July 2001
Volume 2   Issue 3

Table of Contents (click on Title)

Grape Resources on the World Wide Web
Post-Bloom Management of Grape Berry Moth
12th Annual Viticulture Field Day/Steak Cookout
Annual Membership Fee Begins 2002
Where Did All the Grapes Go?
Michigan Grape/Wine Industry Council Events

Viticulture Field Day Registration

Grape Resources on the World Wide Web
By: Mark Longstroth, Dist. Extension Horticultural Agent

Did you know the Michigan Grape Society has a website? It is part of the MSU Extension, Van Buren County’s site. Eventually, they may even move to there own website and not be part of MSUE.

During the course of a year I get a lot of calls about grapes. Many of these come from commercial grape growers in Southern Michigan. About a quarter of these calls come from people who are new to grapes and almost always they want me to send them everything I have on grapes. I spend a large amount of time talking with these people. Homeowners are pretty easy, sometimes they just want to know what is wrong with their grapes. People who are interested in wine grapes are harder to please.

I have built up a large web site for commercial and hobbyist grape growers. These grape pages can be found at the Van Buren County MSUE website, http://www.msue.msu.edu/vanburen. Clicking on Commercial Fruit will take you to my first page http://www.msue.msu.edu/vanburen/disthort.htm. There are several links at the top of the page to Weather sites, Current Fruit IPM conditions in SW Michigan, and links to other fruit websites. There is a paragraph of text listing the fruits grown in SW Michigan that I work with. All these fruits are linked to specific crop pages with links to online Extension bulletins and articles. The grape page http://www.msue.msu.edu/vanburen/grapeweb.htm has links to MSU Grape bulletins on diseases and pest found in Michigan. There are also links to other web sites including a series of pages on the Michigan Grape Society http://www.msue.msu.edu/vanburen/mgs.htm. We have posted back issues of this newsletter. Information on SW Hort Days, Grape Viticulture Day at SWMREC in July, as well as other information on the Grape Society.

Be sure to check out the links page with links to the weekly MSU fruit IPM newsletter, "The Fruit CAT Alert" at http://www.msue.msu.edu/ipm/fruitCAT.htm. You can also access the MSU "Fruit Spraying Calendar", (E-154) at http://www.msue.msu.edu/epubs/pestpubs/E154/index.htm.

I am really quite proud of the pages I have posted and several pages get over 100 hits a week and the grape pages often lead the way. There are also links to Cornell's grape information that includes their grape newsletters and grape IPM fact-sheets. There are links to other grape resources on the web. The best of these for Michigan and other midwestern grape growers is the Lake Erie Region Grape Program at http://lenewa.netsync.net/public/LERGPhom.htm. From this site you can find lots of Cornell's grape information. Cornell has a lot of information posted on the web. Michigan Indiana and Ohio have coordinated their grape research and Extension efforts to reduce duplication of effort and provide more resources for growers in those states. The Michigan Wine & Grape Industry Council has a website at http://www.michiganwines.com/. Indiana's Wine Council is at http://www.indianawines.org/. Purdue has a weekly pest update Facts for Fancy Fruit http://www.hort.purdue.edu/fff/fff.html. Purdue has also posted the small fruit spray guide for Midwestern states at http://www.hort.purdue.edu/hort/ext/sfg/. Ohio has posted a companion book, "Midwest Small Fruit Pest Management Handbook" at http://www.ag.ohio-state.edu/~sfgnet/. This site also has links to a lot of Ohio's information. Illinois has a good site at http://w3.aces.uiuc.edu/NRES/faculty/Skirvin/cfar/index.htm, focused more on wine grape production. If you want to expand your horizons beyond the Midwest check out the Northwest Berry InfoNet one of the best small fruit sites http://www.orst.edu/dept/infonet/.

During this post-bloom period, many Michigan grape growers are considering whether grape berry moth management is required. In recent weeks, monitoring traps were catching few moths during the cool weather, but the flight increased at some farms once the weather warmed up. In these sites, adult moths have waited to emerge from pupae through the bad weather and are now flying and laying eggs as temperatures have risen above 50^o in recent nights. The recent warm weather means that these eggs will quickly hatch, and young larvae will be emerging and feeding as the flight tails off.

