Primary Study On The Host Search Mechanism Of Bamboo Shoot Wireworms,Melanotus Cribricollis

The bamboo shoot wireworm,Melanotus cribricollis?Coleoptera: Elateridae?is the most notorious subterranean pest in Southern China.The larva of M.cribricollis could damage the bamboo shoots of a lot bamboo species,such as Phyllostachys praecox,P.prominens and P.pubescens,etc.The damage of the wireworms caused obvious decrease of production and quality of bamboo shoot,and seriously restricted natural regeneration of bamboo forest.It was very difficult to monitor and control wireworms because they lived indiscoverable in the soil,and the effective and convenient control techniques were required.Plant volatiles are important signal chemicals transmitting information between plants and insects.Attractants developed by plant volatiles have been widely used in the practice of pest control,but there are few studies on attractants towards belowground pests.In present study,aimed at the control of bamboo wireworms,M.cribricollis,the volatiles of host plants such as bamboo shoots were collected and identified,and the behavioral responses of bamboo shoot wireworms towards different foods and plant volatiles were tested.In addition,the typology,number,placement and function of head surface sensilla of M.cribricollis larva were observed with the comprehensive methods of chemical ecology and behavioral ecology.The mainly results are summarized as follows:?1?Wireworms could be attracted by germinated maize and wheat seeds,bamboo shoots,oatmeal and CO₂ emissions,and wireworms preferred significantly to the fresh bamboo shoots.There was no significant difference in the effect of attracting wireworms among different weights of bamboo shoots?x²=0.576,P>0.05?,and the concentration of CO₂ has a significant effect on the orientation behavior of wireworms?x²=7.945,P<0.05?.Our results confirmed that plant volatiles played an important role in the foraging behavior of wireworms.?2?A total of 40 compounds emitted from bamboo shoots were tentatively identified by two methods including solid phase micro-extraction?SPME?and dynamic headspace absorption?DHA?coupled with GC-MS.Forty-eight volatile compounds emanating from maize and wheat seedlings were identified using SPME coupled with GC-MS.The main components in the bamboo shoot volatiles were 1-tridecene?64.04%?,1R-?+?-?-pinene?28.65%?,?-humulene?12.33%?,3-ethyl-2,5-dimethyl-3-hexene?11.80%?,cedrene?4.67%?,?-caryophyllene?2.01%?etc.The important components in the seedllings of maize root were 1,2-benzenedicarboxylic acid-diisooctyl ester?27.92%?,tetradecanal?24.34%?,heptacosane?15.65%?etc.The higher relative components in the seedllings of wheat root were caprolactam?30.29%?,hentriacontane?15.64%?,triacontane?12.23%?and nonacosane?9.09%?.?3??-humulene and?E?-hex-2-enal showed be attractive significantly towards bamboo shoot wireworms,and ?-humulene was more attractive than?E?-hex-2-enal at the same concentration.?-pinene,?-caryophyllene and?E?-non-2-enal had no significant attractive effect on bamboo wireworms.Green leaf volatile,?E?-hex-2-enal had no significant synergistic effect on ?-humulene.The mixture of ?-humulene and?E?-non-2-enal has no obvious attractive effect on wireworms.The concentration of?-humulene and?E?-hex-2-enal had a significant influence on the orientation behavior of wireworms.?4?The results of scanning electron microscopy showed that four types of sensilla were recorded in antennae including sensilla chaetica,sensilla basiconica,hook sensilla and dick-shape sensilla,and three type of sensilla,sensilla basiconica,sensilla coeloconica and sensilla ampullaceal were found in maxillary palp,and seven types of sensilla were observed on labial palp surface including sensilla basiconica,sensilla coeloconica,sensilla ampullaceal,sensilla trichodea,sensilla processus mastoideus,sensilla groove and sensilla dumbbell.The results laid the foundation for revealing the function of the larvae head sensilla in the foraging process of wireworms.We initially screened the two kinds of active compounds that showed be attractive towards bamboo wireworms,and confirmed that plant roots volatiles played an important role in the host foraging process of belowground herbivorous insects.On the one hand,our findings provide important information for host plant identification and search mechanism of belowground phytophagous insects in the soil environment.On the other hand,we could provide theoretical support for the development of highly effective attractants for wireworm control.