Apparent synergy among defense mechanisms in subterranean termites (Rhinotermitidae) against epizootic events: limits and potential for biological control.

The use of entomopathogens for biological control of subterranean termites (Rhinotermitidae) has attracted attention in the past four decades, and several laboratory studies have shown promising results with fungal agents. This approach was based on the concept of classical biological control with the use of a virulent agent that can self-replicate in a termite nest and be transmitted among individuals, resulting in an epizootic to kill the entire colony. However, the absence of positive results in field studies challenged the potential of fungal pathogens as a realistic approach for subterranean termite control, and the relationship between fungi and subterranean termites remains poorly understood. A multimodal approach of the currently identified defense mechanisms allowed us to show that subterranean termites have the ability to prevent an epizootic from occurring. The defense mechanisms involved in such resistance are reviewed and documented. Finally, the interactions among three major defense mechanisms (grooming, cellular encapsulation, and gut antifungal activity) were analyzed, and it is suggested that these mechanisms act synergistically to produce an efficient defense against the infection of the fungus at the individual and group level so as to protect the colony from epizootics.