| Spodoptera frugiperda(J.E.Smith),also known as fall armyworm,is a polyphagous,transboundary migratory,and highly reproductive pest native to tropical and subtropical regions of America.With the invasion of China in 2018 and its rapid spread,it has seriously threatened the production safety of many economic crops in China.Plant volatile substances are used as the means of chemical communication between the plant itself and the outside world,It has been proven that there is a very close relationship between plants,herbivorous insects and insect natural enemies.Plants can directly or indirectly defend against herbivorous insects by releasing volatile substances to achieve self-protection.This paper explores the antennae electrophysiology of the common plant volatile substances of Spodoptera frugiperda and its predatory natural enemy,Sycanus croceouittatus;and observation of olfactory behavioral selection of volatile substances by Spodoptera frugiperda and its predatory natural enemy Sycanus croceouittatus;and further analysis of the relationship between the concentration difference of plant volatile substances and their behavioral choices;The predation ability of the natural enemy insect,Sycanus croceouittatus,on the larvae of Spodoptera frugiperda was determined.The main results are as follows:1.The electrophysiological response of the antennae of male and female Spodoptera frugiperda and Eurydema dominulus to different plant volatiles.Both male and female Spodoptera frugiperda showed electrophysiological responses to 8 tested plant volatiles.There were significant differences in the relative EAG response values between different concentrations of the same volatile substance among the 8 volatiles.The relative EAG response values of female Spodoptera frugiperda to(Z)-3-hexen-1-ol,β-caryophyllene and limonene all increased with increasing concentration,while those of males increased significantly with increasing concentration for(Z)-3-hexen-l-ol and benzaldehyde.The male and female adults of Sycanus croceouittatus have different degrees of EAG relative response changes to two volatile substances(cis-3-hexen-l-ol andα-pinene).By changing the concentration of plant volatile substances,the intensity of the effect can be changed.This is manifested as a positive correlation between the concentration of volatile substances and the relative EAG response.2.The olfactory behavioral responses of male and female adults of the Spodoptera frugiperda and Sycanus croceouittatus to different plant volatile substances.The test results of 8 volatile substances showed that the Spodoptera frugiperda had no significant olfactory effect on limonene and cis-3-hexen-l-ol.Among them,methyl salicylate,β-caryophyllene,benzaldehyde and isobutyraldehyde have a repellent effect on female Spodoptera frugiperda,while ethyl caprate and α-pinene have a significant attractant effect.Male fall armyworms have a repellent effect on methyl salicylate,benzaldehyde and isobutyraldehyde,and an attractant effect on β-caryophyllene and ethyl caprate.The olfactory behavior test results of male and female Sycanus croceouittatus are consistent,with only α-pinene having a significant attractant effect.3.Observation of the ultra-microstructure of the antennae of male and female adults of the fall armyworm and yellow-banded stink bug.It was observed that there are 9 types of receptors distributed on the antennae of the Spodoptera frugiperda:Sensilla trichoidea(ST),Sensilla chaetica(SC),Sensilla squamiforma(SSQ),Sensilla auricillica(SAU),Sensilla basiconica(SB),Sensilla styloconica(SS),Sensilla coeloconic(SCO),Sensilla cavitata-peg(SCP)and B?hm’s bristles(BB).There are certain differences in receptor size between male and female adults.There is no significant difference between the antennae of male and female Sycanus croceouittatus,with 3 types of receptors distributed:Sensilla trichoidea(ST),Sensilla chaetica(SC)and Sensilla basiconica(SB).4.The ability of the Sycanus croceouittatus to control Spodoptera frugiperda.The results showed that the average daily predation rate of Sycanus croceouittatus increased with the increase of prey density,and its predation response to the fall army worm was consistent with the Holling Ⅱ model.The 5 th instar nymphs of Sycanus croceouittatus had the strongest predation ability on Spodoptera frugiperda(a/Th=32.571),followed by 4th instar nymphs(24.880).The predation rate of Sycanus croceouittatus was positively correlated with their prey density,while their search efficiency was negatively correlated with their prey density.The adult density of Sycanus croceouittatus interfered with their predation ability,indicating that as the adult density of Sycanus croceouittatus increased,the total predation rate increased but the average predation rate decreased.Following Hassell’s interference response model,E=0.2046 P-0.2462 and interference coefficient(m)is 0.2462.The use of plant volatile substances and natural enemy insects to control pests is currently an urgent means to be promoted.This experiment systematically studied the relationship between the two and Spodoptera frugiperda in order to provide a theoretical basis for the rational use of biological control of Spodoptera frugiperda through green means. |
