Master of Science / Department of Entomology / Franklin Arthur / Kun Yan Zhu / Tribolium spp. are major pests in structures used for the processing and storage of grain-based products (e.g., flourmills, warehouses, retail stores). Consumers and regulators have little tolerance for insect-damaged or contaminated food products. The direction and breadth of pest-control strategies in the food industry have changed significantly over the past few years, creating the need to optimize insecticides through improved integrated pest management (IPM) techniques, specifically through the identification of new control agents that are low in mammalian toxicity, as well as any factors that might affect susceptibility to these agents. There is currently renewed interest in developing reduced-risk, low toxicity chemicals that can be effectively utilized in a setting in which grain and other food commodities are vulnerable to insect infestation, as a means of replacing outdated, and at times, less effective methods of insect control. Over the past decade, developed countries have made significant progress toward alternative insect control strategies by employing a variety of applied insecticides. Two classes of insecticide include natural pyrethrum and insect growth regulators (IGRs), which are substances that mimic insect hormones essential to normal development and reproduction. Pyrethrin is a highly efficient, broad spectrum, botanical insecticide that causes a rapid knockdown in exposed insects. Synergists are used to extend the economic usage of natural pyrethrins and because pyrethrum is rapidly metabolized, it is often mixed with a synergist. Methoprene, a juvenile hormone analog, is labeled as an aerosol and surface treatment inside mills, warehouses and other food storage facilities. There is little recent research with large-scale aerosol applications in stored-food facilities; furthermore, there are few published references regarding the efficacy of using methoprene in combination with synergized pyrethrin, in aerosol form. Therefore, the purpose of this research was to evaluate the use of aerosol applications of two aerosol concentrations on flour and finished stored-product packaging materials for the control of Tribolium spp. Results of this research show that T. castaneum are effectively controlled with 1% aerosol application, while the 3% formulation is required to effectively control T. confusum. With regards to the various packaging material surfaces, few differences between the surfaces emerged.

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.