The relative toxicities of insecticides to earthworms of the Pheretima group (Oligochaeta)

Abstract

An artificial soil test was used to determine the LC₅₀ values of carbaryl, chlorpyrifos, imidacloprid, cyfluthrin and fipronil against earthworms of the Pheretima group. For a 24-h interval, carbaryl was the most toxic to earthworms (LC₅₀ = 77 mg kg⁻¹), followed by imidacloprid (155 mg kg⁻¹), cyfluthrin (351 mg kg⁻¹), chlorpyrifos (390 mg kg⁻¹) and fipronil (>8550 mg kg⁻¹) as the least toxic. For the 48-h and 7-day intervals, imidacloprid was the most toxic to earthworms (LC₅₀ = 5 mg kg⁻¹ and 3 mg kg⁻¹ respectively), followed by carbaryl (16 mg kg⁻¹; 9 mg kg⁻¹), cyfluthrin (128 mg kg⁻¹; 110 mg kg⁻¹), chlorpyrifos (330 mg kg⁻¹; 180 mg kg⁻¹) and the least toxic was fipronil (>8550 mg kg⁻¹ both intervals). The surface application rates required to achieve these values are compared with the rates recommended for the control of turfgrass pests. © 2002 Society of Chemical Industry