Southwest Michigan Horticultural Days February 4th and 5th, 2004, held at Lake Michigan College was again attended by over 400 participants. We had new and returning exhibitors which filled the exhibition room.

The featured out-of-state speaker Dr. Wayne Wilcox, Cornell University, gave two presentations covering “Powdery Mildew and Phomopsis” and the “Mode of Action of Grape Fungicides”. Dr. Art Agnello, Cornell University, and Dr. David Ferree, Ohio State University, were also featured out-of-state speakers. The quality programming and exhibitors continues to draw a good attendance.

The Wine Hospitality Reception featured wines from local wineries and was well attended by exhibitors, speakers and participants.

The Michigan Grape Society would like to thank all the exhibitors, wineries who donated wine for the reception and all the participants for making Hort Days successful.

By: Rufus Isaacs, MSU Grape Entomologist

It would be nice if our problems with the huge 2003 juice grape crop had ended last fall when we put the harvesters away in the barns. Unfortunately, the stress of that large crop on our vines will be with us in the 2004 growing season. Pruning weight data from our experiments document a sharp decline in the size of vines due to this large crop. We also know that large crops, which are harvested late, result in fewer carbohydrate reserves in the vines. Those reserves are especially important in the early growth of the vines so we may well see uneven, erratic growth patterns at the start of growth. Reduced vine size translates to reduced capacity of vines to bear and ripen fruit. Therefore, in many vineyards 2004 should be a time to rebuild vines so they are capable of bearing large crops.

To stimulate vine growth the first priority is weed control under the trellis. Without good weed control, no other efforts will promote large vine size. With good weed control under the trellis, the second order of priority for stimulating vine size is vine nitrogen nutrition. Recent research at the Southwest Michigan Research and Extension Center by Mr. Randall Vos, a Hawkeye from Iowa who infiltrated the Spartan ranks, lends some insight into vine nitrogen fertilization practices. His research indicates that budbreak applications of nitrogen were much less efficient in their uptake into vines than those made at bloom or even six weeks after bloom. Therefore, growers should delay nitrogen applications well beyond budbreak to allow for more efficient fertilizer uptake. I’ve observed several instances over the years where weather patterns have had a dramatic impact on fruit set. The stimulation of rapid shoot growth through bloom with nitrogen fertilization could also reduce fruit set. However, over the past 30 years I have observed only two instances where a lack of fruit set could be directly attributed to excess nitrogen levels. Both occurred because large quantities of fresh manure were applied to a vineyard because it was close to the barn from which the manure came! Where vines have been severely pruned or there is a low percentage of buds that push shoots, excess shoot growth stimulation with nitrogen could be a real problem. However, it is highly unlikely that moderate amounts of nitrogen fertilization would impact fruit set on vines with large numbers of shoots. A current experiment in a Berrien County vineyard involves multiple post-bloom applications of nitrogen fertilizer to determine their influence on vine size. Despite an 11-ton per acre crop on these vines in 2003, we were amazed that these fertilizer applications increased cane pruning weights by 60% from approximately 1.5 to 2.5 pounds per vine. These results suggest post-bloom nitrogen could significantly help rebuild vine size in 2004. Although a single post-bloom application of N is unlikely to produce the large response we observed, it should help.

I was reminded by growers at a meeting recently that post-bloom applications of nitrogen are complicated by the volatility of fertilizers like urea or liquid 28. At 75^oF and a soil pH of 6.0, there will be about an 18% loss of N from urea after sitting on the soil surface for 10 days. The rate of volatilization decreases as temperatures and soil pH declines. Incorporation in the soil is impossible for grape growers. However, Mike Staton, MSU Field Crops Agent, tells me that applying liquid 28 in a concentrated band under the trellis rather than in a broad spray pattern can help reduce volatility. There are also adjuvants that can be blended with urea to reduce volatility.

