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Annual Reports

1997California PestCast: A Weather Network to Support Crop Disease Management Decisions

California PestCast is a program funded by US EPA to advance development and validation of crop disease models for use in decision making. UC IPM agricultural meteorologist Joyce Strand coordinates the program under contract from the California Department of Pesticide Regulation. The original proposal was developed by Department of Pesticide Regulation, UC IPM, and Campbell Soup Company.

The overall goal of the new project is to expand the use of computer-based crop disease forecasting to improve the timing of fungicide applications. The project is developing a public-private weather network in support of research and validation of disease models and will promote crop disease model research, validation, and outreach to encourage adoption of this technology.

Although disease models are specifically targeted, the weather network will also be used to support work on insects, weeds, and nematodes. Weather monitoring equipment for eight projects was supported in response to a call for proposals issued in spring 1996.

The project has been directed by a steering committee: Jenny Broome and Paul Gosselin (DPR), Bob Curtis (Campbell Soup Company), Kim Crum (CAPCA), and coordinator Strand. This group provides direction and determines which model projects will be funded. A technical advisory group of researchers is also in place.

The Weather Network

PestCast is not funding research directly, but instead supports projects by purchasing and installing weather stations that supply environmental data needed by the research. So far, 23 stations have been installed in seven areas, monitoring air temperature, relative humidity, rainfall, leaf wetness, and in some cases solar radiation or wind. The stations are all equipped with radio or telephone telemetry so that data are acquired remotely to facilitate model output updates.

The data, reported in hourly or 15-minute increments, are gathered into the UC IPM computer system, quality controlled, then good data are stored. Researchers can then view or download the data over the World Wide Web to use in model calculations.

Weather stations were purchased under a competitive process, and Weather Network, Inc. of Chico was awarded the contract to provide Campbell Scientific equipment. In some areas, where for efficiency stations needed to be integrated into an existing network, compatible equipment was required. In several of these cases, weather stations from Adcon Telemetry were purchased.


Funded Projects

Cliff Ohmart
Cliff Ohmart, leader of the PestCast grape project in San Joaquin County, next to a weather station in a project vineyard. Photo by Joyce Strand.

Augmenting Weathernet, an automated weather information network for San Joaquin County, and implementing areawide use.

Project Leaders and Cooperators: C. Ohmart, Lodi-Woodbridge Winegrape Commission; J. Grant, UC Cooperative Extension, San Joaquin County; P. Verdegaal, UC Cooperative Extension, San Joaquin County; K. Kautz, Kautz Family Farms

Description: Crop-pest system: Grapes/powdery mildew, grape leafhopper, and omnivorous leafroller.

The project will collect data to validate the powdery mildew model, demonstrate the utility of that model to growers and PCAs, and promote implementation of grape leafhopper and omnivorous leafroller degree-day models. The three PestCast stations will augment the Weather net network in San Joaquin County, bringing the number of stations to 15.

PestCast Contribution: Three weather stations in San Joaquin and southern Sacramento counties, telephone service.


Implementation of downy mildew weather forecasting system on iceberg lettuce.

Project Leaders and Cooperators: E. A. Kurtz, Iceberg Lettuce Advisory Board, Salinas; V. E. Rubatzky, Vegetable Crops, UC Davis; C. S. Thomas, Adcon Telemetry, Santa Rosa; S. Koike, UC Cooperative Extension, Monterey County; F. Laemmlen, UC Cooperative Extension, Santa Barbara County, Santa Maria; A. Fox and J. Boyd, Fox Weather, Oxnard

Description: Crop-pest system: Iceberg lettuce/downy mildew.

The purpose of the project is to refine the leaf wetness and disease risk assessment parameters and the impact on grower production practices, associated with use of a downy mildew model on iceberg lettuce. As the model is validated and refined, implementation efforts will be undertaken. The work is being carried out in the Salinas and Santa Maria areas, and funded by several agencies, and growers, with most weather stations contributed by chemical companies. The entire network consists of thirteen stations in the two research areas.

PestCast Contribution: Two weather stations, maintenance of 13 stations.


Processing tomato disease forecasting: A private & public initiative in processing tomatoes.

Project Leaders and Cooperators: C. Rivara, California Tomato Research Institute, Inc., Escalon; R. M. Davis, Plant Pathology, UC Davis; J. Welty, Processed Tomato Foundation and California Tomato Growers Assoc.; G. Miyao, UC Cooperative Extension, Yolo County; B. Mullen, UC Cooperative Extension, San Joaquin County; H. Bolkan, D. Larsen, R. Curtis, Campbell Soup Company.

Description: Crop-pest system: Processing tomatoes/black mold, powdery mildew, and late blight.

The goal of the project is to validate and refine the TomCAST model (as adapted by Campbell Soup Company) for timing fungicide applications to control black mold; to validate and implement a UC Cooperative Extension powdery mildew model that forecasts outbreaks based on temperature, relative humidity, and duration of leaf wetness; and to adapt the TomCAST model for timing fungicide applications to control late blight.