If high populations of larvae are feeding at this time of cluster development, then yield may be impacted. Looking through clusters, both at the edge of the vineyard and inside, can help determine whether an infestation is present. Although, no relationship has been developed between yield and this early cluster feeding by berry moth, effective post-bloom control of grape berry moth in highly infested vineyards can help prevent later damage.

In vineyards where grape berry moth is a recurrent and damaging pest, management of the larvae during the post-bloom period is warranted. Post-bloom, grape berry moth can be effectively controlled with an application of a broad-spectrum insecticide; Guthion, Imidan, Lannate, Sevin, or Danitol are effective products registered for use in grapes. Growers are often targeting leafhoppers with this timing, and so it should be noted that Sevin resistance has been found in grape leafhopper in certain regions of Michigan. Provado is a highly effective product for leafhoppers, but will not affect grape berry moth. Lannate provides good immediate activity against grape berry moth, but has a short residual period of toxicity. Danitol is an effective berry moth product but as a synthetic pyrethroid, it is recommended that its use be limited to only one post-bloom application due to concerns for resistance management and protection of beneficial insects. Finally, Bt. has shown good activity against grape berry moth early in the season when it was applied regularly against the exposed larvae. This product is highly specific to moth larvae and will not harm leafhoppers or beneficial insects.

If an insecticide is used against grape berry moth, good spray coverage is critical to gaining control. Almost all grape berry moth eggs and larvae are on the clusters, and so it is important to use enough water to achieve complete cluster coverage. As the canopy and cluster increases in volume during the year, spray volumes should increase to adjust for this. Later-season egglaying and larvae can be inside the more compact cluster, and so spray deposits must be able to reach into here.

The most important window for deciding if grape berry moth control is required is during mid-late July. At this time, the larvae are developing on growing clusters, and can be counted to determine whether an insecticide is warranted during early August. Sampling at the vineyard border and interior can allow informed decisions about whether to spray the whole vineyard, or whether a border application will be sufficient. This timing provides a long enough period before harvest that control can be gained and pre-harvest intervals are not a constraint. A companion article later this year will review mid-season options for insect control in grapes. Weekly updates are supplied by county extension agents, and are available in the weekly Fruit Crop Advisory Team alert. This is on the internet at http://www.msue.msu.edu/ipm/aboutcat.htm, where you can sign up for email and printed versions.

Dear readers of the Michigan Grape Society Newsletter, I would like to thank you for your continued interest in the Michigan Grape Society. Through your attendance of our various programs and our sponsored program at the Southwest Michigan Hort Show, our Grape Society has continued to show much growth over the past few years. In the past, our organization only put on the Hort Show in February and had a small newsletter. Now, we are responsible for three shows and a quarterly newsletter. This is a result of the growth of the organization.

This growth in the Michigan Grape Society has reached a point where the costs are increasing at a greater rate than the growth. The newsletter was a small publication published sporadically at a cost of $500 per mailing. The newsletter, now published quarterly, now cost $1,500 per newsletter. This happened as a result of our increasing the quality and having the mailing list more than doubled. Our other events, such as the Hort Show and Viticulture Field Day and Steak Cookout are also increasing in cost. Put these increases on top of a new program we are proud to be a part of in Grand Rapids, and the result is clear. We need to generate more income to help maintain and increase the quality and value of the Michigan Grape Society.

The board of directors has looked at all options available and it was decided that we must charge for membership to this organization. The money we charge at our events merely covers the costs incurred by these programs. Now our costs are greater than the money collected at these events. The lunches are now greater than the entry fee at the Hort Show and the cost of Viticulture Field Day steak cookout has increased. The newsletter is costing three times the original costs and we have exhausted our alternatives such as advertising and booth rental. Our booth rentals at these programs have been at or near 100%. These prices have increased as well. We are unable to take the cost out of our administrative affairs due to the fact that all members serve voluntarily with no stipend.

