Comparative residual toxicities of carbaryl, deltamethrin and permethrin as structural treatments against three liposcelidid psocid species (Psocoptera: Liposcelididae) infesting stored commodities

Abstract

Residual toxicities of carbaryl, deltamethrin and permethrin were evaluated as surface treatments on concrete (porous surface) and galvanized steel (non-porous surface) panels (0.3×0.3 m2) against adults of Liposcelis bostrychophila Badonnel, Liposcelis entomophila (Enderlein), and Liposcelis paeta Pearman. Residual toxicities of these chemicals were assessed at 30±1°C, 70±2% r.h., and a photoperiod of 12 : 12 h (
), one day after treatment (0 wk) and thereafter at wk 1, 2, 4, 6, 8, and then every 4 wk up to wk 40. Mortality was recorded after exposure periods of 6 h, and then every 24 h until end-point was achieved. Liposcelis bostrychophila was the most susceptible species to the three chemicals tested, followed by L. paeta, and L. entomophila. Deltamethrin on concrete and permethrin on steel were the most successful chemicals, whereas permethrin on concrete and carbaryl on steel were the least successful against all three species. We conclude that for long-term protection, none of the chemicals studied is suitable against any of the three psocid species on concrete storage surfaces. On steel surfaces, only permethrin would deliver long-term protection up to 40 wk against L. bostrychophila and L. paeta infestations. This chemical however, will fail to provide long-term control against infestations where L. entomophila is present.