- Research Publication -
Cryolite on grapes/Fluoride in wines - A guide for growers and vintners to determine optimum cryolite applications on grapevines
by
Gwynn Sawyer Ostrom
CATI Publication #960601
© Copyright June 1996, all rights reserved
INTRODUCTION
This pamphlet is designed to help growers and vintners determine optimum Cryolite applications. Over the past six years, there has been concern about fluoride levels in wines, which has been linked to Cryolite use in the vineyard. A wine fluoride limit set by the European organization O.I.V. has forced wineries to reevaluate their winemaking procedures and growers to reassess their vineyard practices to produce exportable wines that meet the limitation.
A 3 part-per-million (ppm) fluoride limit currently exists for U.S. wines exported to European Economic Community (E.E.C.) countries. Fluoride is a common element that comes from soils and water. It also comes from other sources, such as chemical inputs. Chemicals that can affect fluoride in wines have been scrutinized because they are the easiest to identify, isolate, and therefore control. Research at California State University, Fresno has shown that certain applications of Cryolite can significantly increase the amount of fluoride in wines.
The information provided in this pamphlet describes the relationship between Cryolite and fluoride. A chart is included as a tool to help growers and wineries predict fluoride levels based on Cryolite application rates and timing.
THE PROBLEM
In 1989, the O.I.V. decreased the tolerance of fluoride from 3 ppm to 1 ppm in wines exported to E.E.C. countries. Negotiations between the U.S. and O.I.V. resulted in an agreement that the tolerance would be reconsidered if research substantiated its reinstatement to 3 ppm. A final decision by the O.I.V. was to be made in 1996.
Cryolite, with an active ingredient of sodium alumnofluoraminate, is an insecticide used primarily in the San Joaquin Valley to control western grapeleaf skeletonizer, omnivorous leaf roller, and orange tortrix. Fluoride is part of Cryolite's active ingredient. Cryolite applications were thought to cause increased fluoride levels, which led to wines with unacceptable levels of fluoride for export. In addition, high fluoride levels in must can lead to winemaking difficulties, such as stuck fermentations and undesirable flavors and other aroma characteristics.
From 1990 through 1994, California State University, Fresno researchers studied Cryolite application rates and their timing to observe the effect on fluoride in wines. This five-year study contains data on hand- and machine-harvested grapes, including red and white varieties, from vineyards throughout the San Joaquin Valley.
THE SOLUTION
Our research has concluded that, depending upon timing and rate, Cryolite does have an effect on the level of fluoride in wines. Machine harvesting does not appear to affect fluoride content. 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 and minimize fluoride residues.
The following chart shows rates, timings, varieties, and fluoride ranges expected from specific applications. Thechart is listed by rate (in pounds active ingredient (a.i.) per acre) and timing of 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.
The chart shows specific rates and timings along the left side, and fluoride in ppm at the top and bottom. How to use the chart:1) Determine the desired rate and timing
For example, if the target spray program is 6 pounds at bloom, find the 6 lb bloom section on the left-hand side of the chart. Working from left to right in that section, locate the bars associated with the 6 lb bloom rate. Find the grape variety in question, and follow along the top or bottom scale to determine the fluoride range for that variety. In our tests, spraying Zinfandel at the 6 lb bloom rate produced wines with fluoride levels of 0.4 to 1.2 ppm. A 6 lb bloom application of Cryolite on Barbera produced wine fluoride levels of 0.1 to 1.4 ppm.
2) Identify that spray program on the chart, and
3) Read across left to right in that section to see the predicted fluoride range for a specific variety.
If the variety to be sprayed is not listed for a chosen spray schedule, use the example shown on the chart for that specific rate and timing to get a general idea of fluoride levels. Red wine varieties may produce higher levels of fluoride than white wine varieties because of extended skin contact time during the winemaking process.
It is important to recognize that there will be some low level of fluoride in wines, even in wines made from grapes that were not treated with Cryolite. Research at California State University, Fresno has shown that fluoride levels in wine produced from grapes not treated with Cryolite can range from 0.1 to 1.6 ppm, depending upon location and variety.
Cryolite manufacturers and wineries currently recommend a 6 pound prebloom application. This rate and timing appear to produce levels well below 3 ppm fluoride, and control of insects is adequate. If additional insect control is needed, Bacillus thurengensis (B.t.) products should be applied.
As long as the O.I.V. allows a 3 ppm limit, most growers and vintners should have acceptable fluoride control with Cryolite applications of 6 pounds per acre at or before bloom. According to our research, a 6 pound prebloom or bloom application produces wine with fluoride levels well within the 3 ppm O.I.V.-accepted range. An 8 pound bloom rate causes fluoride levels to approach 3 ppm, so it should be considered with caution. Although the maximum allowable label rate per year is 20 pounds ai/acre, we do not advise exceeding bloom or prebloom rates, or making multiple applications. Insect control may be improved, but wine fluoride levels will rise above the 3 ppm limit.
The grower and vintner should work out a mutually acceptable spray schedule to insure good insect control and to minimize wine fluoride. The chart can help estimate fluoride levels based on Cryolite application rates and timing.
ACKNOWLEDGEMENTS
I would like to thank the following individuals and organizations for their financial and personal assistance. This research could not have been completed without the help of Roy Whitson, Elf-AtoChem; Dick Messinger and Gary Sullivan, Gowan Company; American Vineyard Foundation; California Agricultural Technology Institute; Lou Quaccia, Morris Ball, and Frank Rodriguez at Vineyard Properties/Wine Group; Phil Bava, Art Caputi, Stan Grant, and Mark Fahey at E&J Gallo Winery; Jerry Lund at Lund Farms; Keith Striegler, Mark Salwasser and Alex Davis at California State University, Fresno; Ray Jacobsen and Don Laub at J&L Vineyards; John Simpson, Ben Casey and Jack Morris at Simpson Vineyards; and Kevin Andrew and David Fenn at SunWorld.
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Copyright © 1996. All rights reserved.
CALIFORNIA AGRICULTURAL TECHNOLOGY INSTITUTE - CATI
College of Agricultural Sciences and Technology
California State University, Fresno
