Plodia interpunctella and Trogoderma variabile larval penetration and invasion of untreated and methoprene-treated foil packaging

Packaged food products inside retail stores and food warehouses are susceptible to infestation by stored-product insects. The insect growth regulator methoprene can be impregnated onto packaging materials to help limit stored-product insect population development and prevent infestations. The objectives of this study were to determine the effect of methoprene-treated foil packaging on egg hatchability and the penetration and invasion ability of the warehouse beetle, Trogoderma variabile Ballion, and the Indian meal moth Plodia interpunctella (Hübner). Twenty-five eggs of each species were added to Petri dishes containing untreated packaging or packaging containing 0.1, 0.25, and 0.5% of the active ingredient methoprene. Petri dishes were held for 7 d in an environmental chamber at 27 °C and 60% r.h. to determine percent hatchability of eggs. Additionally, 6 cm by 8 cm food packages were created from untreated and methoprene-treated packaging and placed into 0.18-L vials. First or third instars of each species were introduced into vials containing diet or no diet, to determine penetration ability after 21 and 42 d. In a separate experiment, packages were pierced with pinholes, and first instar T. variable or P. interpunctella were introduced and observed after 21 and 42 d for package invasion. The foil packaging had no significant effect on egg hatchability of either species. T. variabile were unable to penetrate or invade any foil packages. P. interpunctella invaded all packages containing pinholes. The methoprene-treated packaging reduced adult emergence of P. interpunctella and caused pupal and adult deformations in T. variabile. Methoprene-treated packaging presents a valuable option for food manufacturers to prevent insect infestations and maintain integrity of packaged food products.