Larvicidal efficacy and mode of action of compound composition from Adiantum latifolium on Oryctes rhinoceros

Oryctes rhinoceros Linn., a well known pest of coconut palm, causes irrecoverable damage, reduction in yield and death of the plant. Insecticides with novel mode of action, more target selective and biodegradable are needed to replace the impacts of synthetic pesticides. Unexplored phytochemicals may have unknown site of action, which are selective to insects and, are safe for humans and the environment. Adiantum latifolium is a shade loving fern resistant to pathogens due to the presence of phytocompounds. The study was undertaken to find out the larvicidal efficacy of a compound composition of triterpenoids isolated from the leaves of A. latifolium against O. rhinoceros and its mode of action. The compounds showed antibacterial activity against gut bacteria of the larvae and larvicidal activity (LD50, 19.55 mg/kg), weight loss, 20-hydroxyecdysone titre and precocious metamorphosis of the larvae.. It also induced immunotoxicological effects via cellular and numerical changes of haemocytes in the haemolymph. The synergistic interaction of the triterpenoids is useful in the preparation of improved biopesticides.