A third strategy for rebuilding vine size is the management of row middles. Viticultural research documents that sod or weed row middles have a depressing affect on vine size. Vineyard blocks that are plagued with small vine size could benefit from row middle management involving either cultivation or herbicide spraying. We have low-volume, row-middle herbicide sprayers at SWMREC that are available for use by growers. Call Diane Dings at 269-944-1477 x 200 to get details on the use of this equipment.

I was asked to write a short review of the Michigan Grape crop over the last three years. Weather conditions in 2001 and 2002 reduced our crop to half of the normal crop. In 2003 the vines tried to carry two years worth of fruit, so in 2004 we are farming weaker vines.

2001- Cool conditions during bloom and we set half crop on Concord. I thought it was poor pollination or poor pollen tube growth. Stan and Terry Bates at Fredonia believe that warm conditions after bloom allowed shoot growth to out compete fruit growth. That explanation makes sense to me also, probably both. There were some vineyards that were little affected. We harvested half crop. The vines went into the winter in good shape.

2002- Early Spring, warm weather in Early April followed by hard frost after bud burst (April 23). This killed the primary buds. Weather was so cool afterwards, that we saw little growth for weeks. Because of the light crop in 2001 the secondaries were very fruitful. I thought the secondary were dead also but secondaries came on fine and we had about 2/3 crop. Because of poor spraying before bloom Phomopsis was a real problem and there was major fruit loss to phomopsis preharvest drop and heavy berry moth flight before harvest. We harvested a half crop. Again the vines went into the winter in good shape from a light crop. I learned to never predict a crop failure until you are sure the secondaries are dead.

As the weather warms, grapevines aren’t the only things preparing to grow in your vineyards. Phomopsis viticola, the causal pathogen of Phomopsis cane and leaf spot, is also ready to strike. Wet weather in early spring causes a release of spores from fruiting bodies on infected canes which are splashed to young, susceptible tissue. Figure 1 shows the number of Phomopsis spores caught per week in rain traps in a Niagara vineyard in Lawton, MI, in 2003. We can see that a peak in spore release occurred in late April/early May, concurrent with a high level of rainfall. Later on, the numbers of spores released were much lower despite high rainfall in July.

Figure 1. Seasonal Phomopsis spore release pattern in a ‘Niagara’ vineyard in Lawton, MI, in 2003. The number of spores caught per week is represented by the red bars, and the total rainfall for each week is represented by the blue line (graph prepared by Brian Lehman).

This graph demonstrates the importance of early fungicide treatments, possibly as early as bud burst, to help get a jump on controlling the disease. In addition to a regular fungicide program, applying a dormant application of fungicide could help reduce the amount of inoculum that is available for infection, and consequently reduce the amount of disease present in the vineyard throughout the year.

Dormant applications are typically applied in the fall or early spring when no green tissue is present on the vines. The purpose of the dormant application is to eradicate pathogens that are overwintering on or just below the surface of the canes. Historically, most dormant sprays have included either sulfur or copper as the primary active ingredient. Lime sulfur, a mixture of calcium polysulfides formed by boiling slaked lime with sulfur, was and still is one of the more popular dormant sprays. Lime sulfur kills mainly through direct contact so thorough coverage is important. Lime sulfur, while effective, does have some negative properties that should be taken into consideration. It is smelly (your neighbors may start to like you less), corrosive, and has a tendency to stain equipment. Lime sulfur is also phytotoxic on green tissue, restricting its use to dormant applications. Another concern with lime sulfur is the price tag. At a rate of 10 gallons of product, we estimate the cost to be between 30 to 50 dollars per acre, depending on the quantity purchased. The non-selective activity of lime sulfur may also knock back other pathogenic fungi like powdery mildew and black rot and insects/mites that are overwintering in your vineyard.

Last year, we looked at the potential for several dormant fungicide applications as alternatives to lime sulfur. The trial was conducted at the Clarksville Horticultural Research Station on ‘Seyval’ vines. Microfine Sulfur at 10 lb/A, Lime Sulfur at 10 gal/A, JMS Stylet Oil at 2% v/v, Kocide (copper hydroxide) at 1.5 lb/A, Topsin M 70WSP (a benzimidazole product) at 1 lb/A, and Microfine Sulfur w/ JMS Stylet Oil at 10 lb/A, 2% v/v were applied at early budswell.

