Interaction of the predatory ant Pheidole megacephala (Hymenoptera: Formicidae) with the polyphagus pest Xylosandrus compactus (Coleoptera: Curculionidea)

Abstract

We evaluated the potential of using Pheidole megacephala as a biological control agent against the coffee twig borer Xylosandrus compactus (Eichhoff), an economically important pest of Robusta coffee in Uganda. Upon observing that P. megacephala was common in coffee fields infested by X. compactus, we tested hypotheses that (1) P. megacephala feeds on all stages of X. compactus, (2) P. megacephala can enter galleries of X. compactus inside coffee twigs in search for the prey and (3) P. megacephala’s presence on infested twigs reduces populations of X. compactus in the galleries. In a Petri dish bioassay over 24h, we found that P. megacephala preyed upon all stages of X. compactus without indication of preference. We caged up X. compactus infested twigs with P. megacephala in a plastic container over 48h and found that the predator was unable to enter the galleries. Lastly, we caged up intact X. compactus infested coffee twigs in the field with muslin cloth sleeves for one month and found that P. megacephala reduced the population of X. compactus per twig by almost 22-fold compared to the untreated control. We concluded that P. megacephala is an indiscriminate predator of all X. compactus stages, and, though unable to enter X. compactus galleries, the predator may reduce X. compactus population on infested twigs. Exploitation of P. megacephala in the biological control of X. compactus on coffee and other crops would require additional studies on how to enhance presence of the predator on the infested crop.