Research in Biological Control of the Formosan Subterranean Termite

Abstract

The Formosan subterranean termite, Coptotermes formosanus Shiraki, is a worldwide distributed pest of wooden structures and living plants that causes huge economic losses. Compared to chemical pesticides, biological control may provide a more environmentally friendly and persistent method for the control of C. formosanus. In this research, a series of studies were conducted to understand the termite-pathogen interaction and to develop a feasible biological control strategy. In the first part of the research, the toxicity of Bt toxins expressed by genetically modified maize to termites was tested. Plant tissues or extracts of three commercially planted Bt maize and two non-Bt maize were provided to termites as food. The results revealed no significant difference in survival rate, food consumption or length of tunnels among termites feeding on Bt and non-Bt maize. The following experiments show that maize cob can be used as a termite bait matrix. In the second part of the research, the susceptibility of C. formosanus to MosquitoDunks®, which contains about 10% of the entomopathogenic bacterium, Bacillus thuringiensis subspecies israelensis, was tested. No-choice and choice bioassays did not show a promising lethal effect of MosquitoDunks® on termites. Furthermore it was shown that C. formosanus can suppress the growth of B. thuringiensis. Also, clay was tested for its potential to be a termite bait matrix that can be used to encapsulate biological control agents. Choice tests showed that significantly more termites aggregated in chambers where clay was provided, indicating the possibility of clay to be used as a termite attractant. In the third part of the research, the potential to combine a biological control agent and a chemical pesticide against termites was investigated. The effect of low concentrations of lufenuron, a chitin synthesis inhibitor, on termite physiology and behavior was tested. Results showed that lufenuron significantly reduced vigor and disease resistance of termites. In the following experiments, termite mortality was significantly higher and synergistic in the combination of lufenuron and Pseudomonas aeruginosa (Schroeter) compared to treatment of lufenuron or P. aeruginosa alone. To combine lufenuron and a termite pathogen may bring a successful IPM strategy for the control of termites.