Technology can forecast vineyard disease

Dan Clarke

In another era, growers shared information around the cracker barrel. While that willingness to share is a characteristic still found in today’s farmers, the quality of their information is becoming much more valuable.

For the last two years, Napa County grape growers have had the advantage of access to portable, solar-powered weather stations. These stations, developed by Adcon Telemetry, forward information from the vineyard every 15 minutes via radio signals to a base station at the University of California Extension office in the city of Napa.

The weather stations can send their data via radio telemetry directly up to 12 miles or, if the distance to the base station is further, by using one or more other weather stations in relay. The units are lightweight and easily installed. Data logging and radio transfer are accomplished via five “C” cell batteries charged by a 4-inch by 6-inch solar panel. The solar panel, antenna and rain gauge are atop a pole about 15 feet tall, while the leaf moisture sensor protrudes from the pole and into the vine canopy. Additional sensors for soil moisture, soil temperature, wind speed and direction, solar radiation and air pressure are available. Cost of a sending station can range from just over $3,000 for the basic unit to $6-7,000 for one with additional sensors. Software necessary to access the base station is another $990.

Primary among the uses of these weather stations by Napa growers is early disease forecasting. Growers have 24 hour a day access to measurements of rainfall, humidity, temperature, leaf wetness, wind speed and direction and air pressure. They can call up the data and relevant risk assessment models on their computer screens with information as current as the conditions of 15 minutes prior. Naturally, growers are most concerned with the conditions in their own vineyards, but they can have access to data from other weather stations in the network, too.

Powdery mildew is a source of ongoing anxiety for Napa growers, particularly early in the season. Heretofore, the prudent grower sprayed on a regular calendar basis on the presumption that too much and too soon were preferable to too little, too late. However, several potential advantages occur if spraying applications can be extended; i.e., done less frequently over the course of a season. Cost of chemicals is reduced, as is cost of labor in applying them. Less unnecessary chemical is introduced to the vineyard environment and, also, more days of access to the vineyards are gained.

Dana Zaccone, vineyard technician for Domaine Chandon in Napa’s Carneros region, says that the more precise information available to Chandon seems to be allowing for less frequent spray applications overall, allowing a cost saving. However, he notes that the model could predict a potential of mildew that might otherwise have gone unnoticed. In this case additional treatment cost would occur.

Growers have access to the data in an easily-interpreted form provided by the software package from Adcon and can schedule applications based on the software’s risk assessment model. The Gubler-Thomas powdery mildew model was developed by Doug Gubler, Ph.D., from the Department of Plant Pathology at U.C., Davis and Carla Thomas, vice president agriculture for Adcon Telemetry. Traditional viticultural practice has been to apply sulfur or fungicide for the conidia stage of powdery mildew which occurs most rapidly between 70 and 85 degrees. A key aspect of the Gubler-Thomas model predicts vulnerability to the ascospore stage of powdery mildew which becomes a risk in spring when three conditions occur simultaneously: vineyard temperatures exceed 50 degrees, shoots have grown at least two inches and leaves are moist for more than 12 hours per day. It is believed that treating early incidence of the ascospore stage will minimize problems of conidia outbreak late in the season.

Chris Davidson manages 120 acres of vineyard land for Kirkland Cattle and Vineyards in Napa County’s Jameson Canyon, adjacent to the Carneros. The first of her vineyards were planted in 1986 and the balance in 1995. Perhaps because of the relatively recent history of her plantings and their diversity (12 different varieties in all), Davidson is disinclined to take a “business as usual” approach. At present she has two Adcon weather stations; a basic unit in her original vineyards which she uses mainly for pest control and disease prediction and one with a wind meter for her new plantings which, being east of an irrigation field, have greater disease pressures because of the greater air moisture. Davidson’s concerns are primarily for mildew and bunch rot pressures and comments, “when I spray it usually cost several thousand dollars so you want some reassurance that you’re spending the money at the right time for the right reasons. I pay for my system the first time I eliminate one spraying.

“It’s a needed, emerging tool. I think there will be expanding uses and those who don’t accept this kind of technology will be guessing. A winery is more comfortable buying from a grower who has a better grasp of their disease problems – and is not just guessing.” Flexibility may be a key in utilizing this technology. Don Luvisi, University of California Extension Farm Advisor for Kern County, reports 13 sending units in his county, five south of Bakersfield and eight to the north. “I’m happy with the information and the equipment,” he says, “once I have confidence in the disease model and it says stretch my applications, I can do it. But I’m working with large growers probably none less than 1,000 acres and all equipment is scheduled.” To this point, adapting schedules for equipment and labor has proven a sticking point and Luvisi has not seen the program’s potential realized in his county.

