manager Linda Jones 517 373-9789. If you are new to wine grape growing and wish to receive information from the Council on its programs, please contact Linda Jones.

The Michigan State Fair Wine Competition will be held July 23 at the Kellogg Hotel and Conference Center in East Lansing. A reception follows the competition from 6:30 – 8:00 pm. Grape growers are invited to attend the reception by indicating an RSVP to Linda Jones at 517 373-9789. The 2005 Annual Meeting for the Michigan Wine Industry has been set for March 3 and 4, 2005 at Crystal Mountain.

9:00 a.m. Trade Show Opens

10:00-12:00 noon Morning Vineyard Workshops

Workshop #1 Field identification of insect, disease, nutritional and other disorders of grapes - Mark Longstroth
Workshop #2 Getting highest sustainable yields of Concord grapes in SW Michigan - Marcel Lenz, Leah Clearwater and Stan Howell
Workshop #3 Nitrogen nutrition of grapevines - Eric Hanson and Tom Zabadal
Workshop #4 Evaluating hibernal (Giesenheim selection) for viticulture and wine quality in SW Michigan - Jon Treloar, Leah Clearwater, Stan Howell
Workshop #5 Crown Gall disease of grapevines - Tom Zabadal and Brian Hauch

12:00 noon Complimentary lunch

12:30 p.m. Trade Show Presentations

1:15 p.m. Equipment Demonstrations

2:45-4:30 p.m. Afternoon Vineyard Workshops

Workshop #6 Insect control in the vineyard - Rufus Isaacs and Paul Jenkins
Workshop #7 Strategies for the control of Horsenettle in vineyards - Al Gaus
Workshop #8 Getting highest sustainable yields of GDC and single curtain Niagara grapes in SW Michigan - Kasey Werzba and Stan Howell
Workshop #9 Grape fungicide characteristics and timing - Annemiek Schilder
Workshop #10 Getting the green bell pepper out of our Cabernet Franc and Cabernet Sauvignon - Leah Clearwater, Jon Treloar and Stan Howell

4:45 p.m. Wine Hospitality

5:15 p.m. Steak Cookout