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A Key Focus for Pest Management: Regulatory Issues for Water and Air Quality


Pesticides in water bodies have become an increasing concern of public and regulatory interest. Organophosphate insecticides have already been found widely in surface waters from both agricultural and urban use, and maintaining agricultural waivers for discharges has involved compliance activities from thousands of growers. There are also increasing concerns about pyrethroid insecticides and some herbicides in surface waters.

Under Section 303(d) of the federal Clean Water Act (CWA), the State is required to identify waters that do not meet water quality standards and develop a compilation, the 303(d) list of impaired waters. California's current Section 303(d) list can be found at http://www.waterboards.ca.gov/tmdl/. Examples of identified high priority sites impaired by currently used pesticides (as opposed to “legacy pesticides” such as DDT and toxaphene) include the Lower Feather River and the San Joaquin River.

There has already been a considerable amount of research in California to reduce the use of organophosphates (e.g., see http://californiaagriculture.ucop.edu/0501JFM/toc.html). There is a significant extension effort already under way to reduce pesticide loads reaching surface waters. However, more research may be needed on alternatives to organophosphates and other pesticides that impair waterways to assist growers in complying with current and pending regulations.


Agricultural Dust

Federal clean air laws require areas with unhealthy levels of ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and inhalable particulate matter to develop plans, known as State Implementation Plans (SIPs), that describe how the areas will attain national ambient air quality standards. Unfortunately, the Central Valley of California has particularly high levels of inhalable dust, especially particulate matter of less than 2.5 microns in size (PM2.5). A significant portion of inhalable dust is due to agricultural activities such as land preparation and harvest, but some is also due to tillage operations for pest management purposes, such as weeding and mandatory plowing of cotton residue for pink bollworm control, and passes across the field for spraying operations. Growers are currently encouraged to follow conservation management practices, including for pest management (see http://www.valleyair.org/farmpermits/applications/cmp/cmp_list.pdf).

More broadly, the adoption of reduced tillage practices will have implications for pest management, such as changes in weed species composition. Although the most important agricultural gains in reductions of PM2.5 will likely be from improvements in land preparation and harvest, a key consideration for pest management will be to ensure that weed, disease, or insect management is not an inhibition to broader adoption of practices that reduce dust generation and improve air quality.

Volatile Organic Compound (VOC) Emissions

Volatile organic compound (VOC) emissions and nitrogen oxides react with sunlight to create ozone, a major air pollutant. The Clean Air Act (CAA) requires states, through their SIPs, to reduce the emissions of VOCs and nitrogen oxides in areas that do not meet the ozone standard (non-attainment areas). Many pesticide active ingredients, as well as inert ingredients, are VOCs, and are of particular concern during the May to October ozone season.

Under the 1994 SIP, the California Department of Pesticide Regulation (DPR) committed to reduce VOC emissions from applications of pesticides by specified amounts within specified time periods for three current non-attainment areas. The pesticide VOC reduction goals (relative to 1990 base year) are

Southeast Desert 20% reduction by 2007
Ventura 20% reduction by 2005
San Joaquin Valley 12% reduction by 1999

Although there are still some uncertainties about the precise contributions of various pesticides and crops, the main contributors to pesticidal VOCs for these areas in terms of crops and chemicals are described at

Officially, emissions in the San Joaquin Valley currently exceed the 1999 target (which is the basis of a lawsuit filed last year against DPR), and there are additional targets over the next five years requiring reductions of at least another 20%. These targets will likely be subject to increased public and regulatory scrutiny, so alternative and cost-effective pest management tactics are of critical importance to the agricultural community.

The major contributors are fumigants, accounting for about 48% of the emissions, and pesticides with emulsifiable concentrate (EC) formulations, predominantly chlorpyrifos. For ECs, it is the formulations (rather than the active ingredients) that collectively account for about 37% of VOC emissions. The most important crops in generating emissions are carrots (estimated at 19% of the total VOCs, due to fumigation), cotton (13%, due to the use of pesticides with emulsifiable concentrates, mostly chlorpyrifos), almonds (8%, mostly fumigants for replanting orchards and chlorpyrifos EC use), grapes (6%, multiple sources including sulfur and fumigants), potatoes (6%, fumigants) and citrus (5%, mostly chlorpyrifos EC use). Recent changes in data for glyphosate suggest that it is a much smaller contributor than chlorpyrifos.

In practical terms, because of the relatively small contributions from so many other crops, the most likely way to meet the emission reduction goals in the San Joaquin Valley will be through reductions in the use or emissions of fumigants, especially in carrots but also potatoes and to a lesser extent almonds and grapes, and reductions in the use of EC formulations of chlorpyrifos in cotton, almonds, and citrus, without substituting other EC formulations. As noted above under water quality, there are also concerns about chlorpyrifos use in some areas due to water quality considerations.

In contrast to the San Joaquin Valley, fumigants alone are the major issue for the Southeast Deserts (especially carrots, estimated at 28% contribution, and peppers, 14%) and Ventura (strawberries, 85%). Significant reductions in fumigant use for all three crops are probably necessary to meet the VOC targets. A stakeholder meeting on September 23, 2004, found that a key limitation to the reducing the use of fumigants in carrots was improved sampling methods for plant pathogens.

To make the greatest gains for investment of resources, the larger sources of VOCs emissions should be targeted wherever there are potential IPM tactics that could be effective.

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