Quickly, accurately, and easily assessing the efficacy of treatments to control sessile arthropods (e.g., scale insects) and stationary immature life stages (e.g., eggs and pupae) is problematic because it is difficult to tell whether treated organisms are alive or dead. Current approaches usually involve either maintaining organisms in the laboratory to observe them for development, gauging their response to physical stimulation, or assessing morphological characters such as turgidity and color. These can be slow, technically difficult, or subjective, and the validity of methods other than laboratory rearing has seldom been tested. Here, we describe development and validation of a quick easily used biochemical colorimetric assay for measuring the viability of arthropods that is sufficiently sensitive to test even very small organisms such as white fly eggs. The assay was adapted from a technique for staining the enzyme hexokinase to signal the presence of adenosine triphosphate in viable specimens by reducing a tetrazolium salt to formazan. Basic laboratory facilities and skills are required for production of the stain, but no specialist equipment, expertise, or facilities are needed for its use.

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Inspecting for live organisms is the main method used to verify efficacy of phytosanitary treatments. Evaluating whether small, immobile organisms such as eggs, pupae and scale insects are alive or dead usually involves either checking morphological criteria or rearing them to observe development. These methods can be inaccurate, impractical and time consuming; thus, better methods are needed. To evaluate the potential for developing enzyme-based viability assays, we used electrophoretic gels to evaluate postmortem degradation of ten enzymes in Musca domestica L. (Diptera: Muscidae), four in Bemisia flocculosa Gill and Holder (Hemiptera: Aleyrodidae), and seven in Listronotus bonariensis (Kuschel) (Coleoptera: Curculionidae). Fresh insects displayed strong enzyme activity and distinct bands, but dead insects exhibited either no activity or weakened activity with reduced band resolution and increased migration of stained areas. Of ten enzymes investigated, seven showed clear indications of degradation just 1 day postmortem. Polyacrylamide gel electrophoresis of enzymes can be used to evaluate organism viability and has potential for estimating postmortem intervals. We also measured postmortem degradation rates of five M. domestica enzymes by assaying them in solution; these showed constant or gradually declining activity for 28 days postmortem, so live and dead specimens were less easily distinguished. By assaying enzymes in solution, it is possible to develop quick, easily operated tests that can be used outside the laboratory for a variety of quarantine-related purposes.

Quarantine authorities often deal with imported food products containing ingredients of animal origin that can carry biosecurity hazards such as animal diseases The New Zealand Ministry for Primary Industries (MPI) developed an Import Health Standard to manage this risk The standard states that products must be heated to a specified temperature for a specified time (eg 110C for 40 min) within hermetically sealed containers However it can be difficult to verify that products have been properly heattreated and a quick easilyused test would assist with verification Possible targets of such a test are enzymes that are inactivated by high temperatures This paper describes a modified electrophoretic gel stain recipe for glucose6phosphate isomerase (GPI) that enables testing of samples in tubes In these experiments nonheattreated food products rapidly produced a coloured dye after being mixed with stain but heattreated products did not Some imported foods intercepted by MPI were also evaluated There is potential to develop similar tests for use on plant products and/or organisms associated with plant products to verify heat treatment has taken place