William Lamp, Associate Professor
Department of Entomology
4112 Plant Sciences Building
University of Maryland
College Park, MD 20742
Non-target effects of transgenic corn debris in streams: The changing picture of risk assessment
ABSTRACT: The presentation will describe the background and current results of our work through the USDA-BRAG Program on ecological risk assessment. With the widespread deployment of genetically-modified (GM) crops for the management of insect pests, leaves with the plant incorporated protectants (PIPs) will enter streams and ditches through wind dispersal. Since 2005, we have been investigating the risk potential for exposure and hazard effects of Bt proteins in corn plant debris on aquatic invertebrates in running waters. We initially discovered that stream invertebrates were not exposed to the Bt protein in corn leaves. Although the corn expressed Bt in the leaves at harvest, no bioactivity of Bt was found after two weeks of exposure to the ground or to the stream water (see Jensen et al. 2010). We also measured non-target effects in laboratory experiments, and found no effect on two caddisfly species (which are closely related to Lepidoptera, the target of the Bt protein in corn). We did, however, find a negative effect on a crane fly species as well as an isopod species. We explained this effect by a "tissue-mediated effect", in which the presence of Bt in the leaf during the growing season altered the physical and chemical characteristics of the leaf. In a separate study, we also measured leaf decomposition rates of Bt and non-Bt corn leaf debris, and found little evidence of a negative impact of Bt corn on streams (Swan et al. 2009). We have additional manuscripts in preparation to continue the story. Most importantly, we have discovered that the Bt proteins in the current, popular variety based on “SmartStax” with 6 Bt genes persists in the environment for up to five months, so exposure to invertebrates is assured. Based on the long persistence of Bt in the environment, our current research focuses on three perspectives of risk assessment:
1. Refine protocols and test PIPs (plant incorporated protectants) using artificial food suitable for aquatic invertebrates that are adapted for shredding plant debris. We have developed a means to adhere a potential toxin onto food to force aquatic invertebrates to feed on the toxin under water (see Gott et al. 2014). We intend to continue the development of the artificial diet using appropriate species of invertebrates that feed by shredding their food.
2. Perform a landscape-level assessment of GM versus non-GM crops on the running water ecosystems draining cropland. Our work on ecosystem-level testing has not used whole streams as experimental replicates. We intend to locate paired agricultural streams (or ditches) that have not been exposed to Bt crops, and then introduce Bt and non-Bt corn debris to compare whole ecosystem effects in a BACI design.
3. Measure degradation rates of PIPs across genes, varieties, and post-harvest crop management. We believe that how farmers handle crop debris after harvest may reduce the persistence of the Bt protein, and so reduce the potential for exposure to aquatic invertebrates. We are testing various ways to incorporate the crop debris into the ground with tillage.
11:30 AM - 12:25 PM
Kottman 244 (Columbus)
121 Fisher Auditorium (Wooster)