Application of biological control agents in mound building termites (Isoptera: Termitidae) -: Experiences with Metarhizium in Australia

The ubiquitous entomopathogenic fungus, Metarhizium anisopliae, is well know to be effective in killing termites under laboratory conditions. Since the infectious conidia are easily mass produced, store well and can be formulated as mycoinsecticides, there is considerable interest in using this fungus for termite control. Studies in Australia have shown that the fungus is not a significant natural mortality factor in termite colonies but that isolates from termite associated material are often the most virulent. One such isolate, FI-610, has been selected for detailed evaluation. Initial studies showed that behavioral factors were responsible for limiting epizootic spread within a termite colony. However field trials have shown that, when sufficient conidia are well distributed in the central nursery area of the nest, conidial treatments are effective in killing colonies of mound. building termites such as Coptotermes lacteus and Nasutitermes exitiosus; Initial tests with FI-610 in bait-boxes and in baits showed repellency to be a major limitation. Two approaches have been followed to overcome this problem. In the first approach, less repellent but still virulent isolates have been sought, while in the second approach various formulations have been tested to overcome this repellency. Fl-1186 is an isolate which demonstrates reduced repellency but retains reasonable virulence. However in field tests, this isolate has proved ineffective. A dilute nonrepellent formulation of FI-610, however, has given much more promising results. Recent small-scale field trials have shown that mound nests of N. exitiosus can be killed by baiting with this new formulation of FI-610. Further studies are needed under more realistic conditions to confirm the potential of this strategy.