By Parry Klassen
(This article was published in the August 2002 edition of California Farmer and is reprinted with permission)
"Optimism" isn't a term most would associate with organophosphate (OP) insecticides these days.
Still, despite tightening regulatory standards, this widely used class of insecticides - including Lorsban, Guthion, Imidan and diazinon, among others - is likely to remain available for critical uses. Once the regulatory dust has settled, those uses that growers defend as essential are the ones likely to be around for the long term.
OP registrants give much of the credit for preserving important crop uses to commodity groups and minor crop growers. These "stakeholders" have provided U.S. Environmental Protection Agency with critical data about how products are actually used in the field so risk assessments more accurately reflect those uses. Equally important is the groups' convincing EPA that effective replacement products are lacking or even when they do exist, OPs play an important role in managing resistance so the alternatives remain effective.
"We have frequent, sometimes weekly, communication with EPA as different compounds come up for re-registration," says Chris Heintz, research director for Almond Board of California. "The on-going interchange provides EPA with real-world information they need to evaluate products, especially as it relates to the importance of OPs to our Integrated Pest Management programs."
In addition to the Almond Board, the California Dried Plum Board and California Grape and Tree Fruit League and others have been writing letters, participating on U.S. EPA conference calls and undertaking concerted efforts to be heard when OP label decisions are made in Washington, D.C.
Continued use of Lorsban (chlorpyrifos) on many fruit and vegetable crops can be attributed in large part to growers providing direct input to EPA. In November 2001, Lorsban passed a major reregistration review required for all older pesticides introduced prior to 1985. As with other OPs, Lorsban had to undergo an evolving health and safety review process that lasted nearly 10 years. This was due in part because regulators requested new or upgraded scientific data to address potential or hypothetical concerns.
The decision by EPA to grant Lorsban a favorable interim reregistration eligibility decision (IRED) was a relief to growers and Dow AgroSciences, the primary product registrant.
"This decision proves that constructive input with accurate data from commodity groups can result in product uses being preserved," says Dr. Bryan Stuart, western regional government relations manager for Dow AgroSciences.
Lorsban didn't make it through the review process unscathed. With a program Dow AgroSciences calls its "label improvement initiative," plans are in the works for label changes that add wider buffer zones to fields near water, longer re-treatment intervals and new personal protective equipment requirements. These label changes, Stuart explains, "provide added environmental protection and more safeguards for growers, workers and applicators who handle the product. They are also important in light of surface water quality issues in California on runoff from ag lands."
Another widely used OP, Guthion (azinphos methyl), went through a more bruising IRED review by EPA yet keeps key crops and uses on its label, at least for now. In an agreement between EPA and registrants called a "time limited registration," uses on almonds, apples, walnuts, pears and other minor crops will expire on October 31, 2005. EPA is giving Guthion registrants Bayer and Makhteshim-Agan those four years to continue the approved uses, albeit with restrictions, while they develop new data on occupational exposure.
"By working with commodity groups, we have been able to provide EPA with real-world information on Guthion use, which is extremely important when determining whether a product poses a health risk," says Dr. Gregg Storey, manager of product stewardship for Bayer Corporation. "Initial dietary risk calculations in 1999 by EPA showed that Guthion filled the theoretical 'risk cup' by 10,000%. More refined assessments reduced that number to a more realistic 10% of the risk cup," says Storey.
A restriction becoming more common for OPs is enclosed cabs for tractors towing orchard air blast sprayers. Lorsban will have such language on its label in 2004 or require operators without cabs to wear gloves, respirator, face shield and a double layer of clothing. Guthion already has the requirement on its label.
Similar restrictions are being proposed for orchard uses of Imidan (phosmet), an OP insecticide made by Gowan Co. A final IRED expected to be released in summer 2002 should allow continued use on all crops currently listed on the label, says Cindy Baker, president of Gowan. "While urban uses for phosmet will be discontinued, existing crop applications can continue, although the final IRED will likely include new requirements for enclosed cabs or additional personal protective equipment," she says.
Still uncertain is the fate of diazinon, one of the most widely used OP insecticides. A final IRED is expected by summer, explains Ephi Gur, manager of regulatory and scientific affairs for Makhteshim-Agan North America, primary registrant of the product. "We are working with grower groups now to determine which crops need to remain on the label. All urban and indoor uses are being phased out by December 2002 but we are hopeful many crop applications, for now, will remain available," says Gur.
Ironically, total use of OP insecticides is declining in California due in part to new product introductions and the tough economic times facing agriculture. Still, grower groups are determined to preserve OP uses because of their importance to Insect Resistance Management and Integrated Pest Management programs.
Concerns about worker exposure to OPs are being addressed through label changes and widespread adoption by growers of strict worker protection standards that apply to the products. Proof of these improvements are the most recent pesticide exposure statistics from the California Department of Pesticide Regulation that show a decrease in worker exposure incidents involving OPs.
Regulatory pressure can only be expected to increase with time on older classes of insecticides such as the organphosphates. Still, experience with the current round of IREDs proves grower input makes a big difference in which products do remain available for fighting pests.
(Parry Klassen, based in Clovis, is a freelance writer and Executive Director of the Coalition of Urban, Rural Environmental Stewardship (CURES.)