Effect Of Maize Volatiles Induced By Spodoptera Frugiperda On The Behavior Of Mythimna Separata And Ostrinia Furnacalis

When host plants are infested by phytophagous insects,they often release specific volatiles that differ from those of healthy plants.These low molecular weight organic compounds are known as herbivore-induced plant volatiles(HIPVs),and play a crucial role in the complex plant-insect interactions.The invasive pest Spodoptera frugiperda(J.E.Smith)is a violent omnivore and is a major problem in China.It has been demonstrated that the volatiles induced by S.frugiperda on corn have an effect on larval feeding and adult egg laying.However,it is unclear whether the infestation of corn by the larvae of S.frugiperda affects the behavior of native corn pests and whether herbivore-induced maize volatiles mediate this phenomenon.Therefore,in this study,we aimed to investigate the role of herbivore-induced plant volatiles in the host selection of native maize pests Ostrinia furnacalis and Mythimna separata when the maize is infested by S.frugiperda.Overall,these findings provide important insights into the behavioral responses of O.furnacalis and M.separata to herbivore-induced maize volatiles,which could have significant implications for pest management strategies in maize crops.The mainly results as following:1.Impact of S.frugiperda on populations of M.separata and O.furnacalis in field.The impact of S.frugiperda on their populations varies significantly when M.separata and O.furnacalis coexist with S.frugiperd.By day 30 of the experiment,all three pests had entered the third generation of their reproductive period,and the number of pests per plant was 1.73±0.31 and 2.20±0.33 for M.separata and O.furnacalis,respectively,when they existed separately.These numbers were significantly higher than the numbers observed when S.frugiperd were present,especially for M.separata,which were 0 in some treatment groups.These results indicate that S.frugiperda not only have stronger survival and reproductive abilities than native pests,but also affect the survival of native pests.2.Identification of volatiles from normal maize and induced by S.frugiperda infestation.The volatiles from normal maize and those induced by S.frugiperda infestation were identified through(GC-MS).The study found that a total of 20 compounds were detected in maize plants under two different treatments,and compared to normal maize plants,seven new compounds,(E)-2-Hexenal,Isoamyl acetate,(Z)-3-Hexenol acetate,Linalool,β-Caryophyllene,(E)-α-Begamotene and(E)-β-Farnesene were released after feeding on maize plants by S.frugiperda.There were significant differences in the contents of all six compounds except for β-Caryophyllene.While(Z)-3-hexen-1-ol and(3E)-4,8-dimethyl-1,3,7-nonatriene(DMNT)increased,the differences were not significant.α-Pinene,2-Ethylhexanol,Decanal,Nonanal,and α-Cedrene decreased in five compounds,except for Nonanal,where the other four compounds showed significant differences in content.3.Electrophysiological responses of M.separata and O.furnacalis to the herbivoreinduced maize volatiles.Gas chromatography-electrotactile potential(GC-EAD)identified(Z)-3-hexen-1-ol,Isoamyl acetate,α-Pinene,(Z)-3-Hexenol acetate,2-Ethyl-hexanol,Linalool,DMNT,Decanal,β-Caryophyllene and(E)-α-Begamotene as the antennal active ingredients of unmated female M.separata.In addition,(E)-2-Hexenal,(Z)-3-hexen-1-ol,α-Pinene,(Z)-3-Hexenol acetate,2-Ethyl-hexanol,Linalool,DMNT and Decanal were identified as the antennal active ingredients of matted female M.separata.The antennal of unmated female of O.furnacalis responded to(E)-2-Hexenal,(Z)-3-hexen-1-ol,α-Pinene,(Z)-3-Hexenol acetate,2-Ethyl-hexanol,Linalool,DMNT,Nonanal,Decanal,β-Caryophyllene and(E)-β-Farnesene.Additionally,(E)-2-Hexenal,α-Pinene,(Z)-3-Hexenol acetate,Linalool,Nonanal,DMNT,Decanal,β-Caryophyllene and(E)-β-Farnesene were identified as the antennal active ingredients of matted female O.furnacalis.Electroantennogram(EAG)experiments were conducted to determine the antennal responses of O.furnacalis and M.separata to nine different volatile compounds.Results showed that Linalool,(Z)-3-Hexenyl acetate,and Nonanal elicited the strongest EAG responses in female and male antennae of O.furnacalis,while(Z)-3-Hexenyl acetate,2-Ethyl-hexanol,Nonanal,and(Z)-3-Hexenol elicited the strongest EAG responses in male and female antennae of M.separata.4.Behavioural analysis of choice preference of female adults and larvae of O.furnacalis and M.separata for the herbivore-induced maize volatiles.To determine the behavioral responses of these moths to the volatile compounds,Y tube olfactometer assays were conducted.It was found that female O.furnacalis preferred10μg/μL of(E)-β-Farnesene and were repelled by 1μg/μL of Linalool.On the other hand,female M.separata preferred 1μg/μL of(Z)-3-Hexenyl acetate and 0.1 μg/μL of Linalool,while being repelled by 0.001 μg/μL,0.01 μg/μL,and 0.1 μg/μL of(E)-β-Farnesene.Furthermore,larval feeding choice tests were conducted,which revealed that the volatile compound(E)-2-Hexenal had a lure effect on O.furnacalis larvae,while it had a repellent effect on M.separata larvae.