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Annual Reports

1999Water Quality and IPM

Identifying Agricultural Management Practices to Reduce Pesticide Runoff

The Situation

Organophosphate (OP) pesticides, especially diazinon and chlorpyrifos, have been routinely detected in water-quality monitoring projects coinciding with winter rains flooding dormant orchards in the Sacramento and San Joaquin River watersheds. These studies, conducted by both federal and state agencies, indicate that small invertebrates are killed when exposed for even short periods to the OP levels measured in the two watersheds during the winter. These invertebrates are indicators of the health of aquatic food chains and serve as primary food for many larval and juvenile fish.

Published and unpublished data reveal that one source of the OPs detected in tributaries and rivers is rain runoff from orchards. The magnitude and duration of the insecticide-caused toxicity following winter storms led the Central Valley Water Quality Control Board to declare this a violation of its Basin Plan water quality standard for toxicity.

In 1998, the State of California placed the Sacramento River and the San Joaquin River, as well as the associated Delta/Estuary, on the Clean Water Act 303(d) list of impaired waterways, partly because of elevated levels of diazinon and chlorpyrifos, presumed to originate at least in part, from dormant spray orchard runoff. These listings necessitate the development of Total Maximum Daily Loads (TMDLs). TMDLs will restrict the quantities of the OPs coming off of specific areas. Diazinon and chlorpyrifos are widely used in California for a variety of urban as well as other agricultural applications, and all uses are subject to restrictions stemming from the TMDL limitations. Additionally, OPs in general are primary targets of the Food Quality Protection Act of 1996 (FQPA).

Identifying agriculture's contribution to the problem is just one part of the issue. Its resolution requires understanding the specific agricultural production practices and the urban uses related to the problem, the mechanisms of off-site movement of pesticides, and then developing alternative practices to reduce pesticide runoff to a level that eliminates toxicity in surface waters.

The best solutions to these issues will be those that evolve from a solid information base coupled with input from the users of pesticides, including growers, landscape managers, urban and suburban residents, and the agencies charged with maintaining water quality.

The Role of the University

Acting on grants from the State Water Resources Control Board and the CALFED Bay-Delta Program, Statewide IPM Project Director Frank Zalom is coordinating a new programmatic effort with David Hinton, director of the Aquatic Toxicology Laboratory of the UC Davis School of Veterinary Medicine, and Barry Wilson, professor with the UC Davis Department of Animal Science and the Department of Environmental Toxicology. Michael Oliver of UC Cooperative Extension, Stanislaus County, serves as program manager. Steering committees, comprised of representatives from state agencies, grower groups, and local Cooperative Extension offices, provide direction for the projects.

One of their initial tasks was to provide detailed assessments of the current knowledge of alternative agricultural practices for reducing or eliminating pesticide use, particularly as it pertains to orchard crops and specifically as it pertains to the use of organophosphate (OP) dormant sprays. They issued a report in September of 1999 that outlined a number of viable alternatives to traditional OP dormant sprays for a variety of orchard crops. The report also contained an economic analysis of costs associated with the various alternatives. Although the alternatives can be somewhat more complex to administer and their costs can run higher than that of OP sprays, the report noted that the increased cost, relative to the total cost of production, was not large.

Building on the economic analysis of the report, Statewide IPM Project staff constructed a Web-based calculator for alternative practices that went online in January 2000. The Dormant Spray Alternatives Calculator can be used by growers and others interested in comparing costs associated with various alternatives. Users can choose to accept default cost values for production parameters (for example, pesticide used, rate of application, method of application, and monitoring costs), or they can enter their own values instead. Note: This calculator is no longer available due to significant changes in stone fruit and almond pest management practices since 1999.

In addition to the assessments, the project members developed a number of educational documents and conducted workshops to provide information to growers and pest control industry personnel. Information focused largely on explaining what the problem is, agriculture's role in the problem, and the alternatives available to help eliminate the problem. A number of grower and industry organizations added significantly to the outreach efforts by publishing and distributing newsletters and pamphlets emphasizing the messages coming from the UC efforts.

Current and Future Goals

The UC program is currently focusing its resources on four main areas:

  • Continuing and strengthening the educational efforts to assist agriculture
  • Developing an effective educational effort aimed at the most appropriate urban audiences
  • Conducting field studies to investigate a variety of potential management methodologies for reducing dormant spray runoff from orchards, and
  • Developing methods to better assess the chemical composition and hydrology of orchard runoff.

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