Submitted to: Seed Production Research at Oregon State University
Publication Type: Experiment Station
Publication Acceptance Date: February 28, 2009
Publication Date: March 31, 2009
Citation: Gavin, W.E., Banowetz, G.M., Griffith, S.M., Mueller Warrant, G.W., Whittaker, G.W. Short-term effects of chlorpyrifos and other pesticides on earthworm numbers. Seed Production Research at Oregon State University. 2009. p. 77-81. Interpretive Summary: Field studies were conducted to determine whether application of the insecticide to control billbugs in white clover had impact on the activity or densities of the non-traget organism, the earthworm. This was important because earthworms play a positive role in white clover seed production by reducing thatch, recycling crop residues, improving water infiltration, and impacting soil nutrient cycles. In our trials, earthworm densities and activity showed no reduction during observations made 18 and 30 days after the insecticide was applied. Activity reductions did occur during the first week after application, but no lesions were observed on earthworms, and activity returned to that observed in untreated plots within 18 days.
Technical Abstract: Chlorpyrifos is generally used on grasses grown for seed to control billbugs (Sphenophorus venatus confluens) and cutworms (various species), and on other crops for crane fly larvae (Tipula sp.), garden symphyllans (Scutigerella immaculate), and wireworms (Agriotes sp.). The indirect impact of controlling the target species may also adversely effect non-target species such as earthworms. Earthworms reduce thatch (in turf grasses), remove crop residue, improve water infiltration and aeration through their burrows, and play an important role in the nutrient cycle. We conducted field studies to quantify the effect of chlorpyrifos applications on earthworm densities and found no reduction in activity or density 18 and 30 days following treatment. Temporal rate-dependent reductions in activity were observed during the first week following application. These data suggest that real-time field condition applications of both chlorpyrifos alone and in combination with paraquat and MCPA amine, have only temporal effects on these important non-target species.