Persistence and Biological Activity of Residues of Granular Insecticides in Organic Soil and Onions with Furrow Treatment for Control of the Onion Maggot (Diptera: Anthomyiidae)

Abstract

studies with the granular insecticides chlorfenvinphos, chlorpyrifos, isofenphos, and terbufos showed that when these are applied properly as in-furrow treatments for the control of the onion maggot in organic soil, good control is obtained of the first generation maggot and that damage caused by infestation by second- and third-generation larvae is significantly reduced. Survival of onion maggots from eggs to larvae was independent of whether the eggs were placed beside the plant or in the leafaxils of the plant. Fonofos, chlorpyrifos, and isofenphos were more persistent than isofenphos in organic soil and, with the exception of chlorpyrifos, all had declined to less than half the original level by the beginning of September. Significant residues of each of the four insecticides were detected in immature bulbs (64-76 d after seeding) with the level of residue being much higher in the roots and outer skin. Ninety-six days after seeding (2 mo before harvest), insecticide residues in bulbs were below the level of detection.