Title: Efficacy of aerosol applications of methoprene and synergized pyrethrin against Tribolium castaneum (Herbst) adults and eggs Authors
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 23, 2014
Publication Date: N/A
Interpretive Summary: Aerosol insecticides are being used to control insect pests in flour mills. The red flour beetle is a major pest of flour mills, and the presence of available food material often compromises control. We exposed adults and eggs of the red flour beetle to single applications of pyrethrin aerosol, pyrethrin with the insect growth regulator methoprene, or just to the oil carrier that was in the pyrethrin formulation, all in the presence of a flour food source. Adults were initially incapacitated by pyrethrin aerosol but recovered and were able to reproduce in the flour. Beetle eggs were also exposed to the different treatments in the presence of flour, and as the amount of flour increased adult emergence increased, however, overall emergence was less than in untreated control, which indicated the aerosols had some effect on development. Results show the immature stages of the red flour beetle are more susceptible to pyrethrin aerosol than the adult. Pest managers can use this information to help improve insect pest management programs in flour mills.
Technical Abstract: Experiments were performed to determine the efficacy of a single aerosol application of the insecticides methoprene and piperonyl butoxide-synergized pyrethrin, alone or in combination, and the insecticide carrier, Isopar M, against Tribolium castaneum (Herbst), the red flour beetle. The initial test exposed adults to insecticide treatments and placed male/female pairs in flour. All adults exposed to synergized pyrethrin were knocked down for at least 24 hrs after exposure but they recovered. High adult survival and similar average numbers of living F1 progeny were produced regardless of treatment exposure, which suggests a low efficacy for a single aerosol application against adults. In a separate test, insecticide treatments were directly applied to newly laid eggs which resulted in the suppression of egg hatch. Synergized pyrethrin was the most effective insecticide (P=0.001) for suppressing egg hatch. The effect of flour on insecticide activity to eggs and consequent insect development was also evaluated. An amount of 0.01 g of flour in the exposure arena, 62 cm2 area, was not sufficient for individuals to develop beyond the early larval stages regardless of the treatment. As the flour amount in the arena increased from 1 g to 5 g, the number of eggs that could develop to the adult stage increased but this number was significantly lower in the insecticide treatments than in the control or carrier treatments. The results of the later tests indicate a high efficacy of the insecticides alone or in combination on T. castaneum egg hatch and development to the adult stage.