Carbofuran Persistence in Cornfield Soils1

Abstract

Field and laboratory studies showed that soil moisture is a very important factor in carbofuran persistence when this insecticide is used for control of larva] corn rootworms. Carbofuran rapidly disappeared from the surface soil layer of two cornfields after the first large rainfall; this disappearance occurred within 2 and 10 weeks after application, respectively. No carbofuran was detected below the 7.5-cm soil layer 22 weeks after application. In the laboratory, carbofuran applied as Furadan 10G to high-moisture soils also disappeared rapidly, suggesting degradation rather than leaching to lower soil layers. Carbofuran disappearance was slightly slower in one of four soils tested, and all the soils showed a 5- to 7-day lag time that strongly indicated microbial degradation. The rate of carbofuran (as Furadan 10G) disappearance in laboratory experiments increased with higher soil moisture levels. A laboratory study showed that carbofuran does leach through soil, but carbofuran from the formulated product was less susceptible to leaching than the technical material.