Developing an ecological basis for managing the threat posed by phosphine resistant stored grain beetles in Australia

22 - 24 September 2009

Phosphine resistant forms of stored grain beetles are a critical biosecurity issue for Australia, and elsewhere.

Knowledge of the ecological processes contributing to the development and spread of resistance is fundamental to managing this problem. Understanding has, however, derived largely from laboratory population studies with relatively little information from the field.

This paper describes the key results obtained from the initial phase of research on the ecology of two major pests, the lesser grain borer (Rhyzopertha dominica) and the rust-red flour beetle (Tribolium castaneum).

A priority is to quantify the dynamic pattern of distribution and abundance of each beetle species across the rural landscape. A long-term trapping program is under way in two grain growing districts, in Queensland and New South Wales. The traps are baited with species-specific pheromones and located near silos, in paddocks and in native vegetation.

The lesser grain borer adults are widely distributed away from grain storages in the two study areas, and are more abundant there than expected from North American results. The rust-red flour beetle is aggregated around grain storage, which is consistent with results from the United States of America.

Other research is in progress to test if individual beetles interact with key aspects of their environment in a species-specific way. For example, attempts are being made to characterise beetles emigrating from infested silos by intercepting individual adults as they leave the storage and evaluating them in the laboratory. Results to date show that R. dominica females have mated before emigrating, that both sexes typically live for three months at 25°C, and that females captured in this way are capable of producing several hundred adult progeny during this time without further mating.

Results such as those described in this talk will provide ecological insights into the evolution and spread of phosphine resistance and therefore contribute to the development of effective resistance management.