Effects of fungicides and insecticides on feeding behavior and community dynamics of earthworms: Implications for casting control in turfgrass systems

▶ We examined impact of pesticides on earthworm behavior in the lab and in the field. ▶ Single application of Sevin and Merit significantly inhibited earthworm feeding. ▶ Pesticide toxicity to earthworms increased with increasing frequency of application. ▶ In the field, multiple applications of T-methyl and Sevin reduced earthworm activities. ▶ Earthworm surface activity in the turf may be temporarily managed via applying pesticides. Earthworms play important roles in sustaining turfgrass systems through enhancing soil aeration, water filtration, and thatch mixing and decomposition. However, high surface activities of earthworms can lead to uneven playing surfaces, soil erosion and new niches favorable to weed invasion in the playing area of a golf course. Shifts from highly toxic and persistent to less toxic and easily degradable pesticides have been suggested to be largely responsible for high earthworm activities observed in turf systems worldwide. In this study, we examined the impact of fungicides and insecticides on earthworm behavior in controlled environments and on the dynamics of earthworm community in the field. Single application of insecticides Sevin (carbaryl) and Merit (imidacloprid) at the manufactures’ suggested doses significantly inhibited earthworm feeding activity for at least three weeks without leading to any earthworm death. Fungicides did not show significant toxicity to earthworms when applied only once, but their toxicities increased as application frequency increased. Consecutive weekly applications of Sevin, Merit and T-methyl for four times led to earthworm mortality of 35, 45 and 80%, respectively. In the field, six consecutive weekly applications of T-methyl and Sevin significantly reduced the abundance and biomass of earthworms with suppressive effects lasting for at least 6 weeks after the chemical application was terminated. Taken together, these findings suggest that the surface activities of earthworms in turfgrass systems may be managed through moderate application of pesticides at peak periods of earthworm activities.