Residual efficacy of contact insecticides on wood and metal surfaces against stored product insects held in shipping containers in Arkansas

Stored product insects pose a significant threat to global trade by infesting packaged commodities in containers during shipment, yet current pest management strategies beyond fumigation remain limited. Contact insecticides offer a promising alternative for suppressing infestations in shipping environments between fumigations. This study evaluated the initial and residual efficacy of two contact insecticides, Tempo® SC Ultra (β-cyfluthrin active ingredient (a.i.)) and Gravista™ (deltamethrin+ methoprene+ piperonyl butoxide (a.i.)), applied to wood and metal surfaces stored inside shipping containers during summer (May – September) and winter (October – February) in Arkansas. A total of 300 bioassay arenas (150 per treatment) were constructed using plywood and steel affixed to the bottom of a 529 cm2 Petri dishes and were treated using a handheld sprayer. Five arenas per surface and treatment combination were randomly selected every 4 wks up to 16 wks of storage Ten adults of either species, along with food, were introduced into each arena, and observed for live, affected, or dead adults every 1, 2, and 7 d of continual exposure. Preliminary results shown that mortality was higher on the combination insecticide (>90%) compared to the β-cyfluthrin insecticide (>85%) across all weeks and surfaces. Mortality was higher on metal than on wood for both insect species, however mortality declined over the 16 wk period for both surfaces. This study provides valuable insight into the potential use of residual insecticide as a pre-container treatment for managing insect infestations in shipping containers during global transit.