Trunk Injection of Systemic Insecticides to Control Stem and Leaf Gall Wasps, Josephiella Species (Hymenoptera: Agaonidae), on Chinese Banyan (Rosales: Moraceae) in Hawaii

Abstract

Chinese banyan, Ficus microcarpa L. f. (Rosales: Moraceae), is a popular landscape tree in many tropical regions of the world. In Hawaii, these trees are severely infested by 2 host-specific insect species in the family Agaonidae (Hymenoptera: Chalcidoidea): the Chinese banyan leaf gall wasp, Josephiella microcarpae Beardsley & Rasplus, and the stem gall wasp Josephiella sp. (currently being described). Infestations by these insects result in gall formation on young leaves and shoots, premature leaf drop, new shoot death, poor tree health, and eventually death of the tree. We evaluated the efficacy and persistence of 2 systemic insecticides, imidacloprid and emamectin benzoate, with or without phosphorous acid amendment, delivered through trunk injection to control these 2 wasp species in Honolulu, Hawaii. Although both systemic insecticides had some effect against leaf gall wasps for up to 18 mo post treatment, only emamectin benzoate persisted against stem gall wasps for up to 14 mo post treatment. Phosphorous acid amendment did not provide any benefits for Chinese banyans to mitigate wasp infestations. In conclusion, trunk injection of emamectin benzoate could be a feasible management strategy to control stem and leaf gall wasps on Chinese banyans in Hawaii.