Mortality and repellent effects of microbial pathogens on Coptotermes formosanus (Isoptera:Rhinotermitidae)

Authors: Wright, Maureen; Cornelius, Mary

Submitted to: BMC Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2012
Publication Date: 12/15/2012
Citation: Wright, M.S., Cornelius, M.L. 2012. Mortality and repellent effects of microbial pathogens on Coptotermes formosanus (Isoptera:Rhinotermitidae). BMC Microbiology. 12:291 (7 pages).

Interpretive Summary: Subterranean termites cause several billion dollars in damage and prevention costs in the United States annually. The Formosan subterranean termite is responsible for a large and growing proportion of the cost. Novel chemicals which are non-repellant and slow-acting have been developed to control termite activity. Repellency can limit the potential of microbes as new termite control agents. This work reports the screening of two fungi and one bacterium for both their ability to kill Formosan subterranean termites and for the likelihood that they will repel termites in different materials.

Technical Abstract: Two entomopathogenic fungi and one bacterium were tested for their ability to cause mortality of Formosan subterranean termites (FST) after exposure in liquid, and for their propensity to repel FST. The fungus Paecilomyces fumosoroseus (Isaria fumosorosea) strain 3581 at 109 spores/ml caused 82.5% mortality on day 7 which was significantly higher than the control and 106 treatment. On day 14, the 106 and 109 concentrations caused 38.8% and 90.0% mortality, respectively, both being significantly higher than the control. On day 21, 82.5% of the termites were killed by the 106 spores/ml treatment and 91.3% were killed by the 109 spores/ml treatment. At neither the 106 spores/g nor 108 spores/g concentration did P. fumosoroseus repel termites in the tested substrates: sand, soil and sawdust. The fungus Metarhizium anisopliae strain 30905 at 108 spores/ml caused 57.5% mortality on day 7, 77.5% mortality on day 14 and 100% mortality on day 21. On all three days the rate of mortality was significantly higher than that of the control and 106 spores/ml treatment. M. anisopliae also did not cause repellency of FST in sand, soil or sawdust. The bacterium Bacillus thuringiensis strain 33679 did not cause significantly higher mortality than the control on days 7, 14 or 21. Also, of the microbes tested this was the only one to exhibit repellency, and only in one substrate. When termites were exposed to cells only of B. thuringiensis in sawdust a significantly higher number remained in the control tubes after 24 h exposure. The repellent effect was not seen with B. thuringiensis spores only, or a mixture of spores and cells, nor with cells only in the other substrates.