RESPONDING TO POTENTIAL AND PERCEIVED CASES OF RESISTANCE IN BLATTELLA GERMANICA (L.)

Abstract:
German cockroach (Blattella germanica) control treatment history has rarely been accompanied by resistance monitoring in the field. Consequently, while cockroach 'resistance', receives much publicity, it is a fact that, to date, only a handful of complaints that are due to pyrethroid resistance, have been received. As a result, few sites have been studied for long since any form of management was initiated, so the virtues of theoretically sound resistance management strategies remain unproven, in practice. Where resistance is suspected, or reported, the first step is to confirm the diagnosis. A series of questionnaires and flow charts have been prepared to address the possibility of operational factors, such as poor application, being responsible for control failure. Test kits are then used to quantify the resistance. If confirmed as product failure, the best 'fire-fighting' advice is to switch to an alternative class of active ingredient (AI). Monitoring any changes in the susceptibility profile of B. germanica, in the field, is an essential component of any resistance management strategy. Test kits can provide a measure of phenotypic, physiological tolerance, however the mechanisms that underly resistance, and the possible influence of cockroach behaviour upon the likelihood, frequency and duration of contact with control agents are also extremely important, although they may be more difficult to quantify. At present, the jury has insufficient data to decide in favour of either rotation or mixture, the two most popular approaches to resistance management, as the 'best strategy' for cockroach control. Instead, the Pest control operator (PCO) is best served by having a range of modes of action (chemical, physical and biological) and presentations (eg. residuals, baits) of control agents at his disposal. The key to success lies in implementing preemptive management strategies, instead of waiting until control failure occurs. It is necessary to provide the customer with the combination of a varied range of products with technical assistance and advice for their use. This advice extends to non-chemical measures such as general hygiene and the use of monitoring traps to help target treatments in space and time.