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Title: Behavioral and electrophysiological responses of Coptotermes formosanus Shiraki towards entomopathogenic fungal volatiles

item HUSSAIN, ABID - South China Agricultural University
item TIAN, MING-YI - South China Agricultural University
item HE, YU-RONG - South China Agricultural University
item Bland, John
item GU, WEN-XIANG - South China Agricultural University

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2010
Publication Date: 9/29/2010
Citation: Hussain, A., Tian, M., He, Y., Bland, J.M., Gu, W. 2010. Behavioral and electrophysiological responses of Coptotermes formosanus Shiraki towards entomopathogenic fungal volatiles. Biological Control 55:166–173.

Interpretive Summary: Termite behavior towards fungi depends on the type of volatile chemicals released by the fungi. This study showed how the Formosan subterranean termite reacted towards three species of fungi. When forced to come into contact with the fungi, one species quickly killed the termites, while the second species took twice as long, and the third species took four times as long. When the termites were exposed to fungi but not forced to contact the fungi, the species that had killed the fastest caused the termites to be repelled from the fungi the most, and killed them the least. Likewise, the species that had killed termites the slowest showed no repellency and killed them the most. It was also discovered that termite antennae could detect the fast killing, repellent fungal species better than the other two species. The volatile chemicals that were produced by the fungi were identified, showing differences between the species.

Technical Abstract: Termites adjust their response to entomopathogenic fungi according to the profile of the fungal volatile organic compounds (VOCs). This study first demonstrated the pathogenicity of Metarhizium anisopliae, Beauveria bassiana and Isaria fumosorosea (=Paecilomyces fumosoroseus) towards the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Using no choice assays, M. anisopliae was found to be highly virulent (LT50 3.10 d) as compared to B. bassiana (LT50 6.62 d) and I. fumosorosea (LT50 12.39 d). Secondly, using choice assays, the foraging behavior of C. formosanus was determined in the presence of pathogenic fungi. C. formosanus workers in close contact with highly pathogenic fungi (M. anisopliae) elicited a repellent response causing most of the termites to forage in a safe zone, furthest from the fungal source. This repellency resulted in relatively low mortality similar to controls. The repellency of M. anisopliae conidia can be used to protect human belongings and timber from termites. While I. fumosorosea cultures did not show any repellency to C. formosanus workers, the termites were successfully controlled with high mortality. Electroantennographic responses of workers showed approximately 47% and 78% reduction in response to the spores of B. bassiana and I. fumosorosea as compared to M. anisopliae, respectively. The VOC profile of repellent cultures of M. anisopliae mainly consisted of paraffins (60.97%), while the major proportion of the I. fumosorosea profile consisted of branched and cyclic alkanes (84.41%). From above findings, it is concluded that the incorporation of I. fumosorosea may increase the biocontrol potential of bait.