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Doctor of Philosophy / Department of Entomology / James F. Campbell / Kun Yan Zhu / Aerosol applications of reduced risk insecticides such as synergized pyrethrin and insect growth regulators (IGR) are part of food industry integrated pest management programs. Since aerosols cannot penetrate into hidden areas exploited by pests such as the red flour beetle, Tribolium castaneum, the potential for these insecticides to effect beetle populations was evaluated. Because IGRs do not cause immediate mortality, the potential of horizontal transfer for an IGR from treated to untreated individuals was also examined. Results showed that when untreated T. castaneum, larvae or pupae, were added to flour containing methoprene, IGR, treated larvae, pupae or adults, the untreated individuals exhibited evidence of methoprene exposure (external deformities and reduced survival). Evaluation of the different mechanisms of transfer indicated that contact with methoprene treated individuals or flour that had been in contact with treated individuals may be the primary method of methoprene transfer. Since aerosols are often applied as a combination of IGR and pyrethrin with a carrier, the effect of these components was evaluated. Applications of synergized pyrethrin caused knockdown of adults but affected adults recovered and progeny production was not effected. Exposure of eggs to these insecticides reduced egg hatch. Food material accumulations inside food facilities can potentially increase or reduce insecticide efficacy. Evaluation of different flour residue levels, representing different sanitation levels, revealed that sanitation alone reduced immature development. As flour residue depths increased more individuals developed into adults but very few developed in the insecticide treatments. Food facilities that use aerosol insecticides apply them at regular intervals, so the cumulative effects of these treatments were considered. Experiments evaluating repeated insecticide exposures indicated that the direct morality from synergized pyrethrin not the horizontal transfer of methoprene was the primary factor in population reduction. Overall findings suggested that methoprene is highly mobile between different surfaces. Exposure of untreated individual beetle larvae to treated larvae or pupae or to flour that has been in contact with exposed beetles can have detrimental effects on development or survival, but these effects may be highly variable and even in cumulative exposures the overall level of population suppression is limited.

Master of Science / Department of Entomology / Frank H. Arthur / Kun Yan Zhu / Experiments were conducted to assess the effects of direct and indirect exposure scenarios, different degrees of residual flour, open and obstructed positions, and seasonal temperature variations on the efficacy of synergized pyrethrin against the red flour beetle, Tribolium castaneum (Herbst) and the confused flour beetle, Tribolium confusum Jacquelin du Val. To evaluate effects of direct and indirect exposures of T. castaneum and T. confusum eggs, larvae, pupae, or eggs to the insecticide aerosol within a flour mill, the following treatments were made to each life stage: insects treated with aerosol and transferred to treated or untreated flour, untreated insects transferred to treated flour, and insects and flour combined and treated together. Different degrees of harborage or sanitation levels were created by exposing T. confusum larvae, pupae, and adults to pyrethrin aerosol in Petri dishes containing 0, 0.1, 1, 5, and 10 g of wheat flour. Effects of pyrethrin dispersal in open and obstructed positions and seasonal temperature variations were assessed by exposing T. confusum pupae and adults in open positions and inside wooden boxes (1 m long, 20 cm wide, and 5, 10, or 20 cm high) inside experimental sheds maintained at target temperatures of 22, 27, and 32 °C. Results showed that when T. castaneum and T. confusum were directly exposed to aerosol without the flour source, or with a low amount of flour at open exposed areas, the aerosol provided good control against all life stages of T. castaneum and T. confusum. However, when insects were indirectly exposed (treated together with flour or untreated insects were transferred to treated flour), or treated together with deeper flour amounts, and exposed inside the boxes, the efficacy was greatly reduced. Eggs and pupae of both the species were more susceptible compared to larvae and adults. Additionally, the moribund adults initially observed in indirect exposure treatments, or at the deeper flour depth and exposure positions insides the boxes, were better able to recover. Generally, temperatures in the range of 22-32 °C had no significant effects on overall efficacy of pyrethrin aerosol.