Efficacy of Phosphine on Different Life Stages of Alphitobius diaperinus and Tenebrio molitor (Coleoptera: Tenebrionidae)

The efficacy of phosphine has been established for numerous major stored product insects. However, data related to the evaluation of the effect of phosphine on Tenebrio molitor L and Alphitobius diaperinus Panzer are limited. The present study aims to evaluate the susceptibility of these species to phosphine by using the following evaluation protocols: (a) all life stages were exposed for 3 days to different concentrations of phosphine, (b) adults were exposed to 3000 ppm until all exposed individuals were immobilized, using the Phosphine Tolerance Test (PTT, Detia Degesch GmbH, Germany), and (c) adults were exposed to 3000 ppm of phosphine for 90 min by again using the PTT protocol. For all series of bioassays, delayed mortality was recorded 7 and 14 d post-exposure. According to our results, 100 ppm for three days was sufficient to kill all life stages, including the eggs, for both species. Alphitobius diaperinus adults were found to be more tolerant than those T. molitor, as noticeable survival was observed, even after 90 min of exposure to 3000 ppm. Our study provides some initial data for the efficacy of short and long exposures of A. diaperinus and T. molitor to phosphine.