Host Selection And Related Compounds In Chemical Communication Of Agrilus Mali Matsumura(Coleoptera: Buprestidae)

The apple buprestid bettle,Agrilus mali Matsumura(Coleoptera:Buprestidae),is one of the most important pests in the Xinjiang wild fruit forests in China.Phloem feeding of larvae,can destroy tissues of transporting water and nutrients,causing withered or dided branches.Adults engage in some maturation feeding on the foliage,and may spread plant pathogens.Because of complex terrains for the wild fruit forests and hidden damage of A.mali,conventional control methods for this pest is ineffective(such as drilling and pesticide injection).Thus,the use of chemical communication of insects in the development of new control strategies can be a better way to solve the problem.In order to determine the composition and contents of host plant volatiles for A.mali and its host choice behaviors,we selected four different host plants of A.mali(i.e.,Malus sieversii,Qin Guan,Huang YuanShuai and Hong Xing),tested the behavioral response of male and female A.mali adults to these plants using Y-tube olfactometer,collected volatiles with two methods(i.e.,dynamic headspace and headspace solid phase microextraction),and analysed the samples with gas chromatography-mass spectrometry(GC-MS).We also determined the components and contents of volatiles from A.mali body and frass.The main results are as follows:(1)The choice rates of A.mali females for Huang YuanShuai was the largest,followed by Hong Xing and Malus sieversii.The choice rates for Qin Guan was the lowest.The choice rates for Huang YuanShuai was significantly different from control,but the choice rates for the other three host plants had no significant differences compared with control.The choice rates for paired host plants showed no significant differences.The choice rates of A.mali males for Qin Guan and Hong Xing were relatively higher,and they were the lowest for Huang YuanShuai.The choice rates for Hong Xing were significantly higher compared with control,the choice rates for the other three host plants had no significant differences when compared with control.The choice rates for Hong Xing was significantly different from those for Qin Guan,but the choice rates for the other paired host plants showed no significant differences.(2)The dynamic headspace method and gas chromatography-mass spectrometry were used to determine the volatiles released from four different host plants of A.mali.The results showed that a total of 72 kinds of volatile compounds were collected from the plants.Among these,we collected 48 volatile components from Malus sieversii,44 from Huang YuanShuai,29 from Qin Guan and 35 from Hong Xing.A total of 14 volatiles were common in the four host plants,and they were mainly esters,terpenes and alcohols.(3)The techniques of dynamic headspace,headspace solid-phase microextraction and gas chromatography-mass spectrometry were used to determine the volatiles released by healthy M.sieversii trees,and these volatiles were compared to those induced by exogenous application of methyl jasmonate(MeJA),mechanical damage and feeding of A.mali adults.The results showed that there were some differences between the two methods in the collection of volatile components.With the use of the dynamic headspace method,we collected a total of 70 volatile compounds,and 54,28,46 and 49 of them were collected from the treatments of control,mechanical damage,application of methyl jasmonate and A.mali feeding respectively.Compared with control plants,there is a relatively large change in volatile contents in the other three treatments,and the volatiles involved mainly included methyl salicylate,caryophyllene,nonanal,?-pinene,linalool,and etc.A total of 58 volatile compounds were collected by the headspace solid phase microextraction method,and the four treatments in the above mentioned order each collected 37,40,32 and 34 volatiles.Compared with control plants,there is a relatively large change in the volatile contents in the other three treatments,and these volatiles mainly included(Z)-3-hexen-1-ol,3-hexenal,4-hexen-1-ol,acetate,?-ocimene,caryophyllene,and etc.(4)Volatiles released from A.mali body were also determined.Meanwhile,the glass rod technique was used to test the response of A.mali adults to the body extracts.The results showed that there were some differences between the two methods in the collection of volatile compounds.Through the hexane extraction method,we collected a total of 29 kinds of volatile compounds,and female and male bodies were found to contain 25 and 19 of them,respectively.Sexual differences involved mainly the volatiles of(Z)-7-hexadecenal,(E)-2-tridecenal,and hexadecane.Using the solid-phase microextraction method,we collected a total of 20 kinds of volatile compounds,and female and male each contained 13 and 14 of them.Significant differences between sexes involved the volatiles of(Z)-3-hexen-1-ol,1-octen-3-ol,and hexadecane.Behavioral tests showed that the male extracts caused excited responses in 60.00% of tested females,whereas the female extracts led to an excitation rate of only 13.33% in males.(5)Volatile components from A.mali frass were determined.The results showed that a total of 46 volatile compounds were collected from the frass of adults and larvae.There were 13 kinds of common volatiles between adults and larvae,which showed some differences in contents.We collected 36 and 23 kinds of volatiles,from the adult and larval frass,respectively.In the adult frass,abundant volatiles included 3-hexen-1-ol,nonanal,methyl salicylate,6-methyl-5-hepten-2-one,and etc.The larval frass contained high contents of 1-octen-3-ol,hexadecane,D-limonene,and etc.