Combined effect of microbial and chemical control agents on subterranean termites

Authors: Wright, Maureen; Lax, Alan

Submitted to: Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2013
Publication Date: 10/1/2013
Citation: Wright, M.S., Lax, A.R. 2013. Combined effect of microbial and chemical control agents on subterranean termites. Journal of Microbiology. 51(5):578-583.

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. The identification of novel microbes which cause mortality of Formosan subterranean termites can expand the options available to treat infestations. This work reports the screening of a bacterium for its ability to kill Formosan subterranean termites, and the increased effect it has when combined with a fungus that has been previously shown to kill termites.

Technical Abstract: Subterranean termites are responsible for several billion dollars in damage in the United States annually, including control and repair costs. Formosan subterranean termites (FST) cause a large proportion of this damage. The fungus Paecilomyces fumosoroseus (Pfr) has been previously shown to control FST. The bacterium Bacillus thuringiensis (Bt) is being investigated here for its ability to work synergistically with Pfr. FST were exposed to the specified treatments on dampened filter paper and incubated at ambient temperature and high humidity while mortality was monitored. Controls exposing termites to filter paper wetted with water only were included. Controls and treatments were applied to each of four colonies, with each colony serving as a replicate. Pfr and Bt were applied at doses of 106 and 109, alone and in combination. On day 5, Pfr, Bt, and the combined treatment at the 106 dosage caused 8.75%, 22.5% and 15% mortality, respectively. While the Bt mortality rate is higher than that of the combination, the rates are not significantly different. The control mortality on day 5 was 5%. On day 9 the control mortality rate was 10%. Also on day 9, the combined 106 treatment had killed 35% of the termites, which was significantly higher than the Pfr mortality rate of 12.5%, but not that of the Bt mortality rate which was 27.5%. On day 13 the combined 106 treatment mortality rate was 91.3%, which was significantly higher than all other treatments: control at 17.5%, Pfr at 36.25% and Bt at 35.0%. When Pfr and Bt were applied at the 109 dosage Pfr alone caused a mortality rate of 97.5% as early as day 5. The combination of Bt did not significantly increase the effectiveness of this dosage on any day of the experiment. These data show that combining Pfr and Bt resulted in increased mortality of FST at the 106 dosage, and indicate that investigations of other lower dosages may be beneficial.