Resistance management and the ecology of <i>Rhyzopertha dominica</i> (F.) and <i>Tribolium castaneum</i> (Herbst) in subtropical Australia

Abstract

Subtropical Australia is a demonstrated hotspot for phosphine resistance in stored product pests. Rhyzopertha dominica and Tribolium castaneum are common pests of stored grain in this region and management of these pests is increasingly impeded through the spread of resistance to phosphine, the most desirable control method. A number of field-oriented studies were conducted from the 1970’s to 1990’s to understand the ecology of these pests in subtropical Australia, including seasonal abundance, flight and population growth in stored grain. To manage the evolution and spread of resistance we require an understanding of movement of these beetles among foci of infestation. This paper presents preliminary analyses of two aspects of new research on these species: (1) a trapping program using pheromones to investigate beetle numbers in spatial and temporal contexts, and (2) characterisation of beetles leaving infested farm silos. Adults of both species were trapped throughout the year with the lowest numbers corresponding to the coldest part of the year. The coldest trapping period had mean maximum and minimum temperatures of 21.1 and 3.5°C respectively. Trapping also revealed distinct differences between the two species, both in terms of numbers caught and where they were caught. In general, more R. dominica were caught than T. castaneum, similar numbers of R. dominica were caught near farm silos and in paddocks at least 1 km from the nearest silo, and more T. castaneum were caught near silos than in paddocks. Individual adults intercepted flying from farm silos are being characterised in the laboratory, and results to date show that these adults are long-lived, the females have mated before emigrating and are highly fecund. By undertaking research of the type summarised here we aim to develop an understanding of how these two species interact with their environment and how these interactions influence resistance development.

Keywords: Ecology, Rhyzopertha dominica, Tribolium castaneum, Australia