106N J. Environ. Monit. 1999 1 Second a laboratory study published in July demonstrated that monarch caterpillars either die or have stunted growth when they eat milkweed leaves dusted with pollen from Bt corn.4 Monarch butterflies are one of the best known and best loved butterflies in North America. Criticism of the technology sharpened as the media warned of �killer corn�. In the wake of the study biotechnology companies regulators and researchers have been rushing to determine its real world implications. A unique biopesticide Bt sprays are unique among pesticides. They are prized as an essential part of integrated pest management systems because they are highly eVective against many diYcult-to-control caterpillars. Bt toxins are as potent as the most potent chemical insecticide yet very short-lived so that the environmental eVects are negligible.These properties have led to a $60 million market for Bt biopesticides in the US.5 But widespread cultivation of Bt crops could lead to insect resistance to Bt sprays. To delay development of resistance to Bt entomologists have devised a defense based on traditional genetic theory and the mating habits of insect pests. Known as the high dose/refuge strategy it requires that Bt crops engineered to express high doses of the toxin be surrounded by non-Bt crops. The purpose of the high dose is to kill oV as many pests as possible. The purpose of the refuge is to produce susceptible pests. The goal is to ensure that any rare resistant insect that survives on the Bt crops mates with a susceptible pest from the refuge. According to William McGaughey professor emeritus of entomology at Kansas State University �It�s awfully important that we get these resistance management plans just right.If we are too cautious we may deprive ourselves of the benefits of this technology. If we are not cautious enough we may have to go back to using chemicals.� This strategy already an EPA requirement for some Bt crop registrations and soon to be a requirement for all raises numerous questions of insect ecology such as Will both sets of bugs be ready to mate at the same time? How far do they travel before they mate? Since evaluation of mating behavior in the field has not yet been addressed such questions have engendered vigorous debate about how big the non-Bt refuge must be. Since it is crucial that any development of resistance be quickly spotted and eliminated the strategy also raises numerous questions about monitoring fields of GM crops.These include What is the best and most eYcient way to determine whether resistance is developing? How far from the field is monitoring necessary? In 1998 EPA�s Scientific Advisory Panel6 evaluated the prevailing level of monitoring and made recommendations for the future. Baseline data concerning pest susceptibility are currently gathered and will prove essential to determine whether crop failures are caused by resistance or something else. But lacking are reliable laboratory methods to measure resistance levels. Since monitoring based on bioassays has limitations SAP recommended consideration of field-based approaches such as sentinel plots which are regularly monitored.Complex interactions The laboratory study conducted by John Losey and colleagues at Cornell University Ithaca New York pointed to a flaw in the existing regulatory framework according to Fred Gould an insect geneticist at the University of North Carolina Raleigh NC. Prior to the Cornell research almost every study suggested that Bt corn has minimal eVects on wildlife and beneficial insects. Three insect predators that eat European corn borers also eat corn pollen. But laboratory and field tests indicate that Bt pollen did not aVect them. Just one other study indicated a detrimental eVect on a beneficial species. Lab experiments by Angelika Hilbeck at the Swiss Federal Research Station for Agroecology and Agriculture in Zurich showed that green lacewing larvae that ate Bt-intoxicated corn borers suVered higher mortality.In the US cradle of genetically modified crops agricultural scientists and regulators are already tackling one environmental issue and rushing to determine the magnitude of another. The rise of genetically modified crops in the US represents a revolution of unprecedented speed. From a zero start just four years ago GM crops primarily soybeans cotton and corn accounted for 22 to 44% of the acreage planted in 1998.1 According to Charles Benbrook of Benbrook Consultant Services Idaho in the US all of the public and private institutions of agriculture the United States Department of Agriculture the Environmental Protection Agency the farm press and the private sector have for all intents and purposes embraced biotechnology as the wave of the future.Benbrook previously served as an agricultural policy analyst on the President�s Council on Environmental Quality.2 Although many scientists in research and agriculture have expressed concern over the speed of these changes direct opposition has come from environmental food safety groups and organic farmers. A coalition of these groups sued EPA in February 1999 in an eVort to force the agency to ban cultivation of transgenic corn cotton and potatoes that incorporate genes from a soil bacteria Bacillus thuringiensis (Bt). Then in July the Environmental Defense Fund petitioned EPA to restrict Bt corn. Now the Clinton administration is under pressure from environmental groups to require labeling of foods that contain biotech ingredients. Bt crops and in particular Bt corn have been the focus of opposition for two reasons.First and foremost from the onset Bt crops have presented an identified environmental threat�their widespread cultivation could lead to the development of insects that are resistant to Bt toxins.3 These toxins which are lethal to many caterpillars are currently used as environmentally benign pesticide sprays and form an important component of integrated pest management systems which seek to minimize the use of harmful pesticides. Focus Evaluating the environmental eVects of the GM revolution J. Environ. Monit. 1999 1 107N Focus Most previous studies looked for direct eVects and didn�t find them according to Losey. His work and Hilbeck�s instead looked at more complex interactions�that is where attention should be focused he said.Mindful of the monarch study and the growing controversy over GM crops the Department of Agriculture has asked an independent panel of scientists to review its process for approving new varieties. The National Research Council is funding a review of GM crop regulations which is due for publication early next year and EPA is conducting an internal re-evaluation. Many diVerent agencies are involved because in the US the overseeing of GM crops is split between the Department of Agriculture EPA and the Food and Drug Administration. But other scientists say that regulators are over reacting to a �very preliminary� report. They worry that a public backlash against genetically modified foods could slow development of crops that could improve health and nutrition. In October Anthony Shelton a colleague of the Cornell researchers spoke for many entomologists when he told members of Congress that �Scientists and policy makers should not be easily swayed by preliminary laboratory reports and the media.� However the reality is that shrinking foreign markets and emerging concerns at home are creating uncertainties for US farmers.7 Notes 1 Economic Research Service US Department of Agriculture �Genetically Engineered Crops for Pest Management� Impacts of Adopting Genetically Engineered Crops in the U.S.� Preliminary Results ( http://www.econ.ag.gov/whatsnew/issues/ biotech) 2 C.Benbrook. World Food System Challenges and Opportunities GMOs Biodiversity and Lessons from America�s Heartland. University of IllinoisWorld Food and Sustainable Agriculture Program meeting January 27 1999.( http://www.biotech-info.net/IWFS.pdf ) 3 J. Risler M. Mellon. The Ecological Risks of Engineered Crops; MIT Press Cambridge MA 1996. 4 J. E. Losey L. S. Rayor M. E. Carter. Nature 1999 399(6733) 214. 5 Return to thks Presented On Behalf of Consumers Union By Dr. Charles M. Benbrook and Dr.Michael Hansen Before the EPA Public Meeting��Plant Pesticides Resistance Management� March 21 1997 ( http://www.biotech-info.net/ stone-age-comments.html) 6 Final Report of the FIFRA Scientific Advisory Panel Subpanel on Bacillus thuringiensis Plant-Pesticide Resistance Management OPPTS-00231 United States Environmental Protection Agency U. S. Government Printing OYce Washington D.C. 1998. 7 S. Lehrman Nature 1999 401 107. Rebecca Renner Science writer and editor based in the US Tel:+1 570 321 8640 Fax +1 570 321 9028 e-mail applepie@sunli