Distribution and efficacy of pyrethrin aerosol to control Tribolium confusum (Coleoptera: Tenebrionidae) in food storage facilities

A field test was conducted whereby adult Tribolium confusum (du Val), the confused flour beetle, were exposed in Petri dishes lined with filter paper and containing 0-2000 mg of flour, to a pyrethrin-CO₂ aerosol inside an empty warehouse. Applications were made according to label directions, and beetles were exposed to the aerosol for 2 h. After exposure, knockdown was assessed, and beetles were held for 2 weeks either in the same Petri dishes in which they were exposed or transferred with the flour to new Petri dishes lined with clean filter paper. Resident insect populations inside the test warehouse and outside were assessed through the use of pheromone traps. Virtually all beetles were knocked down at the time of removal from the exposure environment. Recovery from knockdown, or survival, increased with the presence of flour, and varied depending on the position of the exposure dishes inside the warehouse. Survival was also greater for beetles transferred along with the exposed flour to new Petri dishes lined with unexposed filter paper, compared to beetles that were held with the flour and the Petri dish that was exposed to the aerosol. Inside the warehouse, Plodia interpunctella (Hübner), the Indian meal moth, and Trogoderma variabile Ballion, the warehouse beetle, were the major species collected in pheromone traps. Large numbers of T. variabile were captured outside the warehouse, but their numbers declined during the study, while captures of P. interpunctella outside remained relatively constant. The intermittent aerosol treatments did not seem to affect these resident populations.