Abstract:

Coleophora obducta (Meyrick) (Lepidoptera: Coleophoridae) is a defoliator
of larch and exclusively latent in leaves. This article tested behavioral responses of C. obducta to nine kinds of larch volatile compositions, namely R-α-pinene, S-α-pinene, β-pinene, ocimene, phellandrene, 3-carene, myrcene, camphene and phytol with EAG and Y-tube olfactometer. The results showed that 0.4 mol·L^-1, most volatile compositions had significant EAG responses compared with the blank control(P<0.05), with exception of females to R-α-pinene, males to R-α-pinene and phellandrene. Besides, there existed difference in EAG responses between males and females. Behavioral responses of C. obducta to nine kinds volatile compositions in a series of concentrations of 0.0004, 0.004, 0.04, 0.4, 0.8 mol·L^-1 were also examined with a Y-tube olfactometer. Females were inclined to S-α-pinene, S-β-pinene, phellandrene, 3-carene, and phytol to some extent (P<0.05), and males were inclined to ocimene, myrcene, camphene and phytol to some extent (P<0.05). In order to explore an insect-control agent of exotic host plant volatile components to larva's special habit of feeding latently, we further screened volatile compositions that active to females, and then sprayed them singly to healthy larch seedlings. The result showed that most larvae that fed on the twigs sprayed with the active volatile compositions were dead compared to the blank (P<0.01) with exception of myrcene 0.004 mol·L^-1 which had no significant effect(P>0.05). The phenomenon suggested that volatile compositions might be harmful to larvae, thereinto, S-α-pinene 0.04 mol·L^-1 caused the most larvae dead, which accounted for 86.677% of total number.

Key words: Coleophora obducta, plant volatile composition, EAG responses, behavioral responses, feeding