INFLUENCE OF PERMETHRIN DROPLETS ON MOVEMENT OF LARVAL PLUTELLA-XYLOSTELLA (LEPIDOPTERA, PLUTELLIDAE)

The behavioral response of larvae of the diamondback moth (Plutella xy lostella L.) to permethrin droplets was investigated through computer simulations and videotape analysis of larval movement on treated surfa ces. Simulations of pre-contact avoidance responses and post-contact h ypersensitivity responses indicated that the different response types would produce different effects on larval speeds and leaving times in the presence of insecticide. Analysis of actual larval movement in tre ated arenas demonstrated that responses to permethrin consistent with the predictions for pre-contact avoidance did occur. Larval speeds wer e higher in trials with insecticide droplets than in controls, and the se differences arose prior to contact with droplets. When a higher ins ecticide concentration was used for droplets, the response observed wa s consistent with a relatively longer distance avoidance response than when droplets had lower permethrin concentrations. Such a response to permethrin should significantly decrease larval exposure to insectici des and increase survival in permethrin-treated fields.