While growers are most concerned with their own vineyards, information from any weather station is available to all participating in the network. Paul Kenney, who manages northern Napa Valley vineyards for Sterling, has weather stations on his properties in the Calistoga area but appreciates the access to everybody else’s information. Kenney says that the main reason for purchasing an Adcon system was for disease forecasting. While it did allow him to stretch his sulfur applications somewhat during the ’95 season with a consequent saving, the ’96 season has been so hot that powdery mildew has not been much of an issue. However, Kenney believes the long-term temperature tracking is an equally valuable aspect of the system. “Before, we had these old, wind-up thermographs which were hard to calibrate,” he says. “These systems are so much simpler. Especially because the hills here are all so different, long-term record collecting is important. You can see what temperatures were like over a five-to-ten-year period and can tell what varieties would do well in any vineyards you might acquire or develop that are similarly situated.”

Though the original programs were established in Napa, Sonoma and Kern counties, other networks are now expanding throughout California.

Overall, this technology has allowed most growers to produce healthier crops with fewer pesticides at a lower production cost. Observing this success in the grape industry, Western Farm Service is establishing a 450 weather station network in California which will service a variety of crops. Among these will be grapes, strawberries, citrus, tomatoes, potatoes, carrots, avocados, cotton, wheat and corn. Growers can purchase their own weather stations which are connected to these base stations and have computer access on a 24 hour basis or have the base stations fax information to them on a regular schedule. Western Farm projects they will have weather stations operating in 85% of California’s major agricultural areas by the end of 1996 and are establishing similar network in Oregon, Washington and Idaho.

Though powdery mildew may be of the greatest concern to Napa and Sonoma grape growers, various other diseases and insects pose peril to other crops. The AgroExpert software that comes with the weather stations addresses these. It can calculate degree-day values which are useful in crop growth, yield and harvest estimates, as well as insect management. Degree-day values also are important in determining when to release predatory or beneficial insects, allowing growers to use fewer insecticides. Wind speed sensors alert the grower when it is too windy to spray pesticides safely. Growers can use the same weather stations to schedule irrigations by calculating evapotranspiration values and by measuring soil moisture. With this tool, growers can reduce ground water contamination, conserve water usage and manipulate harvest dates and crop yields better. While participating farmers may not yet be able to change the weather, they are acquiring some tools to help them better decide how they will respond to it.

Further information about this technology can be obtained by calling Adcon Telemetry at (1) 800-352-5309.


Cellar Masters of America, a direct marketer and interstate shipper of premium wines, announced phase one of its national rollout by shipping wine to consumers in Kentucky, Illinois, Texas, Florida, New York State, Virginia, New Jersey and Delaware.

Consumers in these states order wine from out-of-state sources. Some 40 wineries, including Arbor Crest in Washington State, Blue Mountain Vineyards in Pennsylvania, Leelanau Wine Cellars in Michigan, Glenora Wine Cellars in New York State, Schramsberg Cellars in California and Mission Mountain Winery in Montana are participating in the program.

Cellar Masters has developed a network of wholesalers and retailers and the distribution channels for each state. Plus, the Traverse City, Mich. corporation will collect all state excise and sales taxes and will handle label approval and other state requirements for wineries not already selling in a particular state.

Eventually, consumers will be able to place orders by calling a toll-free number or by placing an order via Cellar Masters’ World Wide Web site.

For information, contact the firm at (616) 933-6163 or fax (616) 933-6169.


The recently-completed cork harvest in Portugal will yield about 165,000 tons of cork bark, nearly 55,000 tons more than last year. The Spanish cork harvest is expected to produce 110,000 tons.

Jochen Michalski, president of Cork Supply USA, said the harvest was slightly above average, but shortages caused by the small 1995 crop – down by 30 to 40% – has led to inventory shortages and a continuing rise in price for cork. Michalski expects prices to stabilize eventually.

“We now have a good supply of high quality cork. The present price inflation should moderate as demands are met and it becomes clear to the industry that the days of tight supply are over. Last year the price of cork was changing on almost a daily basis. I don’t think we’ll see that in 1997. The quality should also be more consistent. The bottom line is: don’t bank on the prices going down, but getting high-quality cork will be easier than it has been in the last two years,” Michalski said.

He also noted that the wet winter in Portugal and Spain has dramatically improved the condition of the cork forests. “I’ve never seen the trees as healthy and strong as they are this year.”

COPYRIGHT 1996 Hiaring Company

COPYRIGHT 2004 Gale Group

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