A Comprehensive Assessment of the Impacts of the Insect Growth Regulator Methoprene on Soil Mites and Function in Brisbane, Australia.

Abstract

The incursion of the globally notorious pest, red imported fire ant Solenopsis invicta (Buren) (Hymenoptera: Formicidae: Myrmicinae) in Brisbane, Australia necessitated the prompt design and implementation of an integrated pest eradication solution. The solution included the broad-scale application of the insect growth regulators Methoprene and Pyriproxyfen. Known for high efficacy and low toxicity to selected non-target taxa in the laboratory, these chemicals have received scant attention to identify real non-target species impacts in the field. It was the purpose of this study to provide a real-time assessment of the impacts of Methoprene on the soil ecosystem, examining both its chemical and biological composition. This was achieved by constructing a Before-After, Control-Impact (BACI) experiment, where Methoprene was applied to ‘treated’ (i.e. impact) sites following Fire Ant Control Centre (FACC) protocols. A series of soil samples were collected over repeated Methoprene applications, and analysed to determine mite diversity, community structure and chemical composition of the soil. A comparison of these characteristics at ‘control’ and ‘treated’ sites over repeated Methoprene applications enabled the assessment of the non-target impacts of Methoprene on soil mites and soil function.