There is a potential for the pollen from genetically engineered corn to kill monarch butterfly caterpillars up to 60 yards from the cornfield, according to the results of a study reported in today's Nature magazine. Monarch butterflies migrate each year from central Mexico in the winter to as far north as Minnesota in the summer. The Midwest corn belt is home to about half the U.S. population of monarch butterflies each summer. John E. Losey, Cornell assistant professor of entomology and colleagues from that university in Ithaca, N.Y., have shown that that pollen from genetically modified corn dusted on the leaves of milkweed in the laboratory killed 44 percent of the caterpillars that fed on it.
Monarch caterpillars feed exclusively on milkweed.
Caterpillars that fed on untreated milkweed in the laboratory were unharmed. The genetically modified pollen-fed caterpillars also ate less and grew less than the control group, according to the article. The hybrid corn in question, known as Bt corn, has had genes from the bacterium Bacillus thuringiensis spliced into its genes. This creates a pesticide that is effective against the ravenous European corn borer, a major corn pest. But the Bt corn produces pollen that contains crystalline endotoxin, which is toxic to monarch caterpillars.