Ovicidal potential of plant extract mixtures against the Asian spongy moth (Lymantria dispar asiatica)

The Asian spongy moth (ASM, Lymantria dispar asiatica) is a destructive pest of forests, agricultural fields, and urban areas. Plant extract mixtures were evaluated as alternative tools for integrated pest management targeting the overwintering eggs of ASM. When formulated with an adjuvant able to penetrate the hairy egg mass, plant extract mixtures inhibited egg hatching. The extract mixture (cinnamon extract 5% + citronella oil 10% + citrus oil 30% + derris extract 10% + neem extract 20% + penetrating surfactant 25%) with the highest ovicidal activity (97.6% mortality) is a potential botanical insecticide for use against ASM eggs. Susceptibility to mortality from plant extract mixtures increased with egg maturation. Optimal timing for control of overwintering ASM eggs corresponded to the period in spring when larvae inside eggs were fully differentiated. These results will help improve control efficacy with a day-degree model that predicts egg hatch as well as future development nano-formulations.