2-Plants: Scientists fear new threat to butterflies from Bt corn

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TITLE:  Scientists fear new threat to butterflies from Bt corn
SOURCE: Reuter
DATE:   September 14, 2001

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Scientists fear new threat to butterflies from Bt corn

WASHINGTON - Four experts on biotech crops and monarch butterflies have 
urged the Environmental Protection Agency to renew Bt corn registrations 
for only one year and to investigate a new risk the plant may pose to the 
orange-and-black butterflies. The four scientists at Iowa State University, 
Cornell University and the University of Minnesota were among more than a 
dozen others who recently authored papers for the National Academies of 
Science on the risk to monarch caterpillars of windblown pollen from 
genetically engineered Bt corn.

Bt corn is a variety engineered to produce the pesticide Bacillus 
thurigiensis, which protects growing corn plants from destructive pests. 
The scientific papers showed little, if any, risk from Bt corn pollen eaten 
by the butterflies, but questioned whether there was danger from a plant 
tissue known as corn anther.

The Environmental Protection Agency is mulling the proposed renewal of 
several Bt corn and cotton registrations that expire on Sept. 30. The 
varieties were first approved by the EPA six years ago. But some of the 
same research scientists told the EPA that a licensing decision now would 
be "premature" because more studies are needed to determine the risk for 
caterpillars that eat Bt pollen and corn anther.

"The presence of anthers on milk weeds is of considerable importance 
because of the higher concentrations of Bt toxins that they contain," said 
John Losey, an entomologist at Cornell University. Losey, along with John 
Obrycki and Laura Jesse of Iowa State University and Karen Oberhauser of 
the University of Minnesota, urged the EPA to take a closer look at the 
risk of corn anthers.

Unpublished field studies conducted in Iowa cornfields last summer showed a 
50 percent lower survival rate for monarch caterpillars which ate a mixture 
of Bt pollen and anther, the scientists said in a letter to the EPA, dated 
Sept. 11. "We urge, at the very least, that the registrations of Bt corn be 
limited to one year," they said. In the meantime, the agency should require 
new research on the risk of corn anthers and review all data again next 
year, the scientists said.

The biotech industry has pressed for renewal of the EPA registrations, 
contending that the benefits of Bt crops far outweigh any risks. The set of 
National Academies of Science papers found there was less than a 2 percent 
chance of a monarch caterpillar being exposed to Bt corn pollen.

The risk is low because the plants shed pollen during a brief 10-day 
period, which must coincide with the dates when the monarch larvae are 
present, according to the authors. Reducing the risk, too, is the fact that 
only 19 percent of U.S. corn fields were planted with Bt varieties this 
year.



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