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Research and IPM

California PestCast: Description

Compiling disease model data DPR logo

California PestCast, a project of the University of California Statewide IPM Program and the Department of Pesticide Regulation, is geared toward expanding the use of computer-based crop disease forecasting and reducing unnecessary pesticide use in California.

Weather networks
Models and validation projects


The overall goal of the PestCast project is to expand the use of computer-based crop disease forecasting with the goal of reducing unnecessary pesticide use.

The program

  • developed and implemented weather networks in support of adaptive research and validation of disease models
  • sponsored adaptive research and validation of disease models to improve crop disease management
  • conducted outreach to promote adoption of the new pest management technology by growers and consultants


Management of diseases in many California fruit and vegetable crops relies heavily on the use of fungicides as the most effective means of protecting the crop from quality and yield losses. In many crops, fields are sprayed on a regular schedule, often as much as weekly throughout the growing season. An effective means of reducing fungicide use is to improve spray timing by basing it on evaluation of risk of infection rather than on a calendar spray schedule.

In recent years, scientists have made progress in developing models that describe the relationships between environmental variables and disease development. To ensure widespread applicability, the descriptive models must be validated across the variety of microclimates where they will be applied. However, such validation requires a large-scale effort in weather monitoring, field data collection, and analysis.

Taking advantage of new environmental monitoring technology and interest in pest management model applications, a project funded by California Department of Pesticide Regulation through a grant from U.S. EPA, University of California, and the California agricultural industry, is providing an infrastructure to collect appropriate weather data, facilitate the research and validation of models of diseases (and some insects), demonstrate their utility, and further local implementation efforts.

Based on proposals from industry and scientist participants, regional weather networks were set up to monitor air temperature, relative humidity, leaf wetness, precipitation, and other variables as needed. Data is gathered centrally from most of the stations. quality-controlled, stored, and made available to users. This environmental information, along with field scouting reports, is being used in model development, validation, and correction.

As disease and insect models are validated, the data is transferred to growers and pest management consultants responsible for making treatment decisions. Throughout the growing season, disease indices are computed centrally, using validated models, then disseminated by computer.

Weather networks

UC IPM has continued to support the collection of data from several weather networks, even after funding for the initial PestCast grant ended. To retrieve the data, select the specific network in the California Weather Database. Data is reported for daily, hourly, and in some cases, sub-hourly intervals, for a variety of variables. See each station's description for information on a specific station.

UC IPM retrieves data from the networks once or twice daily. In most cases a computer in the local UC Cooperative Extension (UCCE) office is set up to call each station in a particular network, then the data files are transferred over the Internet to UC IPM. UC IPM quality-controls and stores the data, and reports problems to the local weather network administrator, if needed.

California Tomato Weather Network. Each year since 1998, UC researchers and the California Tomato Research Institute have installed weather stations in processing tomato fields across the southern Sacramento Valley and the northern San Joaquin Valley. These stations provide weather data and disease indices for use by growers and researchers in the control of

  • Blackmold
  • Powdery mildew
  • Late blight

Lake County Pear and Grape Network. The Lake County network is a cooperative effort among UC Cooperative Extension, the Lake County Air Quality Management District (LCAQMD), and the Lake County Department of Agriculture. The Lake County network is unique among PestCast systems in its multifunction purpose: pest management research, air dispersion, fire hazard, and agricultural/fruit frost data collection.

PestCast contributed the base computer, located in the UCCE office, and three weather stations. The LCAQMD purchased additional stations. WeatherNews, Inc. of Chico, the statewide PestCast contractor, handles system installation, calibration, and maintenance. The UCCE Pomology program, LCAQMD, the Lake County Fruit Frost District, and the Lake County Winegrape Commission share the network's annual maintenance expenses.

Fresno-Madera Grape Network. The Fresno-Madera network is comprised of eight stations originally supplied by PestCast, and is located in wine, table, and raisin vineyards in the two counties. Until 2002, UC IPM supported maintenance and phone lines for the network; today local industry and individual growers assume the responsibility.

The network supports work on grape powdery mildew, Botrytis cinerea, and several insect pests.

Coastal Strawberry Network. The strawberry network is a set of weather stations being used to validate a model of gray mold, Botrytis cinerea, on strawberries. A US EPA grant supported the research through 2003.

San Joaquin WEATHERNET. Stations in this network are scattered throughout San Joaquin County orchard and vineyard sites, including almonds, walnuts, grapes, and cherries. Growers own their own stations and contribute data to the network. UCCE oversees the network, but growers-owners maintain their stations and supply phone access.

Models and validation projects

The disease, insect, beneficials, and plant models databases describe the basic variables and calculations required by the models. They also cite the source of the model.

Data in the California Weather Database may be used to run any of the insect, beneficials, and plant models, using the degree-day calculator.

For more information about using the disease models, see the Pest Management Guidelines, the database entry, or the stand-alone model.

Powdery mildew of grapes (use your own weather data or data from PestCast grape stations).

Blackmold of processing tomatoes (use your own weather data or data from California Tomato Network).

Tomato powdery mildew (use your own weather data or data from California Tomato Network).

Tomato late blight (use your own weather data or data from California Tomato Network) .

Botrytis cinerea in strawberries or grapes.

Scab in apples or pears (use your own weather data or data from California Weather Database).

Fire blight in apples or pears (use your own weather data or data from California Weather Database).

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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Agriculture and Natural Resources, University of California

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