Submitted to: Journal of Economic Entomology Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 10, 2005
Publication Date: October 1, 2005
Citation: Wright, M.S., A.K. Raina and A.R. Lax. 2005. A strain of the fungus Metarhizium anisopliae for controlling subterranean termites. Journal of Economic Entomology. 98(5):1451-1458. Interpretive Summary: Subterranean termites cause an estimated $1 billion 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 in an effort to control termite activity. This work reports the development of fungal termite enemies as biological control agents that will complement the chemicals in an Integrated Pest Management scheme. This manuscript reports the isolation of a new strain of the fungus Metarhizium anisopliae that causes rapid and significant mortality to termites. Termites exposed to the new strain died faster than those exposed to a strain of M. anisopliae that was previously sold commercially to control termites. These results can lead to the development of a formulation of this strain for treatment of trees and other infested areas to suppress termite colony activity.
Technical Abstract: Alates of the Formosan subterranean termite (FST), Coptotermes formosanus (Shiraki), collected after swarming in 2002 died within 48 hrs, and the cadavers were visibly infected with a fungus. Fungi were picked from the cadavers, transferred to media and ultimately isolated to purity. The individual fungal cultures were then used to infect FST workers. A single fungal isolate, C4-B, taxonomically identified as Metarhizium anisopliae (Metschnikoff), was found to cause rapid mortality of FST alates. This is the first report of a biological control agent for termite alates. In initial experiments, C4-B was more lethal to both alates and workers when compared to M. anisopliae strain ESC 1, previously marketed as the termite biocontrol agent BioBlast'. Dose response assays in which FST alates were exposed to a known concentration of C4-B spores revealed that 106 spores/ÿl killed 100% of the alates in 3 days, both 105 and 104 spores/ÿl in 6 days, 103 spores/ÿl in 9 days, and 100 spores/ÿl in 12 days. Assays with workers demonstrated that 106 and 105 spores/ÿl killed 100% of the workers in 6 days. In an experiment to test the transfer of inoculum from infected workers to uninfected nestmates, 62.8% of the workers died in 21 days when only 20% of the workers had been inoculated. Mortality of alates caused by C4-B was tested at two field sites by dispersing fungal spores on grassy lawns and collecting alates from the treated areas. Alates thus infected showed 100% mortality by day 5, while only 64.8% untreated control alates from the same collection area were dead on that day.