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Status Report for the PPDC: Resistance Management For Bt-crop
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Note: This information is provided for reference purposes only.
Although the information provided here was accurate and current
when first created, it is now outdated. |
There are currently 8 registered Bacillus thuringiensis (Bt)
plant-pesticides. There is one registration each for Bt potatoes, Bt cotton,
and Bt popcorn; and there are 5 registrations for Bt field corn. One of these
Bt field corn products (Novartis' Event 11) is also registered for
processed sweet corn.
Resistance management for Bt-crops was one of the first issues brought to
the Pesticide Program Dialog Committee (PPDC). At the time of that meeting,
resistance management for Bt crops already was an issue being discussed by
EPA, registrants, and public interest groups at Scientific Advisory Panel
(SAP) meetings. In addition, registrants were conducting research on the
biology and ecology of affected insects and crops to better understand long-term
resistance management of Bt-crops to slow or halt the development of insect
resistance. Of special consideration were the microbial forms of Bt used
in Integrated Pest Management (IPM) programs because of their importance
to sustainable agriculture and organic farming. That first PPDC cautioned
EPA not to require resistance management plans for all pesticides, while
acknowledging that Bt was a special case ("in the public good") and worthy
of extra protection.
Subsequent to registration of the first Bt crops in 1995, a great deal has
been learned which has been helpful in better understanding the need for
and refining resistance management plans. A USDA organization known as NC
(North Central) 205 issued a report in 1997 for Bt corn which recommended
refuges or set-asides using non-Bt corn acreage as a major component of
resistance management plans. EPA has also received a detailed, final report
from the February 9, 1998 SAP Subpanel meeting on Bt resistance management;
and the International Life Sciences Institute (ILSI) is in the process of
finalizing their report which focuses on Bt resistance management for corn.
In January of this year, in preparation for another SAP meeting on Bt crops
and resistance management, EPA released a report summarizing our current
understanding of this topic. Shortly afterwards, the Union of Concerned
Scientists published their report entitled: Now or Never, Serious New
Plans to Save a Natural Pest Control. Additional knowledge on Bt resistance
has been garnered from annual research reports on Bt resistance submitted
to EPA by registrants of Bt plant-pesticides; Agency hearings and participation
in regional and national workshops; and extensive literature review on Bt
resistance conducted by EPA scientists.
A significantly larger rate of adoption of Bt plant-pesticides technology
has occurred than what was expected by registrants and by EPA at the time
the initial Bt products were registered. This is especially true for Bt-corn.
Although the 1998 data is not yet available, preliminary estimates have Bt-based
plant-pesticides representing 15 to 17 percent of the field corn crop in
the US, and adoption of Bt-based plant-pesticides rising to a high of 25
percent in 1999. Surprisingly, in 1995 it was estimated that the adoption
of Bt-based plant-pesticides would be about five percent by the year 2001.
Mindful of the accelerated adoption rate, EPA and USDA have agreed to re-examine
Bt crop resistance and resistance management strategies. EPA and USDA intend
to use a public dialog process to include researchers, registrants, growers,
public interest groups, and government agencies to identify reasonable approaches
to resistance management. The PPDC meeting is not intended to discuss the
exact size and location of refuges or set-asides that government agencies
and growers would support, but rather to present and discuss the general
framework and process for enhancing the knowledge base on Bt resistance and
management of plant-pesticides. In addition, EPA and USDA are jointly authoring
a working paper to serve as the central discussion piece for a planned workshop
in early March aimed at exploring ways of designing and implementing resistance
management programs that are flexible and can accommodate rapidly changing
technology (e.g., gene stacking or adding additional Bt proteins, and adding
new non-Bt genes to crop plants).
EPA is also actively considering changes to existing registrations, especially
for Bt potatoes and certain Bt corn registrations, to stipulate similar refuges
or set-asides as those listed in the registrations for Bt cotton. The size,
location, and time frame for implementing these set-asides would be a major
focus of the proposed March workshop. EPA and USDA would like to have consistent
refuge or set-aside requirements for similar Bt crop registrations where
appropriate; however, some Bt-proteins may turn out to be so unique that
refugia or set-aside acreage could be reduced or even eliminated for those
products. In addition, regional differences in climate, pest/crop combinations,
and pest biology may call for different resistance management plans, e.g.,
the pink bollworm control program in Arizona.
In the long-term, a regional approach to resistance management for
plant-pesticides is gaining support. USDA is considering the development
of "virtual centers" around the country to be staffed by commodity experts
from the USDA and grant partners. While the centers would serve a number
of functions, one role discussed has been development of regional resistance
management plans for Bt-based crops. These regional centers could help establish
appropriate regional resistance management strategies for the Bt crops grown
in that area.
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