Each year, the larvae of the pink bollworm cause more than $7 million in damage to the U.S. cotton crop. Now, in the first open-field release of a genetically modified insect, entomologists hope to show that genetically engineered versions of this small moth could help control or even eliminate this major pest. Not only could the project protect the nation’s approximately five million hectares of cotton crops, but it could clear the way for the testing of other genetically modified insects as a more effective and environmentally benign alternative to pesticides.

The U.S. Department of Agriculture has approved plans by its scientists to conduct a full field release of the biotech bollworm in the summer of 2005, following several years of tests in enclosed fields. In this trial, the insects will contain only an extra gene that makes them fluoresce under ultraviolet light, allowing researchers to distinguish the laboratory-bred bugs from wild bollworms. “We’re trying to see how the transgenic animals behave in the field,” says University of California, Riverside, entomologist Thomas A. Miller, who led the effort to modify the insects.

In the long run, though, the researchers hope to release moths carrying genes that will kill offspring in the embryonic stage after the altered moths interbreed with wild bollworms. Luke Alphey, a University of Oxford entomologist, developed the requisite genetic technology and has formed a startup, Oxitec, to commercialize it.

Not surprisingly, the biotech bugs have raised red flags among environmentalists who worry about unforeseen consequences of releasing engineered insects. “We’re not terribly good at predicting what happens if you introduce something new into an environment, on a broader ecosystem level,” says Michael Fernandez, director of science at the Pew Initiative on Food and Biotechnology, which published a report last winter on concerns about genetically modified insects. One of the biggest fears: that the new genes might escape into other species, perhaps accidentally eradicating beneficial insects.

The scientists performing the pink bollworm work say that because of the methods used, and because insects tend not to breed across species lines, such an incident is extremely unlikely. “It is an issue, and one has to think about it carefully,” says Alphey. “But there are very low risks.” A test release of moths carrying the embryo-killing genes will not be planned until the researchers find a gene package that works well in moths. Meanwhile, researchers are busy modifying several other insects to control other crop and livestock pests.