Study On The Feeding Preference Of The Plecoptera Bilinealis And Its Behavioral Response To Plant Volatile Substances

The Plecoptera bilinealis is a major leaf eating pest of Dalbergia odorifera,a precious tree species in China.It affects the accumulation of core materials of D.odorifera and causes serious economic losses.In recent years,regional outbreaks are serious and control is difficult.In the early stage,the project team found that the food preference of Spodoptera litura larvae existed,and there was little research on the mechanism of this phenomenon.In this study,the 4th instar P.bilinealis were taken as the research object,and the food preference and behavior response to host volatile substances of Spodoptera bilitera larvae were studied.The results of the study hope to preliminarily explore the chemical mechanism of the formation of the food preference of P.bilinealis,and provide a theoretical basis for the rational and effective use of host volatiles to develop attractants and green pest control.The main research results are as follows:(1)The P.blinealis have a preference for feeding on different host plants.The 4th instar P.bilinealis had significant differences in preference to five hosts,namely D.odorifera,Dalbergia tonkinensis,Pterocarpus indicus and Erythrophleum fordii(p<0.05).The daily intake data of the fourth instar P.bilinealis showed that the larvae preferred the tender leaves of D.odorifera,followed by the tender leaves of D.tonkinensis;The 4th instar P.bilinealis fed on different host leaves had significant changes in body weight,average food intake and fecal weight(p<0.05),indicating that the food utilization efficiency was the highest when they fed on D.odorifera.The feeding preference of the 4th instar P.bilinealis to different h ost plants was significantly different,and the most favorite host was D.odorifera.(2)Feeding experience had significant influence on host selection of P.bilinealis.The results showed that the selection index of P.bilinealis fed on D.odorifera or D.tonkinensis by different hosts was significantly different(p<0.05).Among them,after the 4th instar P.bilinealis had feeding experience of D.odorifera,their selection index for D.odorifera leaves(CI=80.74%)was higher than that of the larvae without host feeding experience(CI=65.19%);The selection index of D.odorifera leaves decreased(CI=51.85%)and the selection index of D.odorifera leaves increased(CI=41.48%)after the experience of D.odorifera feeding.Feeding experience has influence on the feeding preference of P.blinealis,and the P.bilinealis with feeding experience of a certain host will increase their preference for feeding on the host.(3)Volatile analysis of most host plants and behavioral response of larvae.The volatile components of D.odorifera leaves were analyzed by GC-MS.30 main plant volatile compounds were obtained from the tender leaves of D.odorifera,and 20 main plant volatile compounds were collected from the old leaves of D.odorifera;There are 17 specific volatiles from tender leaves and 8 specific volatiles from old leaves.The results showed that the selective reaction rate of the 4th instar P.bilinealis to n-hexanal,cinnamaldehyde,farnesene and tetranethyl benzene increased with the increase of concentration,and tetramethyl benzene had the attraction effect only when the concentration reached 10 g/L.At the concentration of 10g/L,when the four compounds were used alone,cinnamaldehyde had the best attraction effect(CI=61.11%),followed by n-hexanal,farnesene and tetramethyl benzene;When the above volatile substances are used in combination at the concentration of 10g/L,the combination of n-hexanal+cinnamaldehyde+farnesene is higher than other combinations(CI=78.89%),which is the combination with the best attraction effect.This study found that the most preferred host of the P.bilinealis is D.odorifera,and its feeding experience will affect its feeding preference.Among the volatile substances in the tender leaves and old leaves of D.odorifera,the components that can attract the P.bilinealis include n-hexanal,cinnamaldehyde,farnene,and tetramethylbenzene,and the attraction effect increases with the increase of concentration.Among them,cinnamaldehyde is the single substance with the best attraction effect,The best combination is n-hexanal+cinnamaldehyde+farnesene.This study is not only of great significance to reveal the internal mechanism of disaster occurrence,but also of great value to the development and comprehensive treatment of its specific attractants.