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Resistance Management Reviews
US EPA's Role in Resistance Management
Richard T. Roush
Department of Entomology
Cornell University
Ithaca, NY 14853
United States
Address starting July 1:
Department of Crop Protection
Waite Institute
University of Adelaide
Glen Osmond, South Australia
Australia
At least since the early 1980's, various individuals and groups have urged the US Environmental Protection Agency (EPA) to take a more active role in resistance management. As outlined by Mike Dover and Brian Croft ("Getting Tough: Public Policy and the Management of Pesticide Resistance, published in 1984 by World Resources Institute), the EPA has a profound (and not altogether beneficial) impact on resistance management by virtue of its current regulations and could significantly improve resistance management with the adoption of additional or alternative policies. The merits of these proposals have been debated at length at various meetings, including by a committee of the National Academy of Sciences ("Pesticide Resistance: Strategies and Tactics for Management", 1986) and at various meetings of professional societies, including the Entomological Society of America. Recently, various public interest groups have added their voices to the chorus, urging that the EPA refuse to approve Bt-transgenic insecticidal crops until the "EPA has in place workable, enforceable resistance management strategies".
There is insufficient space here to review these debates, but it seems clear that the EPA is reluctant to use regulation to help delay resistance to pesticides. In the EPA's defense, it may not have to do so. EPA has made some modest Proactive efforts in avoiding resistance, such as requesting resistance management statements from some companies developing transgenic plants and more traditional pesticides. Nonetheless, in the absence of any efforts to enforce or facilitate the adoption of resistance management plans, such documents clearly have little more than public relations or educational value.
My main point in this editorial is to suggest how we might encourage the EPA to be a more effective partner in managing resistance without requiring any expansion of EPA's legal mandates or any significant increase in the work load of its already overburdened staff. I base my suggestions on recent experiences with both transgenic crops and imidacloprid, a novel insecticide with major applications in control of whiteflies and the Colorado potato beetle, pests which are notorious for resistance evolution.
Knowledge is power, or at least influence. In the case of imidacloprid, the insecticide can be used for Colorado potato beetle (CPB) control either as a soil application or a foliar spray. The soil application (tradename "Admire") has a half-life of some 50 days (controlling the entire first generation of CPB), whereas foliar sprays (tradename "Provado") have a half-life of 1-2 days. Due to the greater persistence of the soil applications, 1-3 applications of Provado would be preferable to a soil application of Admire in a resistance management program. Several potato entomologists urged both EPA and the US registrant (Miles Inc.) to support labeling of both Admire and Provado to assure local flexibility in resistance management efforts. Unfortunately, many of us were unaware of a lack of residue data that forced EPA to require a 12 month "plant back" restriction for both Admire and Provado. Currently, this essentially means that the land on which an imidacloprid application has been made to potatoes cannot be rotated to another crop for at least 12 months. Crop rotation is very important in potato production, with important agronomic advantages (including disease suppression) in addition to being a most effective tactic for managing resistance in CPB (the adults must hunt to find a new potato field, which slows population growth and reduces dependence on insecticides). Since Admire is applied at planting (often at least 12 months before a rotational crop would be planted), this is not a limitation to the soil applications, but is a severe impediment to the use of Provado, which would be applied later in the season. In sum, the lack of adequate residue data has severely impeded efforts to prevent or delay resistance to a valuable new insecticide. A further complication is that growers have now made the investment in new equipment to apply Admire, which will inhibit their willingness to switch back Provado when and if the residue questions are resolved.
While entomologists were unaware of residue data gaps and their implications, the appropriate EPA officials were in turn apparently unaware of the importance of crop rotation in potato production and pest management. Thus, while the data gaps might have been raised by the EPA and addressed in a timely fashion by the registrants, we are now faced with a considerable obstacle to resistance management, the plant-back period. It would be naive to think that companies will always be willing to generate the data necessary to avoid problems such as this. However, it must certainly be true that improved communication between resistance managers and the EPA could help to avoid such problems among parties of good intentions.
I encourage readers to write to the EPA at the earliest opportunity with any serious concerns about resistance management for new products. Each individual, in consultation with colleagues, will have to decide whether his or her concerns are truly serious, remembering that EPA staff are already overburdened, and that too much letter writing will only diminish attention to the most serious problems. To make sure that letters get distributed to all relevant parties in the agency, send letters to management. Currently, the appropriate officials are two Division Directors of the office of Pesticide Programs: Mr. Stephen Johnson (Registration Division, 7505C) and Dr. Janet Anderson (Biopesticides and Pollution Prevention, 7501W), both at EPA, 401 M Street, SW, Washington, DC 20460. If you know the specific product manager at EPA, send him or her a copy.
In general, more companies should submit resistance management statements to the EPA about their new products. Even as I type this, I can hear the collective groan from pesticide companies around the world, who have often voiced their opinion that this is not something in which the EPA should get involved. However, before rushing to judgment, I think companies would do well to study the approach that has been taken by Monsanto in considering resistance management for its Bt-transgenic crops. During a Scientific Advisory Panel (SAP) meeting at EPA on March 1, 1995, Monsanto was praised by both contributors from the public and SAP members for the thoroughness of its resistance management proposals. To develop these proposals, Monsanto has not spent vast sums on research, but relied extensively on meetings with researchers in the pubic sector and some modest support of their research. I am confident that if asked, the participating Monsanto personnel would agree that they have learned a lot of useful information in the process. I believe that I can speak for other University and USDA scientists in noting that we learned a lot from Monsanto. My point here is not mutual "back-patting", but that this process can clearly be much less onerous than industry has feared. In many if not most cases, resistance management plans for other systems can be developed at far less expense. The strategies in resistance management are often fairly obvious; the problem is more often in implementation, which could be facilitated by better communication between government and industry.
In the long term, the EPA should work toward offering encouragement and inducements to companies to help them manage resistance, and to reward those who do (such as faster processing of registrations which include label restrictions to promote resistance management). In the meantime, however, improved efforts at making the EPA aware of resistance management issues empowers them to help us in the field. In extensive discussions and correspondence over the last few months, I have found the EPA to be willing to help; it remains up to us to try to educate the EPA about what is needed. The EPA will not be able to solve all of our implementation problems in resistance management, but I am convinced that the EPA can be helpful in at least some instances.
Supported By:
Editors:
Mark
E. Whalon
Robert M. Hollingworth
Area Editors:
Plant Pathology
Margaret Tuttle McGrath
Herbicide
Jonathan Gressel
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