Figure 2. Efficacy of dormant fungicide treatments in reducing Phomopsis rachis infection on ‘Seyval’ grapevines. The % rachis area infected is shown for each treatment as a blue bar. Estimated price per acre for each treatment is also given in the graph.

The biggest indicator of economic loss due to the disease is the amount of rachis infection. Using that to judge the efficacy of the treatments (Figure 2), we find that all treatments significantly reduced the amount of disease when compared to the untreated control. Kocide, JMS Stylet oil, Microfine Sulfur and lime sulfur had approximately the same level of disease reduction with the Topsin M treatment performing best. The Microfine Sulfur with JMS Stylet Oil, while better than the untreated control, had a reduced efficacy when compared to the other treatments. This reduction in efficacy may be due to a prevention in sulfur volatilization and uptake by the fungus caused by the JMS Stylet Oil. When considering the cost of application, the Kocide and the Microfine Sulfur were the least expensive to apply with the Stylet Oil and Topsin M slightly more expensive. While Lime Sulfur was one of the more effective treatments, it was also the most expensive in this case. It is important to note that only the various copper fungicides and Lime Sulfur explicitly mention dormant applications on their labels, while the others are ambiguous or do not mention dormant use at this time. Do not use lime sulfur or sulfur products on sulfur-sensitive varieties such as ‘Concord’ when green tissue is visible, as injury may result.

American Society of Enology and Viticulture, Eastern Section Meeting. July 14- 16, 2004. Roanoke Virginia. www.nyaes.cornell.edu/fst/asev/

Michigan State Fair Wine Competition, East Lansing, MI July 23 – deadline for entry forms July 14 to Council office – entry information will be mailed to wineries in May.  Evening reception follows the competition at the Kellogg Center.

New Michigan Wine Related Websites

www.grapes.msu.edu Central source for MSU information on grapes, including pest management, cultural practices, ordering information for Extension publications and much more.

www.michigan.gov/wineresources Catalog of resource material from vineyard management to winery design, licensing, sales and marketing and financial management. A 16 page Start-Up Guide to Michigan’s wine industry may be downloaded from the site using Adobe Acrobat.

www.wineamerica.org/winedata/winedata.htm Information on the wine industry in each of the 50 U.S. states.

MSU Product Center for Agriculture and Natural Resources

Michigan State University (MSU) was recently awarded $1 million by USDA to establish a center to assist entrepreneurs in starting or improving viable agricultural-based businesses. A client services office has been established just east of the campus, in an office complex with plenty of free parking. Some of the services that the center can offer its clients include:

assisting new and existing entrepreneurs with new business ideas (can be product or service based)
conducting marketing research, including market assessments

assisting in the development of business plans
MSU Extension, Michigan Department of Agriculture and county economic development staff are among those who have been trained as "Innovation Counselors" for the center, developing the skills necessary to assist clients in these areas. Twenty clients are currently working with the Center on project concepts. A fee structure will soon be established, for services requested in the the three phase business/product development process.

The Michigan Grape and Wine Industry Council will be meeting with leaders of the MSU Product Center in April to identify areas of support to meet the needs to Michigan's rapidly growing wine industry.  Individual wineries are also invited to contact the Center to assist them with specific projects.

Spring frosts concern growers anxious to start a new growing season. I have an old MSU publication that lists the probability of a frost for some weather stations in our region. I have extracted a partial table showing the probability of 28F sub freezing temperatures for the local sites. I choose 28 F because this is the temperature that will kill grape tissue after bud burst. The table below is arranged from North to South. Sites located away from Lake Michigan show the approximate distance to the lake. Sites near Lake Michigan show no distance. In the table 10% means that one year in ten, a freeze will occur on or after that date in the Spring.