Dr. Wayne Wilcox will be presenting two sessions at the Southwest Hort Days, February 8th, 2001. The first session he will speak about disease control in grapevines, including the most current information on fungicide choices. The second session will be a discussion on Phomopsis Cane and Leaf Spot.

Dr. Terry Bates, is a Western, New York native, growing up in Rochester and receiving his undergraduate degree in Biology form St. John Fisher College. After college, Terry moved to Penn State where he completed both a M.S. degree in Horticulture and a Ph.D. in Plant Physiology. While at Penn State, his concentration was in the area of root biology and plant nutrition. In 1988, Cornell hired Terry to be the viticulturist for the Lake Erie Grape Program in Fredonia, New York.

This trade and educational show is sponsored by the Michigan Grape Society, Peach Sponsors and Southwest Michigan Growers and coordinated by Michigan State University Extension.

If you would like to be an Exhibitor or a Contributing Sponsor please call Jerri Pursley at 616-657-7745 and she will get you the necessary forms. If you are a Contributing Sponsor of $50 or more we will add your name to our display banner.

In a previous issue of this newsletter I discussed possible reasons why portions of many of Southwest Michigan juice grape vineyards set poor crops in 2000 despite the overall record crop year. Naturally, by the time that condition was discovered during the growing season it was too late to take steps for the current year's production. But now that it's winter time, there are vine management strategies that can often help to increase vine productivity.

First, the vineyard condition we are about to discuss is one where vines are vigorous with abundant shoot growth. At this time of year the vines appear to have lots of new wood, often with large so-called bull canes that may have lateral canes on them. These are vines that produce lots of vegetative growth but little crop. Although, conditions like boron deficiency or virus infection can cause poor cropping of vines, these are uncommon. The more likely reason for poor cropping of vines is relating to the conditions that influence the development of fruitfulness in nodes (buds). Nodes develop their fruitfulness in relation to how well they and the leaves on the shoots by them were exposed to sunlight during the previous growing season. When vines produce excessive shoot growth, often the nodes at the base of shoots develop in dense shade. If the pruning strategy involves retaining short canes (4-5 nodes), a grower is likely to have many nodes that produce fruitless shoots or no shoots at all. Ironically, further out on such shoots the leaves and nodes often have " climbed " into the sunlight, and therefore, have developed more fruitfulness that those at the base (Fig. 1). Repeating pruning cycles with short canes will just cause this condition to repeat itself year after year. One way to break this cycle is to prune to long, even very long canes, so that fruitful nodes are retained on the vine so they can produce a crop. In these situations node fruitfulness will often increase around node 7 (Fig. 1) but in some canes it may not increase until node 10 or more on the cane (Fig. 2). Therefore, pruning to long canes and tying them as best as possible down and away from the top wire cordon will help increase the crop level. When pruning bull canes which have lateral canes on them, it is critically important to prune to save nodes on those laterals either as 1-2 spurs along the bull cane or as long canes themselves because nodes on laterals are the highly fruitful nodes the pruner is seeking to save on the vine.

Increasing the crop level in this way may be all that is needed to reduce excess vigor and vine size. However, if the vines are very large, then additional vine devigorating practices should be employed such as reducing or eliminating nitrogen fertilization and maintaining a competitive sod in the row middles. I do not recommend reducing weed control under the trellis because it may be difficult to reestablish weed control later and weeds under the trellis can nurture vine disease problems.

Of course, pruning to long canes is a nuisance for those accustom to short cane pruning along a top wire cordon. To be able to return to short canes in future years a grower should shoot position vines next growing season so the zone around the cordon is exposed to sunlight, which will promote node fruitfulness on the basal nodes of canes attached to the cordon.

There are extreme cases when vines on heavily organic soils (such as in a lowland frost pocket) remain excessively large and unmanageable, even when they are not nitrogen fertilized and are kept with permanent sod row middles. Under those special conditions the seemingly radical approach of removing alternate vines may be the only way to get vine size and productivity into balance.