Initiated and managed by the processing tomato industry and made possible by funds from several groups, a regional weather reporting network has been developed for the southern Sacramento Valley. This network of remote controlled weather stations is available during the growing season and is being used for model validation and to assist PCAs in forecasting black mold treatments with improved accuracy.

The network consists of 11 stations in Yolo, Sacramento, San Joaquin, and Sutter counties.

PestCast Contribution: Two weather stations, one base station, cellular phone service for eight stations.


On-site weather monitoring system for modeling of pear pests and diseases.

Project Leaders and Cooperators: G. T. McGourty, UC Cooperative Extension, Mendocino County; D. Gubler, Plant Pathology, UC Davis; S. Lindow, Plant Pathology, UC Berkeley; L. Varela, UC IPM and UC Cooperative Extension, Sonoma County; D. Gordon, Ag-Unlimited, Inc., Ukiah; P. Chevalier, United Ag Products, Ukiah; C. Thomas, Adcon Telemetry, Santa Rosa

Description: Crop-pest systems: Pears/scab, codling moth, obliquebanded leafroller, fire blight.

The primary focus of the project is to refine and incorporate a pear scab ascospore maturation model into a disease risk index, using on-site weather stations. Use of the model is expected to increase the effectiveness of the presently used Mills Tables index to predict infection periods, by quantifying the availability of primary inoculum during the growing season. The work will use the Mills Tables, along with spore trapping and prediction using a new model developed by Spotts and Cervantes in Oregon for ascospore maturation.

Additionally, codling moth and obliquebanded leafroller degree-day models will be validated, and the Cougar Blight fire blight model (developed by Tim Smith at Washington State University) will be evaluated for applicability to California.

PestCast Contribution: Three weather stations, two repeaters, analysis computer.


Development of Alternaria leaf blight of carrot disease forecasting model.

Project Leaders and Cooperators: J. Nunez, UC Cooperative Extension, Kern County; M. Davis, Plant Pathology, UC Davis

Description: Crop-pest system: Carrot/Alternaria leaf blight.

The project's goal is to validate and refine as necessary a model based on observed weather to forecast leaf blight occurrence and the optimum time to apply fungicides for disease control. Work is being done in Kern County, and the model being validated was developed specifically for carrots grown in the San Joaquin Valley.

PestCast Contribution: One weather station


Weather station network for validation and implementation of tomato disease forecast models.

Project Leaders and Cooperators: K. Brittan, UC Cooperative Extension, Sacramento County; M. Cahn, UC Cooperative Extension, Sutter/Yuba Counties

Description: Crop/pest system: Processing tomatoes/black mold, powdery mildew, and late blight.

The goal of the project is to validate and refine the TomCAST model (as adapted by Campbell Soup Company) for timing fungicide applications to control black mold; validate and implement a UC Cooperative Extension powdery mildew model that forecasts outbreaks based on temperature, relative humidity, and duration of leaf wetness; and to adapt the TomCAST model for timing fungicide applications to control late blight.

PestCast Contribution: Three weather stations with cellular phone service.


Updating the Lake County weather network to accommodate pest management research.

Project Leaders and Cooperators: R. Elkins, UC Cooperative Extension, Lake County; M. Lockhart, Lake County Department of Agriculture; R. Reynolds, Lake County Air Quality Management District

Description: Crop-pest systems: European pears/pear scab, fire blight, codling moth, obliquebanded leafroller; wine grapes/powdery mildew; English walnuts/codling moth, walnut blight.

The project aims to validate disease and insect models on pears, wine grapes, and walnuts in Lake County, then take steps to foster implementation by growers and PCAs. The Lake County Air Quality Management District and Lake County Fruit Frost Trust Fund will also contribute.

The new stations will be a part of a network of approximately eight stations.

PestCast Contribution: Three radio telemetry weather stations, one base station, telephone lines.


Central San Joaquin Valley grape production region.

Project Leaders and Cooperators: J. Kretsch, Sun-Maid Growers of California; M. Costello, UC Cooperative Extension, Fresno County; G. Leavitt, UC Cooperative Extension, Madera County; R. Coviello, UC Cooperative Extension, Fresno County; B. Peacock, UC Cooperative Extension, Tulare County; B. Beede, UC Cooperative Extension, Kings County; M. Mayse, CSU Fresno; D. Weinman, California Table Grape Commission

Description: Crop-pest system: Raisin, table, and wine grapes/powdery mildew, omnivorous leafroller.

This project will work on validation of the UC Davis grape powdery mildew model in raisin and table grapes in the central San Joaquin Valley. This work will document differences or similarities in model performance between raisin and table grapes. Verification of a model for omnivorous leafroller will also be conducted.

The new stations will form a new research network of six stations.

PestCast Contribution: Six radio telemetry weather stations, one base station, telephone lines.

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