EAG AND ORIENTATION TESTS ON THE PARASITOID LYSIPHLEBIA-JAPONICA (HYM., APHIDIIDAE) TO VOLATILE CHEMICALS EXTRACTED FROM HOST PLANTS OF COTTON APHID APHIS-GOSSYPII (HOM., APHIDAE)

Volatile chemicals from the four summer host plants of cotton aphid Ap his gossypii were extracted and identified, and the behavioural and EA G responses of the parasitoid Lysiphlebia japonica to these volatile c hemicals were also studied. According to GC-MS data analysis and authe ntic samples, 21 volatile compounds were finally confirmed from cotton extract: and 17, 23 and 24 compounds from cucumber, pumpkin and towel gourd extracts, respectively. There are significant differences in co mponents among the four plants. Cotton volatiles contain quantities of terpenes, most of which are monoterpenes and sequiterpenes such as my rcene, beta-caryophellene and alpha-humulene, while the other three me lon plants contain more short chain aldehydes, alcohols, acids, acetat es and their derivatives. Benzaldehyde was not found in cotton leaf ex tracts, however, it was found in all the three melon plant leaves. Amo ng the four host plants of cotton aphid, only cotton leaves (intact) a ttracted to the parasitoids, and the parasitoids did not express any m ore interest to the three melon plants. The two-odour-choice tests dem onstrated that the mechanical damaged cotton leaves and the aphid-hone ydew-plant leaf complex were more attractive to the parasitoids than t he intact ones. These phenomena agree well with the EAG results and th e field observation, i.e. female L. japonica showed stronger EAG and b ehavioural responses to cotton leaf extract than to the other three pl ant extracts.