What will the annual membership fee of $20 give you? The benefit of receiving the quarterly newsletter, which will inform you of upcoming events and registrations, disease and insect problems and various other topics. The membership fee will also help with the value and quality of our programs. The Michigan Grape Society newsletter is the only publication that carries the dates and times of our events. We hope this fee will not be an undue burden and we know that you will benefit more than is required for the cost of membership.

If you have any questions or comments please talk with one of the Michigan Grape Society Board Members.

This year most of the grapes fell off the vines about one week after bloom. Cool weather before and during grape bloom delayed bloom by about 10 days and then resulted in a ragged bloom. These conditions lead to poor fertilization of the crop. Some of the vineyards have lost almost all their berries, most show reduction to 10 berries or less per cluster very few vineyards show little or no damage. Often these conditions can be seen in different areas of the same vineyard. Some growers are doubtful the remaining crop was worth spraying and harvesting.

Grapes are a warm weather plant and grow best at temperatures above 50F. Juice grapes such as Concord and Niagara were almost in bloom on May 21. Cool, cloudy weather with average temperatures near 50F followed and warm temperatures did not return until June 8. This cool weather virtually stopped the growth of the vines. On May 21, I thought the grapes were ready to bloom. I thought with the cool weather forecast for the week that they would bloom at the end of the week. They looked the same on May 28, a week later; I looked for and saw no bloom. This cool wet weather affected all the crops grown in our area. Corn was stunted in the fields, insect pests were virtually nonexistent as the weather was to good for insects to be active. Apple growers were unable to apply apple-thinning sprays because it was too cold for these sprays to work.

There was a brief warm period with temperatures in the 60s on May 29-31, when grape bloom began. Bloom was delayed by about 10 days. The delay in bloom by cool conditions probably resulted in some losses but the cool conditions during bloom also resulted in poor pollination. Cool temperatures returned on June 1 with average temperatures at or below 50F. These temperatures again shut down grapevine growth.

The results on the flowers were even more devastating. At temperatures below 60F few flowers opened. Some flowers opened at the base but the cap does not fall off, so the flower cannot be pollinated. In order to set fruit the flower must be pollinated by several pollen grains. Each pollen grain germinates and forms a pollen tube. This pollen tube then grows down an ovary at the base of the flower and fertilizes one of the ovules inside. There are 2 ovaries in the flower and each ovary has 2 ovules so grapes can have 4 seeds. The fertilized ovule now continues growth as the seed in the fruit. Grape berries with 2 or more seeds are likely to say on the plant and grow. Berries with one or no seeds usually fall off. Grape pollen has an optimum temperature of 65F for grape pollen tube growth, below 60F pollen growth is reduced. The pollen grain has enough energy reserves to live about 24 hours after germination. It is doubtful that the pollen fertilized many berries pollinated before June 8 before it died. On June 8, warm weather returned and bloom was almost finished on June 11. Most of clusters had finished blooming, only a few clusters in the vineyards were still in bloom. I was surprised to see as much fruit as I saw. On June 18, it was obvious that we had lost a lot of berries. The unfertilized berries fell off the clusters as warm weather returned and growth of the fertilized fruit began.

Most of the berries fell off the vines in the week after bloom. I would estimate losses at 60% or more across the entire region. Some of the vineyards have lost almost all their berries, most show reduction to 10 berries per cluster (less than third of normal), and a few vineyards show little damage. Often these conditions can be seen in different areas of the same vineyard. An awful lot of this variation is probably due to the timing of the bloom and the local conditions in the vineyard where some vineyards had warmer temperatures in bloom than other vineyards or were delayed in bloom until the warmer weather came.

Some grape growers are now faced with hard questions. Are my grapes worth spraying or can I reduce the amount of sprays to save money? Are they even worth harvesting? I would not recommend any more fertilizer the vines will be too vegetative already with the light fruit set. Insects that feed on the leaves will not be as important as when we have a full

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