GE Free butterfly…

There has been a notable near miss with the monarch butterfly, a situation that has much to teach about the weaknesses of the U.S. regulatory system. In the spring of 2000, the U.S. media were confronted with a preliminary report in Nature indicating that pollen from Bt corn could kill the larvae of monarch butterflies in laboratory studies. The Nature study was published after several Bt-corn varieties had been approved by the Environmental Protection Agency (EPA) and over 20 million acres of Bt corn were planted in the United States. The big question was why the EPA had not addressed the threat to monarchs before approval of Bt corn. From a scientific standpoint, it is not surprising that a toxin aimed at the European corn borer (moth larvae) would also affect the larvae of the monarch butterfly. The tests required by the EPA prior to approval of Bt crops included a few trials in which Bt toxin was fed to honeybees and lacewings, among other organisms, but did not include tests on any non-pest moths and butterflies (EPA, 1997).

The storm of publicity eventually forced the government to do a thorough risk assessment of the threat. To its credit, the USDA organized aworkshop of scientists with expertise in the many areas needed to evaluate the monarch issue and asked them to generate a multi-disciplinary research program that would address the risks. It established a multi-stakeholder advisory committee to formulate a set of coordinated research projects to determine whether Bt corn is lethal to monarchs under field conditions. The department also provided funds—as did industry—to support the research. The results of the studies were published in five papers in September 2001 in the online version of the Proceedings of the National Academy of Sciences (PNAS). (Hellmich
et al., 2001; Oberhauser et al., 2001). The major conclusion of the research was that only one of several Bt-corn varieties (Event 176) approved and planted for use in the United States produced high enough levels of Bt toxin in pollen to be lethal to butterfly larvae. Fortunately, that variety of genetically modified corn did not sell well and was not widely planted. Pollen from the two types of Bt corn which account for most of the Bt-corn acreage (Mon 810 and Bt 11) produce relatively low amounts of toxin and pose negligible risk to monarchs. If Event 176 had turned out to be popular, monarchs
could have been in serious jeopardy. It was just luck break and not governmental controls that protected the monarch butterfly. However, these studies did not completely resolve the issue. Some scientists have pointed out that monarchs consume tissue from anthers—the pollen-producing parts of the corn flower—as well as pollen from Bt corn as reported by Pleasants et al. (2001) and Sears et al. (2001). Since anthers have been shown to contain considerably more toxin than pollen, these scientists believe that the PNAS studies based on pollen alone may seriously underestimate the toxin dose consumed by monarch larvae in corn fields.