Effects on Wildlife of At-Planting Corn Applications of Granular Carbofuran

Abstract

Application, at planting, of a granular formulation of the insecticide carbofuran to 195 ha of corn resulted in wildlife mortalities in Frederick County, Maryland, in April and May 1980. Systematic field searches within 96 hours of treatment revealed six dead songbirds (order Passeriformes), five of which contained residues of carbofuran ranging from 1.6 to 17.0 ppm (gastrointestinal tract and liver combined). An American robin (Turdus migratorius) and a mallard (Anas platyrhynchos) were observed exhibiting symptoms consistent with carbofuran poisoning. A dead white-footed mouse (Peromyscus leucopus) found 24 hours posttreatment contained 15.1 ppm carbofuran. The pesticide was detected in 10 of 12 common grackles (Quiscalus quiscula) shot at the site (gastrointestinal tract and liver: f = 0.75 ppm, SE = 0.19), suggesting extensive sublethal exposure among birds feeding in treated fields. Captive house sparrows (Passer domesticus) and red-winged blackbirds (Agelaius phoeniceus) were orally administered carbofuran granules; doses as low as one granule resulted in fatalities with both species. Given the extensive annual use of granular carbofuran (>4 x 106 ha) in the United States, numerous wildlife mortalities are likely. J. WILDL. MANAGE. 48(4):1353-1359 Toxic pesticides are applied to large areas of farmland annually. The corn crop in the United States, for example, amounts to approximately 34 million ha with 11 million ha treated with insecticides (Eichers et al. 1978). When pesticides are applied in populated areas, as occurred in Dutch elm disease treatments (Hickey and Hunt 1960) or, more recently, in pesticide treatments to turf (Stone 1979), wildlife mortalities are observed and reported. Most agricultural land in the United States, however, occurs in sparsely populated areas. With few people searching for dead wildlife in treated fields and considering the rapidity with which carcasses disappear (Rosene and Lay 1963), even if kills were common they would seldom be observed and reported. The objective of our study was to investigate the effects on wildlife of at-planting corn applications of granular carbofuran (Furadan? 10 Granul s), a widely used corn insecticide (Eichers et al. 1978). We thank S. D. Palmeteer and J. A. McCann of the Terrestrial and Aquatic B ol. Lab., U.S. Environ. Prot. Agency, Beltsville, Maryland, for laboratory space and equipment. C. E. Grue, U.S. Fish and Wildl. Serv., Patuxent Wildl. Res. Cent., generously supplied the red-winged blackbirds. We thank C. Bushong, K. R. Barbehenn, and R. R. Stevens for commenting on an earlier draft of this paper. STUDY AREA AND METHODS The study area was in northwestern Maryland (Frederick County), a rural agricultural region. Cropland at the site (405 ha) is privately owned. Corn was the only c op planted at the time of the study, but in previous years some alfalfa and soybeans were grown. Fifteen fields totaling 195 ha were selected for study. The fields J. Wildl. Manage. 48(4):1984 1353 This content downloaded from 157.55.39.223 on Wed, 24 Aug 2016 05:40:50 UTC All use subject to http://about.jstor.org/terms 1354 EFFECTS OF CARBOFURAN ON WILDLIFE * Balcomb et al. were not contiguous but were interspersed with woodlots, hedgerows, fallow fields, turf, and roads. A stream bisected the area. Fieldwork was conducted from 22 April to 16 May 1980. Pesticide Applications Furadan? 10 Granules (10% carbofuran: 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) were applied at planting at the rate of 11.2 kg of product/ ha (1.12 kg active ingredient [a.i.]/ha) to control corn rootworm. Two common methods of planting were used: (1) the soil surface was plowed and disked prior to planting (115 ha), and (2) a no-till technique was used such that planting proceeded over existing soil conditions and surface litter without plowing or disking (80 ha). A White (model 543) six-row planter was used. This apparatus simultaneously plants the corn seed and applies fertilizer and insecticide (the planter opens a narrow furrow [1.5 x 4 cm], and the seed, insecticide, and fertilizer are metered in and a presswheel closes and compacts the furrow). These methods adhere to label directions and are considered typical of most corn in-furrow treatments. The pre-emergent herbicides atrazine (2.24 kg a.i./ha) and metolachlor (2.8 kg a.i./ha) were applied to plowed fields within a few hours of planting. The postemergent herbicide paraquat (0.28 kg a.i./ ha) was similarly applied to no-till areas.