Insecticidal effect of deltamethrin, pyrethrin, and spinosad on metal and concrete surfaces on six species of stored product insects

Contact insecticides are one of the most used control and prevention methods for managing stored product insects however, the efficacy of organic or natural insecticides across multiple surfaces is limited. The objective of this study was to evaluate a deltamethrin, pyrethrin, and spinosad insecticide formulations applied to metal and concrete surfaces to control adults of six species of stored product insects. Metal and concrete arenas were treated with an insecticide, and ten adults of each species, including Tribolium castaneum (Herbst), Rhyzopertha dominica (F.), Cryptolestes ferrugineus (Stephens), Tribolium confusum Jacquelin du Val, Sitophilus zeamais Motschulsky, or Oryzaephilus surinamensis (L.), were added to treated arenas and evaluated for survival at 1, 3, or 7 days after exposure. Insect survival was significantly lower on metal (nonabsorbent) compared to concrete surfaces (absorbent). Among all species, insect survival was <5 % on metal surfaces treated at the high label rate of pyrethrin. Tribolium castaneum and T. confusum were the two most tolerant species. Tribolium spp. survival ranged from 40 to 100 % on metal and concrete arenas treated with deltamethrin and spinosad. Overall, all the insecticides were more effective on metal surfaces. Results of this study demonstrate the broad-spectrum efficacy of three different formulations of contact insecticides, however their efficacy depends on the surface substrate. Thus it is imperative that the species and surface properties be considered before application of a contact insecticide to provide a more targeted application treatment in processing facilities, storage areas, or as a pre-bin treatment. • Longer exposure times on treated surfaces greatly reduced insect survival. • Tribolium spp. were the most tolerant species to all insecticide formulations. • Insect survival was lower on metal compared to concrete.