Study On Behavior Responses Of Bactrocera Dorsalis (Hendel) Ant Its Larval Parasitioids To Their Host Volatiles

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a serious pest insect,attacking more than250species from46families of fruits and vegetables. In presentresearch, the behavior responses of the fly and its parasitoid, Psytallia incise(Silvestri), to their host volatiles were tested with Y-tube olfactometers. Volatiles fromthe tested host plants were analyzed with GC-MS for the component compounds.Afterward, the individual compounds were determined for their elicitedelectroantennogram detection (EAG) responses to antennae of B. dorsalis and its3parasitoid species, i.e. P. incise, Fopius vandenboschi (Fullaway) andDiachasmimorpha longicaudata (Ashmead). At last, the antennal sensilla wereobserved under scanning electronic microscopy (SEM) for P. incise and another twoparasitoid species of the fly, F. vandenboschi (Fullaway) and D. longicaudata(Ashmead).(1) Olfactometer bioassays showed that fruits of all10tested host plant speciesexhibited attraction to both sexes of B. dorsalis adults. The attraction the tested plantsreduces in the order: Musa paradisiacal, Psidium guajava, Chaenomelessinensiskoehne, Averrhoa carambola, Mangifera indica, Amygdalus persica, Dimocarpuslonggana, Fragaria ananassa, Pyrus spp and Citrus sinensis. Fruits attractedsignificantly more B. dorsalis adults than leaves. The attraction of fruits increased asthey ripening. The flies preferred the fly-eaten fruits over the fresh ones which,however, showed higher attraction than the fruits with the fly eggs oviposited in. Tothe same fruits, female adults of the fly presented higher behavior response than themales.(2) Olfactometer bioassays revealed that female and male adults of P. incisechose volatiles of tested fruits of8host plant species. The attraction of fruits to theparasitoids reduced in the order: Musa paradisiaca, Dimocarpus longgana, Psidiumguajava, Chaenomelessinensis Koehne, Averrhoa carambola, Mangifera indica,Citrus sinensis and Amygdalus persica. The preference of P. incise to the flyvolatiles reduced in the order of the fly life stages: lavae, eggs, pupae and adults.The female parasitoids showed stronger orientation to the fly lavae volatilesthan the males. But to the volatiles of eggs, pupae and adults of the oriental fruit fly, both sexes of the parasitoids exhibited similar preference. The attraction ofhost plants to P. incise was affected by the fly feeding, and reduced in the order:fruits eaten by the fly larvae, fresh fruits, fruits with the eggs ovipositted by the fly,and fruits eaten by the fly adults. Mated and unmated adults of the parasitoidsexhibited similar behavior reposes to the same host volatiles.(3) Fruit and leaf volatiles of10host plant species, i.e. Psidium guajava,Fragaria ananassa, Pyrus sp, Mangifera indica, Chaenomelessinensis koehne, Citrussinensis, Averrhoa carambola, Dimocarpus longgana, and Amygdalus persica, wereanalyzed for their component compounds. The volatiles components were dominatedby terpenes with high content and diversity. The volatiles from all tested plant speciescontained a little of alkyl compounds as well as ketones, aldehydes, ethylations,esters and acids. In volatiles of some host plant species, there are a little of benzene,cyanogens, amines and one or several heterocyclic compounds.(4) The oriental fruit fly produced EAG responses to10μg/μL of each(E)-2-decenal, aromadendrene, alpha-farnesene, nerolidol, valencene, ionone,germacrene, dl-Limonene, linalool and caryophyllene. The strongest EAG responsesby adult females and males of the oriental fruit fly were elicited by (E)-2-decenal, andthe lowest EAG response by Caryophyllene. To each of the tested10compounds,EAG response by unmated adult males of the fly was significantly stronger than thatby the mated males. The unmated adult females of the fly were also produced strongerEAG response than the mated females to the tested compounds, except dl-Limoneneand Caryophyllene to which the unmated females produced weaker EAG responsethan the mated. To same compounds, unmated adult males of the fly producedstronger EAG responds than the unmated females. In contrast, the mated femaleadults of the fly presented stronger EAG response than the mated males, except thatthe EAG response to Aromadendrene was stronger by mated males than by matedfemales.(5) The tested parasitoids of the oriental fruit fly, i.e. P. incise, F. vandenboschi,and D. longicaudata, presented EAG responses to all9tested component compoundsof the volatiles of the fly host plants. The responses were different between femaleand male adults of the parasitoids, as well as between the unmated and mated adults.For P. incise, Both of the unmated females and males produced significantly strongerEAG responses to (E)-2-decenal and aromadendrene than to other tested compounds.Mated adults of both sexed presented higher EAG responses to linalool than to other tested compounds. No significant difference of EAG responses was tested betweenthe unmated and mated females when they were exposed to the same testedcompounds, except for the EAG response to linalool. The significant difference ofEAG responses between unmated and mated males of P. incise was only tested withalpha-farnesene and linalool. For F. vandenboschi, both of the mated and unmatedadults presented strongest EAG responses to valencene among the9testedcompounds, and weakest responses to caryophyllene. Mated D. longicaudata femalesproduced the strongest EAG response to alpha-farnesene, and the second strongest to(E)-2-decenal among the tested compounds; the strongest EAG response of the maleswas elicited by (E)-2-decenal, and the second strongest response by aromadendreneand alpha-farnesene.(6) SEM observation of antennal sensilla revealed that P. incis possessed sensillatrichodea, sensilla placodea, sensilla ampullaceous and Bohm bristles with additionalsensilla coeloconica and more sensilla ampullaceous for the males. Parasitoid F.vandenboschi females has5types of antennal senilla, i.e. sensilla trichodea, sensillaplacodea, sensilla ampullaceous, Bohm bristles and sensilla ampullaceous. Male F.vandenboschi adults have the same senilla types as the females except that the maleslack sensilla ampullaceous. D. longicaudata adults of both sexes have4types ofantennal sensilla such as sensilla trichodea, sensilla placodea, sensilla ampullaceousand Bohm bristles.