Insecticides (dimethoate and lambda-cyhalothrin) for soybean aphid control – are they toxic to earthworms? Evidence from laboratory and field bioassays

Abstract

Whalen, J. K., Benslim, H. and Vanasse, A. 2012. Insecticides (dimethoate and lambda-cyhalothrin) for soybean aphid control – are they toxic to earthworms? Evidence from laboratory and field bioassays. Can. J. Soil Sci. 92: 751–758. Outbreaks of the exotic soybean aphid (Aphis glycines Matsumura) cause significant yield loss of soybean [Glycine max (L.) Merr.] grown in North America. This study assessed the toxicity of dimethoate and lambda cyhalothrin, recommended to control soybean aphid, to earthworms, a non-target organism present in soybean fields. Laboratory bioassays showed the lethal and sub-lethal concentrations of dimethoate and lambda cyhalothrin to adult Eisenia fetida (Savigny) and their offspring. The most sensitive toxicity endpoint was adult E. fetida growth rates, which had a half maximal effective concentration (EC50) of 6.39 mg active ingredient (a.i.) kg−1 soil for dimethoate and 5.41 mg a.i. kg−1 soil for lambda cyhalothrin after 28 d exposure. The field bioassay was done on two comme...