Transgenic plants provoke petition.

Genetically modified crops will have a tough row to hoe if some organic farmers and environmentalists have their way.

On Sept. 16, more than 20 groups and individuals filed a petition with the Environmental Protection Agency in a first-of-its kind bid to rescind approvals of a group of plants genetically engineered to produce a particular pesticide. The agency began limited registrations of the plants in early 1995. This year; farmers planted those transgenic crops, including corn, cotton, and seed potatoes, on more than 3 million acres in the United States.

The critics, including Greenpeace International, the Sierra Club, and the International Federation of Organic Agriculture Movements, also want to block future approvals of similar plants. In the petition, they charge EPA with the "wanton destruction" of what they contend is the world's most important biological pesticide. The opponents fear that some insect pests will develop resistance to the pesticide; in addition, cross-pollination between the transgenic plants and their wild relatives could produce wild plants containing genes for the pesticide, possibly leading to resistance in other insects as well.

The plants at the heart of the controversy have been genetically engineered to manufacture one of a group of natural toxins produced by the bacterium Bacillus thuringiensis (Bt). Organic farmers commonly, treat their crops with the bacterium, which has been registered with EPA as a spray pesticide since 1961, because its toxins have no known detrimental effects on fish, birds, or mammals. Bt toxins also degrade readily in the environment, mainly through exposure to sunlight.

The principal toxins in commercial preparations of Bt are found in protein crystals formed when the bacterium produces spores. The toxins are activated only by digestive enzymes in an insect's gut.

The petitioners contend that the transgenic plants are a threat because they continuously produce massive doses of a modified, already active version of a single Bt toxin, which could lead to the development of resistance in insects within 2 to-10 years. This resistance would make Bt useless, the critics say, forcing farmers to change to harsher chemical pesticides.

Paul Clarke of Greenpeace in New York says the organization considers EPA approvals of transgenic plants to be "an assault upon the genetic diversity of native plants." Field tests of other transgenic crops have resulted in significant migration of the engineered genes into nearby crops or into the transgenics' wild, weedy relatives, he says.

Albert J. Heier, an EPA spokesman, says scientists spent considerable time and effort during the original approval process addressing the potential for development of pesticide resistance. "We used agency experts, as well as outside experts, and we looked at all the data we had," he says.

Heier says registrants of the transgenic Bt plants, typically the companies that developed them, must put together a program that educates growers about how to delay or prevent resistance among pests (SN: 7/8/95, p. 21). Registrants also must monitor insect populations for Bt resistance and submit annual reports to EPA.

Nevertheless, participants in last week's action contend that EPA's efforts have been inadequate. Clarke says that if 90 days pass without a "substantive" response, the petitioners will file suit to force EPA to cancel current registrations of Bt transgenics, as well as hold up future approvals, until the agency completes further study.