by Jackie Dresser
JAMESTOWN, NY — According to Cornell Cooperative Extension Chautauqua County’s Lake Erie Regional Grape Program, Growing grapes in the Lake Erie region is not for the faint of heart. While growing regions like Napa Valley may enjoy warm and dry growing seasons with plenty of sunshine and “winters” where 40°F is considered frigid, the Lake Erie region is no stranger to negative winter temperatures, spring frosts and sporadic sunshine making it more difficult for growers to ripen fruit here compared with warmer growing regions. With Mother Nature setting some strict house rules, growers here are always under pressure to adapt. So how do climatic conditions influence vineyard management in the Lake Erie Region?
A dormant vine is pruned during the winter and is the grower’s first chance to set the crop potential for the following season. The more buds a vine has going into a growing season, the more fruit there will be on that vine. Since growing seasons here don’t have limitless sunshine, there is a limit to the fruit that each vine will ripen. Growers seek to maximize the amount of fruit on a vine but are risking unripe fruit at harvest if they leave too much on each vine. The other major risk is spring frost. If a grower prunes to the desired final bud number during the winter, there is a chance that spring frost will result in bud damage and wipe out some of that crop potential before bloom even occurs. So, there is always a bit of a gamble at play with manipulating crop potential over the winter.
Lake Erie grape growers tend to prune conservatively, leaving more buds than desired, a little insurance against spring frost damaging fragile buds. In early spring, buds swell and eventually burst, allowing the first leaves to emerge along shoots. When the shoots are two to five inches long, the Lake Erie Regional Grape Program (LERGP) team is off and running. The first thing we do is to measure the growth of these new shoots. We deploy spectral reflectance sensors (NDVI) to scan vineyards for much more than the naked eye can detect. These sensors are sensitive enough to pick up even slight variation in vegetative growth.
We combine data from these sensors with manual sampling to generate shoot count maps. Since more shoots equals more potential crop, this information is crucial for growers to know. Every vineyard is different and most growers have a good idea of how many shoots a vine can handle, so the idea is to go out and thin some of the shoots off in a vineyard to set the crop level within the range of what will ripen. The trouble is, this range can vary within a vineyard; bigger, stronger vines can ripen more fruit than smaller weaker vines. This is where the Lake Erie Regional Grape Program (LERGP) team comes in.
LERGP researchers at the Cornell Lake Erie Research and Extension Laboratory (CLEREL) implemented a commercial scale variable rate shoot thinning trial this spring. Three blocks were chosen for study, two on each end of the Lake Erie grape belt and one in the center of it. Shoot count maps were generated for each vineyard and each vineyard was split into management classes based on the observed variability in shoot number. The LERGP team worked with growers to develop a management plan in each class, setting a desired target for shoot number after thinning. A digital map of the management classes was fed into a field computer that controlled the rate of the shoot thinner, taking off more shoots in areas with high shoot counts and less in areas of lower shoot counts. All the operator had to do was drive, and the variable rate equipment adjusted itself to the needs of each area of the vineyard. Stay tuned as we monitor the growth of the vineyards this season, the ripening rate of fruit in thinned vs. un-thinned areas of each vineyard and map the yield at harvest. For more information on variable rate shoot thinning and much more, visit lergp.com and efficientvineyard.com .
The Lake Erie Regional Grape Program is a cooperative effort between Cornell and Penn State Universities; the participating Cornell Cooperative Extension Associations of Chautauqua, Erie, Niagara and Cattaraugus Counties in New York and Erie County in Pennsylvania; and participating industry partners National Grape Cooperative (Welch’s), Constellation Brands and Walkers Fruit Basket. The LERGP extension team provides research-based educational programming for commercial grape growers throughout the year at venues across the Lake Erie grape belt. For more information on LERGP, call 716-792-2800 or visit our website at http://lergp.cce.cornell.edu/ .
For more information, call 716-664-9502 or visit our website at www.cce.cornell.edu/chautauqua . Cornell University Cooperative Extension provides equal program and employment opportunities.
Smarter shoot thinning; the Lake Erie Regional Grape Program implements variable rate shoot thinning in three commercial concord vineyards
by Jackie Dresser