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Effects on litter‐dwelling earthworms and microbial decomposition of soil‐applied imidacloprid for control of wood‐boring insects
Author(s) -
Kreutzweiser David P,
Good Kevin P,
Chartrand Derek T,
Scarr Taylor A,
Holmes Stephen B,
Thompson Dean G
Publication year - 2008
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.1478
Subject(s) - eisenia fetida , imidacloprid , decomposer , microcosm , litter , earthworm , biology , toxicology , zoology , plant litter , agronomy , pesticide , ecosystem , ecology
BACKGROUND: Imidacloprid is an effective, systemic insecticide for the control of wood‐boring insect pests in trees. Systemic applications to trees are often made by soil injections or drenches, and the resulting imidacloprid concentrations in soil or litter may pose a risk of harm to natural decomposer organisms. The authors tested effects of imidacloprid on survival and weight gain or loss of the earthworms Eisenia fetida (Savigny) and Dendrobaena octaedra (Savigny), on leaf consumption rates and cocoon production by D. octaedra and on microbial decomposition activity in laboratory microcosms containing natural forest litter. RESULTS: Dendrobaena octaedra was the most sensitive of the two earthworm species, with an LC 50 of 5.7 mg kg −1 , an LC 10 of about 2 mg kg −1 and significant weight losses among survivors at 3 mg kg −1 . Weight losses resulted from a physiological effect rather than from feeding inhibition. There were no effects on cocoon production among survivors at 3 mg kg −1 . The LC 50 for E. fetida was 25 mg kg −1 , with significant weight losses at 14 mg kg −1 . There were no significant effects on microbial decomposition of leaf material at the maximum test concentration of 1400 mg kg −1 . CONCLUSION: The results indicate that, when imidacloprid is applied as a systemic insecticide to the soil around trees, it is likely to cause adverse effects on litter‐dwelling earthworms if concentrations in the litter reach or exceed about 3 mg kg −1 . Copyright © 2007 Her Majesty the Queen in the Right of Canada, Canadian Forest Service. Published by John Wiley & Sons, Ltd.