Growth regulator insecticides for the control of the lesser mealworm beetle Alphitobius diaperinus (Coleoptera: Tenebrionidae)

The purpose of this study was to evaluate the efficiency of the insecticides methoxyphenozide, teflubenzuron, pyriproxyfen, chlorantraniliprole and also Azadirachta indica in the control of Alphitobius diaperinus (Coleoptera: Tenebrionidae). The study was carried out in the Microbial Control laboratory of Universidade Estadual Londrina (Brazil) and consisted of two bioassays. In the first, A. diaperinus larvae were fed with corn feed treated with the insecticides in seven dosages. In the second bioassay, the different treatments were sprayed on the larvae only at the three highest dosages. Evaluations were performed daily, quantifying larval mortality, and on the 30th day, the number of pupae and adults were evaluated. Teflubenzuron, chlorantraniliprole and A. indica were responsible for the greatest percentage of mortalities in larvae fed with treated feed. The treatments with methoxyphenozide and pyriproxyfen caused the lowest mortalities; however, with pyriproxyfen the larvae were not transformed into pupae and adults up to the 30th day of assessment. The treatment with teflubenzuron showed the greatest toxicity, with the lowest survival time (ST50) When the products were applied directly on to the larvae, the most efficient treatments were teflubenzuron, chlorantraniliprole and A. indica; however, there was a reduction in the mortality percentages with teflubenzuron and chlorantraniliprole in relation to the feed bioassay. For A. indica, the application method did not affect the mortality levels. Pyriproxyfen, which had not led to mortality through feed ingestion, obtained an increase of up to 30% after being applied directly on to the larvae.