Deleafers: another tool to fight disease and manage grape maturity

Deleafers have come a long way. The objective is to prevent leaves from shading grape bunches so that they mature with appropriate brix levels. According to Niagara-on-the-Lake grape grower, Kevin Watson, deleafers are an extremely important tool to achieve harvest quality under differing climatic conditions.

“Put it this way, we buy a lot of grapes and we wouldn’t consider buying a red vinifera grape if it wasn’t deleafed in a timely way.”

The technology has improved over recent years. A decade ago, a deleafer acted like a lawn mower, tearing complete leaves off the vine and in some cases bits of the cane. This was a very aggressive approach.The advent of rollers was an improvement, but again, some of the tiny grapes would be caught up in the process. Today, deleafers are more sophisticated, shooting air through the leaves.

An air compressor powered by a hydraulic motor shoots out air like popcorn. The effect is that holes are blown through the leaf so that only the veins remain. The result is that the remainder of the leaf dries up and falls off. The cane does not overcompensate by growing new leaves. 

As Watson explains, by the time that leaves are two months old, they shade the maturing grapes too much. Removing these leaves, just after bloom and before bunch closure, and then again at veraison, opens the grapes to more sunlight. Another advantage is that grapes are less prone to disease exposure such as molds and mildews. Opening the canopy minimizes botrytis.

Deploying a deleafer can make a big difference in harvest quality. Watson reports an increase of one to two points in brix levels of grapes which have undergone deleafing compared to those without deleafing. With extreme weather patterns and uncertain harvest schedules from year to year, earlier maturation translates to money in the bank when selling to wineries. An increase in brix usually means that acidity levels have decreased. 

“I’ve known other growers who had grapes rejected due to high acidity,” says Watson. “In cooler years, it’s important to achieve the taste profile and to get the crop harvested as soon as possible.”

What was once a pioneering practice is now commonplace among grape growers, albeit with more sophisticated equipment.

Photo 1: Joe Pillitteri, Lakeview Vineyard Equipment Inc., is one of the purveyors of grape deleafers, who exhibits at the Ontario Fruit and Vegetable Convention. Photo Denis Cahill.

Put it this way, we buy a lot of grapes and we wouldn’t consider buying a red vinifera grape if it wasn’t deleafed in a timely way.

~ Kevin Watson

Key word:  Deleafers, Kevin Watson, Lakeview Vineyard Equipment Inc., grapes – LATEST NEWS 

Publish date: 
Monday, February 1, 2016

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