By Charles H. Featherstone
WASHINGTON (B)--U.S. farmers who grow crops genetically altered to produce their own insecticide must manage those crops carefully or risk the premature emergence of insects able to overcome the defenses of those biotech crops, experts told the EPA independent Science Advisory Panel Oct. 18.
"We need to protect this technology for as long as possible," University of Georgia researcher Gary Herzog told the panel.
The independent advisory panel, made up of agricultural researchers from across the United States, is reviewing EPA rules governing the planting of Bt corn, cotton and potatoes across the United States.
Bt crops use genes from strains of the bacillus thuringiensis (Bt) to produce a natural insecticide lethal to the larvae of pests like the European corn borer and the cotton bollworm.
Biotech industry officials and representatives of cotton and corn groups told the panel that there was little evidence to show that insects are building up resistance to Bt crops.
The possibility that insects may eventually become resistant to Bt--based on a scientific analysis of how bugs breed--means that farmers need to set aside some farmland in order to prevent the kind of inbreeding that would produce a super bug.
It is what EPA calls "refuge requirements," or the amount of non-Bt cropland that must be sowed in or near Bt crops in order to ensure that insects will not develop resistance too quickly to the Bt insecticide by breeding solely with other insects that survive Bt.
The panel heard that refuge requirements will vary from state to state, depending upon how much Bt cropland exists in a county, the local climate and even the lay of an individual farmer's land.
Typical of options given in a locality will be for a farmer who plants Bt cotton, for example, to sow 80% of his land in Bt and the remaining 20% in non-Bt cotton. That refuge could be located in strips within the Bt cotton, or in a block in or near the Bt field, depending on how fast and far insect pests such as the cotton bollworm can move during its short life cycle.
One plan to allow 95% planting of Bt cotton and 5% non-Bt in the cotton belt came under criticism from environmental groups because it risked creating resistant bugs much sooner than the models predict and would make it impossible for farmers to use the Bt chemical insecticide.
"The 5% refuge plan is quite laughable," said Greenpeace researcher Doreen Stabinsky. "The loss (of the use) of Bt (insecticide) is not a credible end point."
However, biotech industry officials said that if rules on refuge requirements are too strict, farmers will simply ignore them, thus more rapidly contributing to the pests' Bt-resistant gene pool.
Graham Head, a researcher with Monsanto, said that current company assessments show that 85%-95% of U.S. Bt corn farmers comply with refuge requirements and at least 91% of Bt cotton growers comply as well.
Genetically altered corn comprised roughly 25% of all corn planted in the United States, while biotech cotton accounts for about 30% of the total crop. Only 4% of U.S. potatoes are genetically altered.
The bacillus thuringiensis produces hard crystalline proteins, which, when consumed by the insect, punch holes in its digestive system, causing it to starve to death over a period of two to three days.
Farmers have used the various Bt proteins as natural insecticides for many years, and the first crop genetically altered to produce its own Bt proteins was licensed for commercial cultivation in 1995.
Different Bt crops use genes from different strains of the bacterium to create different crystalline proteins, or Cry for short. Up for review are Monsanto and Novartis breeds of biotech corn the produce the Cry1Ab protein, Monsanto Bt cotton that produces the Cry1Ac protein, and Monsanto's Bt potatoes that produce the Cry3a protein.
On Oct. 19, the advisory panel will examine the environmental effects of Bt crops and Oct. 20 it will review the possible consequences posed to human health by Bt crops. A final review of the EPA report is expected sometime during the spring of 2001, with EPA expected to release its final rules by mid-2001.