Insecticidal effects of 4-hexylresorcinol on the lesser mulberry snout moth, Glyphodes pyloalis Walker

Abstract

Insect phenoloxidase (EC 1.14.18.1) is the key enzyme in the development and immunity of insects, and its inhibition provides a new target for pest control. The Glyphodes pyloalis Walker is an important pest of mulberry trees in north of Iran and this pest interferes with the sericulture by feeding on mulberry leaves. In this investigation of alternative insect control agents, we have bioassayed 4-hexylresorcinol against G. pyloalis under laboratory conditions. Lethal dose (LD₅₀) for the last instar larvae was estimated as 5.03 g/l after 96 h exposure. Also, the effects of 4-hexylresorcinol concentrations on glutathione S-transferase and phenoloxidase activities were measured, and the results showed that by increasing the concentration of 4-hexylresorcinol the activity of both enzymes is decreased. The IC₅₀ of quercetin, kojic acid and 4-hexylresorcinol on haemolymph phenoloxidase activity, partially purified using gel filtration, was 7.39, 25.98 and 4.35 μM, respectively. The inhibitory potency of 4-hexylresorcinol was 5.03- and 1.5-fold higher than kojic acid and quercetin, respectively. Also, optimal pH for the haemolymph phenoloxidase was 7.

Keywords:

• IC₅₀
• LD₅₀
• phenoloxidase
• 4-hexylresorcinol
• glutathione S-transferase