Survey On Occurrence And Damage Of Banana Weevils In Hainan And Preliminary Study On Host-selection By Banana Pseudostem Weevil, Odoiporus Longicollis (Olivier)

Banana is an important fruits in tropical and subtropical regions of the world, and banana weevils are important pest species of banana. Systematic survey on occurrence and damage of banana weevils in Hainan was undertaken, and preliminary study had been made on host-selection by banana pseudostem weevil, Odoiporus longicollis (Oliver) (Coleoptera:Curculionidae) to probe into relationship between banana pseudostem weevil and banana.The survey results showed that O. longicollis was the most major pest, followed by banana corm weevil, Cosmopolites sordidus (Germar) (Coleoptera:Curculionidae), and Polytus mellerborgi (Boheman) (Coleoptera:Curculionidae), which was a new record species in China. The damage of P. mellerborgi was the lightest. O. longicollis, C. sordidus and P. mellerborgi were widely distributed in Danzhou, Changjiang, Dongfang, Ledong, Lingao, Chengmai, Haikou, Wenchang, Qionghai, Sanya and Baisha banana plantations. There were differences on the occurrence extent banana weevils among different regions, and also among different banana plantations of the same region.Solid phase microextraction (SPME) was applied to extract volatiles from banana pseudostems at four physiological status (including fresh pseudostem, rotten pseudostem without beetle eating, beetle-eaten and rotten pseudostem, beetle-eaten pseudostem without rotting) and from female and male O. longicollis, and the extracted volatiles were analyzed using gas chromatography-mass spectrometry (GC-MS). The results showed that a total of 10 components had been identified in fresh pseudostem and beetle-eaten and rotten pseudostems, and a total of 11 components in rotten pseudostems without beetle eating and beetle-eaten pseudostems without rotting respectively. Alloocimene was the common component from banana pseudostems at four physiological status, and its relative content (9.86%) was higher in rotten pseudostems without beetle eating than in others. There were hydrocarbons and esters in all the four kinds of banana pseudostems and the relative content of hydrocarbons was the highest in fresh pseudostems, representing 87.14% of the total peak area. There were esters, terpenes, acids, aldehydes, alkanes, heterocyclic compounds and aromatic compounds in the components of body volatiles, and there were 7 common components in body volatiles from female and male O. longicollis, and they were higher in the more relative contents of body volatiles from male O. longicollis.Behavioral responses of O. longicollis to volatiles from banana pseudostems at four physiological status and from female and male O. longicollis were tested with double pitfall olfactometer. The results indicated that O. longicollis showed significantly higher selection rate to volatiles from banana pseudostems at four physiological status and from female and male O. longicollis than clean air. Both female and male O. longicollis selected beetle-eaten and rotten pseudostem not fresh pseudostem. Both female and male O. longicollis showed greater selection to volatiles from male O. longicollis than volatiles from female O. longicollis.Electroantennogram (EAG) responses of O. longicollis to four volatiles were investigated, including (+)-Limonene, Tridecane, Trans-caryophyllene and Alloocimene from banana pseudostems. The results indicated that the four volatiles could all evoke EAG responses of female and male O. longicollis. The EAG responses of female and male O. longicollis to (+)-Limonene(10-4μl/mL) had remarkable difference (P<0.01), to Alloocimene (10-6μl/mL and 1μl/mL) had significant difference (P<0.05). Electroantennogram responses female and male O. longicollis to different concentrations of Tridecane and Trans-caryophyllene and other concentrations of (+)-Limonene and Alloocimene had no sex differences.Antennal sensilla of O. longicollis were observed with scanning electron microscopy. There were wavy grooves on the antenna surface. and the sensilla could be classified into seven types morphologically, including three types of sensilla trichodea, two types of sensilla chaetica, one type of sensilla basiconic and sensilla gemmiformium. There were differences among the distribution and number among the scape, pedicel and flagellum of the antenna.