Effect of methoprene impregnated polymer packaging on development of Tribolium castaneum and Trogoderma variabile

Methoprene is an insect growth regulator registered as a grain protectant and also as an aerosol or residual surface treatment inside structures. It is currently being evaluated as a packaging treatment.  The objective of this study was to evaluate normal adult emergence of Tribolium castaneum (Herbst) and Trogoderma variabile Ballion from eggs laid by adult beetles on the inside and outside surfaces of methoprene-treated packaging material at 27 and 32°C and 60% RH.  Inside and outside surfaces of methoprene-treated and untreated packages were cut into discs and fitted into 62 cm² Petri plates, and 500 mg of flour (T. castaneum) or vanilla shake mix (T. variabile) were added to the plates.  Ten mixed sex adults of a particular species were added to an individual plate. Adult T. castaneum were removed after 7 days and T. variabile were removed after 3 days.  Both the inside and outside surface of  the treated packages resulted in 100% supression of normal T. castaneum adults.  T. castaneum progeny were arrested in the larval stage or developed as far as pupal-adult intermediates at both temperatures on both the outside and inside surface.  T. variabile progeny developed to the pupal-adult stage at both temperatures on the outside surface, while on the inside surface surface progeny were able to complete development as F1 adults and at 27°C there was no difference in the number of progeny adults between the treatment and untreated controls.  However, at 32°C there was a reduction in progeny adults compared to untreated controls.