title: Genetically engineered crops and pesticide use in U.S. maize and soybeans.
abstract: The widespread adoption of genetically engineered (GE) crops has clearly led to changes in pesticide use, but the nature and extent of these impacts remain open questions. We study this issue with a unique, large, and representative sample of plot-level choices made by U.S. maize and soybean farmers from 1998 to 2011. On average, adopters of GE glyphosate-tolerant (GT) soybeans used 28% (0.30 kg/ha) more herbicide than nonadopters, adopters of GT maize used 1.2% (0.03 kg/ha) less herbicide than nonadopters, and adopters of GE insect-resistant (IR) maize used 11.2% (0.013 kg/ha) less insecticide than nonadopters. When pesticides are weighted by the environmental impact quotient, however, we find that (relative to nonadopters) GE adopters used about the same amount of soybean herbicides, 9.8% less of maize herbicides, and 10.4% less of maize insecticides. In addition, the results indicate that the difference in pesticide use between GE and non-GE adopters has changed significantly over time. For both soybean and maize, GT adopters used increasingly more herbicides relative to nonadopters, whereas adopters of IR maize used increasingly less insecticides. The estimated pattern of change in herbicide use over time is consistent with the emergence of glyphosate weed resistance.
authors.affiliation: Department of Agricultural Economics, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Edward D
authors.initials: ED
authors.lastname: Perry
authors.affiliation: Department of Economics, University of Virginia, Charlottesville, VA 22904, USA.
authors.forename: Federico
authors.identifier: 0000-0002-3967-1659
authors.initials: F
authors.lastname: Ciliberto
authors.affiliation: Department of Agricultural, Food, and Resource Economics, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Hennessy
authors.affiliation: Department of Economics and Center for Agricultural and Rural Development, Iowa State University, Ames, IA 50011, USA.
authors.forename: GianCarlo
authors.initials: G
authors.lastname: Moschini
mesh_terms: D018556:Crops, Agricultural / Q000187:drug effects / Q000235:genetics*; D004777:Environment; D005818:Genetic Engineering; D053209:Herbicide Resistance / Q000235:genetics; D006540:Herbicides / Q000009:adverse effects; D006801:Humans; D007306:Insecticides / Q000009:adverse effects; D010575:Pesticides / Q000009:adverse effects*; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D013025:Glycine max / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D003313:Zea mays / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development
chemical_list: D006540:Herbicides; D007306:Insecticides; D010575:Pesticides
keywords: Agriculture economics; GMOs; genetically engineered crops; maize; pesticides; soybeans