Click here to go to Dr. Terry Bates Home Page
Click here to go to the Lake Erie Regional Grape Program Current Crop Update
Click here to go to the Lake Erie Regional Grape Program Home Page
click here to go directly to the 2/1/2001 addendum section
I was very happy to see the number of growers at the mechanized pruning demonstration at the Betts Vineyard last week. It reflects both the need and the interest in the subject.
Mechanical pruning research is not new to Western, New York. Pollock, Shepardson, Shaulis, and Crowe published a paper in 1977 on mechanically pruning Concord vineyards. The research was started in 1969 and references are made to preliminary research being done in 1957. Although many growers associate mechanical pruning research with minimal pruning research done in the 1980s and 1990s, the 1977 paper has both similarities and differences to the Betts pruning system seen last week (a far cry from minimal pruning).
1977 vs. 2001: The Similarities
For ease of reading, I will refer to the 1977 research as the Shaulis system and I will refer to the 2001 research as the Betts system.
Both the Shaulis and Betts systems use mechanical pruning with hand follow up to reduce the bud number to something similar to a hand pruned vineyard. After aggressive mechanical pruning, the Shaulis system uses both cane thinning and shoot removal for both quality bud selection and bud number reduction. Cane thinning is very similar to what we generically call hand follow up in the Betts system. In the 1970s, shoot removal was the mechanical or chemical removal of additional shoots on the top of the cordon - a practice not used today.
1977 vs. 2001: The Differences
The major differences between the Shaulis and the Betts systems are in the location of the retained nodes and shoot positioning.
The Shaulis system uses lower 180 pruning. Meaning, canes and buds are only retained below the cordon and any shoots originating on the top of the cordon are scrubbed off. Retained shoots are then shoot positioned downward near bloom and 15-20 days after bloom. For the first few years, this system cuts off the exposed sun wood and the shoot positioning eliminates any shoots running parallel with the cordon (a.k.a. buggy whips or runners) that may shade other shoots. If lower 180 pruning is maintained, eventually all the wood (sun and shade) is below the cordon. With shoot positioning, the renewal wood directly below the cordon is attached to the most sun exposed leaves. Therefore, the most ripe wood is right where you want it for the next season.
In the Betts system, pruning is flipped upside down, where retained canes and buds are from the top of the cordon. Rubber, plastic, or metal fingers pull the sun wood up in the air, cutter bars prune the canes to a desired length (5-8 buds), and a second set of cutter bars prune the shade wood out of the system. Runners are prevented by the direction and aggressiveness of the fingers. When the fingers pull the wood down, runners may be supported by the cordon or wire and may not get cut. A manual vine separation cut may be needed to take care of the runners in this situation. When the fingers pull the canes up in the air and when they are aggressive, runners are more likely to be caught and pruned.
To shoot position or not to shoot position? That is the question.
Shoot positioning used to be a big part of Shaulis research program in Fredonia despite the pruning method. However, it is rarely used today in commercial vineyards and the question of shoot positioning continues to come up.
To find the answer, I think we have to look at the environment in which shoot positioning of Concord was developed and its intended use. Much of Shaulis research was conducted at the Fredonia lab with balanced pruning - a situation of a good site, intensive management, and conservative pruning. The result? Ripe crops and vines that grow to the moon (3 pounds of dormant cane pruning weight per vine or better)! Excessive vegetative growth causes shade within the canopy, especially in the renewal zone. Shoot positioning was developed to suppress vegetative growth and increase sun exposure to the leaves that most directly ripen the wood of the renewal zone. Long-term research shows that shoot positioning does not necessarily increase vine yield at a given bud number (i.e. 70 node shoot positioned vines and 70 node not shoot positioned vines have the same yield). However, shoot positioning does put the ripe buds in a position for easy pruning.
Lets back up! How many vineyards in the Lake Erie Belt are suffering from excessive vegetative growth and major shade problems? Natural restrictions such as soil water holding capacity and soil pH as well as management problems such as poor weed control and poor pest management decrease vine growth on a production level. Furthermore, if the vineyard is managed well and excessive vine size is achieved, we tend to hang larger crops. Crop stress in itself will reduce vegetative growth.
My opinion of shoot positioning? It has its uses in situations of excessive vine growth and shaded canopies. It brings ripe nodes back to the cordon where otherwise the ripe buds would be out on the end of long inferior canes. I would not use shoot positioning in situations of moderate, healthy, well-exposed canopies. We manipulate the natural growth habit of Concord grapevines enough by putting them on a trellis and pruning them to a desired bud number. Shoot positioning in situations where it is not needed defeats the natural tendency for shoots and leaves to find and compete for their own sunlight.
I hope to see you all at the grape growers conference on the 10th!
2/1/2001 ADDENDUM:
SOME QUICK COMMENTS: by Dr. Terry Bates
As a researcher, I spend much of the winter in front of the computer cranking out data analysis from the growing season. I leave it up to the extension agent to tell me what is going on in the field. Unfortunately, we are out of an agent at this point. Bob Betts drove me around some vineyards this morning and I would like to make some quick comments on some observations.
There were many vineyards leaving up plenty of buds. Maybe too many! For those of you that know me, I am all for leaving up enough buds for a decent crop but we MUST be careful about that decision.
Let's look at the current situation of bud number and bud quality. Because of a moderate crop and plenty of water in 2000, there is plenty of ripe wood to choose from in most vineyards. Exceptions may be the vineyards that were waterlogged last spring, had retarded shoot growth early, and were behind the eight ball the rest of the season. According to Martin Goffinet, cool cloudy weather after bloom in 2000 decreased the quality of the buds for 2001. So, we have plenty of buds of average potential.
What is the 'X' factor? Fruit set! In 2000, ripe nodes of periderm (buds) were low, bud quality was high, and fruit set was 'blah.' Growers that left up too few buds because the bud quality was high were greatly disappointed. Growers that left up plenty of buds ended up with a decent crop that did not need to be thinned. If fruit set had been good, there would have been plenty of vineyards to thin or they would had suffered from overcrop. At this point, we have no way of predicting fruit set and we may never know how to predict fruit set.
In 2001, ripe nodes of periderm are high and bud quality is low. Fruit set is the big question mark. Lets look at some options. If you are willing to thin, go ahead and leave up a few extra buds. We may have fewer clusters per vine in the spring but if all those clusters set well, overcrop is the risk and thinning will be the answer. If fruit set is average to poor, then you should be in good shape. If you are not willing to thin, the smart choice would be to stick on the conservative side. The risk here is that fruit set will be poor and the crop will be less than you want it to be. However, you take overcrop out of the equation and you will most likely have plenty of vine growth and ripe wood for 2002.
Do we know everything we need to know about thinning? No! We do know that mechanical thinning 30 days after bloom can reduce crop, increase juice soluble solids, and (most importantly) increase the amount and quality of ripe buds for the next season. Thinning accuracy and vineyard variation are two issues that we are still investigating and trying to improve.
My fear: Those of you that are leaving up 120 buds or more are not willing thin in the case of an overcrop. Yes, I know that many of you are talented at the art of field blending but you must also think about the health of the overcropped vines for the next season. At the Fredonia lab (a good site with intensive management) we only leave 120 buds per vine in blocks where we are willing to thin or on control vines of thinning experiments. Blocks that do not get thinned are pruned to 100 buds OR LESS. Although I cannot tell you what bud number to prune your vineyard to, I hope that these comments with the knowledge of your own vineyard will help in your winter decisions. Good luck with pruning and I will start planning my next thinning experiments!