Insecticidal Effect of Water Extract of Oleander (Nerium indicum) against the Larvae of Enmonodia vespertilio Fabriciu

[Objective] The paper was to study the insecticidal effect of water extract of oleander （Nerium indicum） against the larvae of Enmonodia vespertilio Fabriciu. [Method] Through feeding experiment on the larvae of E. vespertilio, the insecticidal effect of water extract of oleander against the larvae was studied. [Result] The 1/20-1/200 times water extract of dry leaf weight of oleander had better insecticidal effect against the larvae of E. vespertilio, and the feeding mortality rate reached 100%. [Conclusion] The paper provided reference for development of new botanical pesticides with high efficiency, environmental protection and low carbon.

Taste Adaptation of Helicoverpa armigera Larvae to Azadirachtin and Its Physiological Mechanism

Dual-choice behavioral assays and electrophysiological tip-recording technique were used to investigate the taste adaptation of different diet-experienced frith instar larvae of Helicoverpa armigera to azadirachtin. The behavior test showed that the larvae reared with normal artificial diets were highly deterred by aza- dirachtin. However, the larvae reared with the artificial diets containing low concentration of azadirachtin showed insensitivity to asadirachtin. The electrophysiological tests showed that there was a changed responsiveness in the deterrent neuron responding to asadirachtin in the lateral sensilla styloconica of different diet-experienced larvae. It indicated that there was a taste adaptation to azadiraehtin in different diet-experienced larvae of H. armigera and this taste adaptation was correlated with desensitization of related taste neurons.

Effects of mummy consumption on fitness and oviposition site selection on Harmonia axyridis

Intraguild predation(IGP)has been commonly reported between predators and parasitoids used as biological control agents as predators consuming parasitoids within their hosts.However,the effect of parasitoid-mummy consumption on the fitness of the predator and subsequent oviposition site selection have not been well studied.In our study,we conducted two laboratory experiments to examine the influence of Aphidius gifuen-sis Ashmead(Hymenoptera:Braconidae)mummies as prey on fitness and subsequently oviposition site selection of Harmonia axyridis(Pallas)(Coleoptera:Coccnellidae).Re-sults indicate that when H.aryridis was reared on A.gifiuensis mummies only,its larval development was prolonged,and body weight of the 4th instar larvae and newly emerged adults,and fecundity decreased.Moreover,H.axyridis did not exhibit oviposition pref-erence on plants infested with unparasitized aphids or aphids parasitized for shorter than 9 days.However,compared with plants with mummies(parasitized≥9 days),H.axryridis laid more eggs on plants with unparasitized aphids.In contrast,H.axryridis previously fed with A.gifuensis mummies did not show a significant oviposition preference between plants with unparasitized aphids and those with mummies(parasitized≥9 days).Overall,our results suggest that mummy consumption reduced the fitness of H.axyridis.Although H.axyridis avoided laying eggs on plants with A.gifuensis mummies,prior feeding ex-perience on A.gifuensis mummies could alter the oviposition site preference.Thus,in biological control practice,prior feeding experience of H.axyridis should be carflly considered for reduction of IGP and increase of fitness of H.axyridis on A.gifuensis.