Selective toxicity of diafenthiuron to non-target organisms: honey bees, coccinellids, chelonus, earthworms, silkworms and fish

Abstract

Diafenthiuron, an insecticide widely used in the management of pests of cardamom and cotton, was assessed for its toxicity-effect on beneficials commonly found in these ecosystems. Diafenthiuron was found to be toxic to honey bees, the prime pollinators of crop plants. Diafenthiuron at the highest tested dose caused 40% mortality to the coccinelid grubs at 48 h after treatment so, diafenthiuron was found to be slightly harmful. Monocrotophos, on the other hand has been found to be a highly toxic pesticide. Diafenthiuron is moderately harmful to the adults of Chelonus blackburni L. The testing was done using the insecticide diafenthiuron. An insecticidecoated vial (scintillation) bioassay was performed. It was found that there was 86.67% mortality in 48 h, at the recommended dose. Diafenthiuron is highly toxic to the silkworm, killing more than 80% of the caterpillars in 24 h, at all the doses tested. Diafenthiuron, even in the highest dose tested, is non-toxic to the earthworm, Perionyx excavatus, which was found to have a 3.33% mortality. As far as fish are concerned, the common carp, Cyprinus carpio L., is found to be highly susceptible to diafenthiuron and even doses 10 times lower than the field dose can kill the fish within 6 h.

Keywords

• coccinellids
• diafenthiuron
• earthworm
• fish
• honey bees
• selective toxicity
• silkworm