- Summer 1996 "Update" Newsletter Article -
Cryolite guide to aid growers, vinters
From CATI Publication #960701
Copyright © 1996. All rights reserved.
A special guide to help growers, vinters and crop care consultants predict fluoride levels in wine will be available this month from the the California Agricultural Technology Institute (CATI).
Research associate Gwynn Sawyer Ostrom has compiled four years of research data on cryolite use in vineyards into a format that shows fluoride levels in wines made from the treated grapes.
Cryolite is an effective insecticide used in California to control western grapeleaf skeletonizer, omnivorous leaf roller, and orange tortrix. Since fluoride is part of cryolite's active ingredient, cryolite applications have been linked to the increased fluoride levels in wine. Depending on timing and amount of cryolite application, fluoride levels in wine can range from one to 12 or more parts per million (ppm).
Fluoride in wine was not a serious trade issue until 1989 when the O.I.V., a key European trade organization, established one ppm as the maximum allowable level in wine imported by the European Economic Community (EEC). Intense negotiations between U.S. and European trade representatives resulted in the tolerance level being raised back up to its prior level of three ppm. But that move is subject to change again, possibly this year.
In an effort to help growers and vintners more accurately predict fluoride residues, Sawyer Ostrom began a five-year series of studies that included a variety of cryolite application rates and timings. The results contain data on wine from hand- and machine-harvested grapes, including red and white varieties, from vineyards throughout the San Joaquin Valley.
"Our research has concluded that, depending upon timing and rate, cryolite does have an effect on the level of fluoride in wines," Sawyer Ostrom said. "Multiple applications of cryolite during the growing season significantly increase fluoride in wines. Therefore, cryolite application rate and timing are critical to ensure adequate insect control in the vineyard and minimal fluoride residues in wines."
Depending on rate and timing of cryolite application, flouride levels in wine can range anywhere from one to 12 ppm. The higher levels can lead to winemaking difficulties, such as stuck fermentations, or can result in undesirable flavors or aroma characteristics in finished wine, Sawyer Ostrom noted.
The information in the pamphlet shows rates, timings, varieties, and fluoride ranges expected from specific applications. No matter what the specific cryolite application, fluoride levels may vary from year to year and from location to location, depending on the applicator, the amount of rainfall, other vineyard applications, and the local water and soil conditions. Nevertheless, the chart predicts fluoride levels that serve as a starting point in estimating fluoride in a specific vineyard.
"The vineyard manager and winemaker should look at each case individually, and ideally, monitor fluoride levels over several years to determine an average expected fluoride level for that specific vineyard," Sawyer Ostrom said.
The pamphlet is entitled "Cryolite on grapes/Fluoride in wines." To request a copy, see the Publications available form on Page 7.{ page top }