Effects Of Body Surface Volatiles Of Diaphorina Citri On The Host Searching Behavior Of Parasitoid Tamarixia Radiata

The Asian citrus psyllid（ACP）,Diaphorina citri Kuwayama（Hemiptera:Liviidae）,which has been found in lots of countries around the world,is a destructive pest of citrus due to its ability to transmit Candidatus Liberibacter asiaticus（CLas）,the causal agent of Huanglongbing（HLB）disease.Thus,ACP management is one of the most important measures to control the spread of HLB.Biological control,with the characteristics of non-polluting,environmental friendly and long-term effectiveness,is currently the most prospect control measures of ACP,and among the natural enemies,Tamarixia radiata（Waterston）（Hymenoptera:Eulophidae）,is a dominant ectoparasitoid parasitoid of ACP.In the present study,we investigated（1）the host choosing behaviour of T.radiata to host volatiles;（2）the composition of ACP surface volatiles;（3）the EAG and Y-tube behavioral response of female T.radiata to the special volatile compounds;（4）sensilla types and distribution of T.radiata antennae.The findings are expected to afford theoretical basis and application support for the utilization T.radiata in D.citri control.（1）ACP host choice of T.radiata.Based on the Y-tube olfactometer test,T.radiata female adults exhibited a significant positive response to the M.paniculata shoots,3^rdinstar,4^thinstar and 5^thinstar nymphs of ACP compared to the blank odour control;but they didn’t prefer neither the 1^stinstar nor 2^ndinstar nymphs.In contrast,the male wasps were not attracted to odors from1^st-5^thinstar ACP nymph.Furthermore,in the Y-tube olfactometer test of different instar comparison,T.radiata did not shown significant preference to the any comparison of the 3^rd,4^thand 5^thinstar nymphs.In the host preference of“single instar nymph”test,T.radiata shown higher parasitization to older instar ACP nymphs comparing with younger instars,the highest parasitization was found to 5^thinstars followed by 4^thand 3^rdinstars.（2）Collection and identification of volatiles from ACP nymphs.Volatiles from the5^thinstars ACP nymphs were collected by the technology of solid-phase microextraction（SPME）and were identified by gas chromatography-mass spectrometry（GC-MS）analysis.Nine chemicals were successfully identified,which belonged to aldehyde,alkane and alcohol including hexanal,heptanal,trans-2-nonenal,tetradecanal,n-tetradecane,n-pentadecane,n-heptadecane,1-dodecanol and 1-tetradecanol.（3）The EAG response of T.radiata female to selected volatile compounds.Results indicated that T.radiata female show positive response to the nine volatile compounds.Moreover,the relative EAG values of T.radiata antennae increased with the increased concentration from 0.01-10μg/μL of trans-2-nonenal,hexanal,heptanal,n-heptadecane and tetradecanal.（4）Five compounds（trans-2-nonenal,hexanal,heptanal,n-heptadecane,tetradecanal）that conducted in EAG dose-response were tested in a Y-tube olfactometer.T.radiata female adults exhibited a significant attraction to tetradecanal at the concentration of 10μg/μL and trans-2-nonenal at 0.01μg/μL when compared with the n-hexane control.However,female T.radiata adults shown no significant preference to tetradecanal at concentrations 0.01-1μg/μL;trans-2-nonenal at 0.1-10μg/μL;and hexanal,heptanal and n-heptadecane at 0.01-10μg/μL.（5）Observation of sensilla on the T.radiata antennae.The sensilla on the T.radiata antennae was observed and identified by SEM.Results indicated that there are five sensilla types on the antennae of T.radiata female,including sensilla chaetica,sensilla trichodea,plate sensilla,basiconic capitates peg sensilla and terminal finger-like sensilla;while four types sensilla on the male T.radiata including sensilla chaetica,sensilla trichodea,plate sensilla and basiconic capitates peg sensilla.Moreover,sensilla trichodea may divided in four subtypes（type 1-4）according to their different external morphology.