The suitability of Ostrinia furnacalis (Lepidoptera: Crambidae) eggs for Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae) can be changed by T-ostriniae

This study compared the host specificity of two Trichogramma species on Corcyra cephalonica (Stainton) and Ostrinia furnacalis (Guen,e) eggs. Trichogramma ostriniae Pang et Chen (TO) took more time for oviposition during probing and laying eggs, compared with Trichogramma dendrolimi Matsumura (TD). Furthermore, the proportion of host eggs oviposited actually by TD was lower than that by TO on O. furnacalis eggs, whereas there was no significant difference on C. cephalonica eggs. TO produced more females and total offspring than TD on O. furnacalis eggs. This indicated that O. furnacalis was less suitable for the development of TD, compared with the combination of C. cephalonica and TD or O. furnacalis and TO. Microinjection with 4.0 eq mu l(-1) extract of TO female abdomens induced lower hatchability and longer developmental duration of O. furnacalis egg, whereas the extract from TD prolonged developmental duration only slightly, indicating weak toxicity of TD extract. TD emerged from 72.0 % of O. furnacalis eggs helped by oviposition of TO females irradiated with 800 Gy/h Co-60 for 6 min, of which the intensity produced no TO offspring, whereas only 6.5 % of the eggs were parasitized solely by TD. This indicates that the suitability of O. furnacalis to TD can be increased by the addition of TO parasitization factors.