Comparative Study Of Oviposition Deterring Pheromone Of The Asian Corn Borer, Ostrinia Furnacalis (Lepidoptera: Crambidae) To The European Corn Borer, O.nubilalis

The Asian corn borer,Ostrinia furnacalis(Lepidoptera:crambidae) and the European com borer,O. nubilalis(Lepidoptera:crambidae) were among the most important pests of corn and cotton,leading to a huge economic loss in agricultural production.The mutual relationships among host plant,herbivore and natural enemy mediated by methanol and oviposition deterring pheromones(ODPs) were of great importance for pest control.1.Chemical identification of ODPs from extracts of larval frass,egg masses and midgutThe major ODPs of the extracts from larval frass,egg masses and midguts of O.furnacalis and O. nubilalis fed on an artificial diet were identified by GC and GC-MS.The major components in extracts of larval frass and egg masses of O.furnacalis were fatty acids(FAs).In contrast,the major chemicals in extract from larval frass of O.nubilalis were a blend of FAs and fatty acid methyl esters(FAMEs),and those from egg masses of O.nubilalis were FAMEs.These FAs were also presented in artificial diet,but the content was low.The major chemicals in extract from larval midgut of O.furnacalis were FAs,the content increased gradually from 1^st to 4^th instar,and decreased in the 5^th instar.2.ODPs perception in O.furnacalisFour fatty acids,C14:0,C16:0,C18:0 and C18:1,and their corresponding methyl esters,could elicit evident EAG responses from both sexes of O.furnacalis.Among four binary blends mixed by a fatty acid and its corresponding methyl ester,C 14:0 and C 14:0ME,C 16:0 and C 16:0ME activated two different types of olfactory receptors in males.In contrast,C18:0 and C18:0ME,C18:1 and C18:1ME stimulated the same type of olfactory receptors in males and females.3.The biological activities of O.furnacalis to extract from egg masses or larval frassThe biological activities of O.furnacalis to extract from egg masses or larval frass were investigated by EAG analyses and bioassay tests in laboratory.Extracts from larval frass or egg masses at different concentrations could elicit significant higher EAG response from O.furnacalis gravid female than solvent. The extract from larval frass could trigger EAG responses from both sexes,and the values tested before copulation was different from those observed after copulation.The extract from larval frass could deter ovipositon,but did not affect the egg number in each egg mass.4.The influences of diets to O.furnacalis ODPs and their mechanismsThe major components and compositions of ODPs from frass of O.furnacalis larvae fed on an artificial diet with or without methanol were compared.It was found that FAMEs were present in frass from larvae on the methanol-contained diet but not from larvae on the methanol-free diet.In order to confirm our hypothesis that these FAMEs were originated from methanol detoxication,we determinedα-NA hydrolysis esterase activity,and found dietary methanol induced higher esterase activity in first-, second- and third-instar larvae.In addition,in vitro test revealed that a crude enzyme solution from larvae could synthesize FAMEs from corresponding fatty acid and methanol,but the conversion efficiency was low.These demonstrated that FAMEs of larval frass originated from the non-oxidative metabolism for methanol.