Effects of solvent on the toxicity of dimethoate in a honey bee in vitro larval study.

There is increasing interest in the toxicity of pesticides to honey bee larvae. The solubility of pesticides in the artificial diet used to dose larvae is a key issue. There has been no full evaluation of the use of solvents to dissolve pesticides in the larval toxicity test system. Data generated for the toxicity of dimethoate to larvae using 5 and 10% acetone solvent in the diet were similar and close to the toxicity data for adults (LD50 0.1-0.3 µg bee(-1)). With only 1.5% acetone as a vehicle, the toxicity (LD50 0.6-1.14 µg larva(-1)) was lower and closer to published validation data of 1.5-3.1 µg larva(-1) (with some reported data as high as 8.8 µg larva(-1)) generated using dimethoate dissolved in water. This suggests that the solubility of the pesticide in the diet is a key factor in determining its toxicity. Consideration of the solubility of the toxic reference and test items when designing studies is important. The use of higher rates of acetone in the present study more closely represents the true exposure of larvae to pesticides that are not highly soluble in diet. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.