Laboratory Evaluation of Boric Acid and Azadirachtin in combating Rhynchophorus ferrugineus (Coleoptera: Curculionidae: Dryophthorinae)

Background: the red palm weevil, Rhynchophorus ferrugineus (F.) (Col.: Curculionidae: Dryophthorinae) is a pest species that infests many palm and coconut tree species across 50 countries. Larval feeding damages the palm heart and/or the palm stipe meristem, often causing the tree’s death. The damage caused by the larvae also allows phytopathogens and other insect pests to enter the tree, which can prove lethal. Methods: two active ingredients, azadirachtin and boric acid, were incorporated into an artificial diet fed to the weevils. The efficacy of these compounds was evaluated through bioassays conducted under laboratory conditions. Results: the most effective concentration for azadirachtin (95.0±5.0 %) was observed at 50.0 ppm on day 20; for boric acid (100 %), it was most efficacious at 2,500.0 ppm on day 12. Conclusions: boric acid shows significant potential in controlling the larvae of this weevil pest species. It does so in two ways - firstly, through its direct action against the red palm weevil larvae, and secondly, by its interaction with the micro-organisms associated with the larvae, which may result in more rapid mortality amongst the pest larvae themselves.