Corn (Zea mays L.) that has been genetically engineered to produce the Cry1Ab protein (Bt corn) is resistant to lepidopteran pests. Bt corn is widely planted in the midwestern United States, often adjacent to headwater streams. We show that corn byproducts, such as pollen and detritus, enter headwater streams and are subject to storage, consumption, and transport to downstream water bodies. Laboratory feeding trials showed that consumption of Bt corn byproducts reduced growth and increased mortality of nontarget stream insects. Stream insects are important prey for aquatic and riparian predators, and widespread planting of Bt crops has unexpected ecosystem-scale consequences.

E. J. Rosi-Marshall*^†

+ Author Affiliations

1. *Department of Biology, Loyola University Chicago, Chicago, IL 60626;
2. ^‡Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556;
3. ^§School of Public and Environmental Affairs, Indiana University, Bloomington, IN 47405; and
4. ^¶Department of Zoology and Center for Ecology, Southern Illinois University, Carbondale, IL 62901-6508

1. Communicated by Gene E. Likens, Institute of Ecosystem Studies, Millbrook, NY, July 31, 2007 (received for review March 5, 2007)