Spatial Distribution and Flight Patterns of Two Grain Storage Insect Pests, Rhyzopertha dominica (Bostrichidae) and Tribolium castaneum (Tenebrionidae): Implications for Pest Management

SIMPLE SUMMARY: Lesser grain borer (LGB) and rust red flour beetle (RFB) are two common insect pests that cause severe economic damage to stored grain worldwide. Current treatments rely on chemicals, but both species have developed resistance to most of these. However, by understanding the ecology of these species in regional locations it is possible to develop more targeted pest management strategies. Therefore, we conducted a 2-year trapping study to investigate for the first time the spatial and temporal activity of these two species in a temperate region of southeastern Australia. Traps were located both on and off farms. Of the two species LGB were more common, and higher numbers of both species were found in traps close to grain storages. However, they both had a wide distribution as they were caught in all traps. Both species displayed distinct seasonal trends, with activity stopping over the colder, winter months in both years. The lack of activity is partly a response to the colder temperatures, with flight activity stopping below 14.5 °C for LGB and 15.6 °C for RFB. These results can be used to inform pest management activities such as cleaning of storages, monitoring for insects, resistance management, and site hygiene. ABSTRACT: The lesser grain borer, Rhyzopertha dominica, and the rust red flour beetle, Tribolium castaneum, are two major beetle pests commonly found infesting stored products worldwide. Both species can cause severe economic damage and their management is complicated by their potential to develop resistance to several of the limited chemical options available. However, pest management strategies can be improved by understanding the ecology of the pest insect. To determine the spatiotemporal activity of R. dominica and T. castaneum, we conducted a trapping study over two years in a temperate region of south-eastern Australia, with traps located near grain storages and fields. We captured higher numbers of R. dominica than T. castaneum, and both species were more prevalent in traps located close to grain storages. Similar and consistent seasonal patterns were displayed by both species with activity ceasing during the winter (June–August) months. We found linear correlations between maximum daily temperatures and trap catches, and minimum threshold temperatures for flight activity were 14.5 °C and 15.6 °C for R. dominica and T. castaneum, respectively. The results are discussed in relation to the ecology of these pests along with their implications for pest management.