Testing a co-formulation of CO2-releasing material with an entomopathogenic fungus for the management of subterranean termite pests

Abstract

Termites cause significant damage to cocoa trees. Entomopathogenic fungi (EPFs) such as Metarhizium brunneum have been considered as a sustainable alternative to abusive use of insecticides against termites. However, potent EPF application is limited by its repellency effects, host avoidance, and termite defense mechanisms such as grooming among nest mates. Termites use CO2 to locate plant roots. This study investigated whether CO2-emitting capsules could attract termites. Capsules formulated without fungus (CEC) as well as those formulated with M. brunneum Cb15-III (CECEPF) were tested for attractiveness to termites with other attractive components using modified four-arm olfactometers. Worker termites’ infection by the fungus growing from the capsules as well as its horizontal transmission was assessed through the autodissemination approach. Significantly, more termites were attracted to CEC compared with other attractive components. Higher number of termites was attracted by CECEPF and cocoa seedlings than dry wood and yeast in a choice test. When termites were directly exposed to sporulating capsules, 100% mortality was obtained within 5 days. However, in the horizontal transmission experiment, no significant differences were observed as regards termites’ mortality in the treatment compared with the control groups. CECEPF did not cause any apparent repellency to termites as compared with CEC. This strategy offers high potential to promote biological termite control using CECEPF as alternative to insecticides. Further studies are warranted to evaluate the efficacy of these capsules under field conditions and explore their commercialization for termite management.