A MICROENCAPSULATED FORMULATION OF LAMBDA-CYHALOTHRIN

Abstract:
Demand CS® (lambda-cyhalothrin) has been designed specifically for use in urban pest management. The product is based on microencapsulation technology which encloses the liquid active ingredient in a polymer shell to provide protection against hostile environmental conditions. Electron microscopy and biological assays revealed that capsules remain intact for several months on a range of surfaces and provide control of pests including mosquitoes (Aedes aegypti) and cockroaches (Blattella germanica). The polymer wall retains the lambdacyhalothrin for extended periods on inert or chemically active surfaces, reducing losses from adsorption and chemical reaction. However, when an insect picks up a capsule, its contents rapidly diffuse into the lipophilic insect cuticle, leading to rapid knockdown and mortality. Laboratory assays demonstrated that an insect can pick up large numbers of microcapsules from a treated surface, many more than are needed to kill it. Bioassays also provided evidence that contact between social or gregarious insects, such as ants or cockroaches, allows transfer of capsules between individuals with the result of increasing the lethal effect to insects not directly exposed to the treated surface. With the active ingredient not immediately available to the insect, cockroaches and ants were able to pick up a lethal dose of insecticide before any sub-lethal effects could occur. Other effects such as a marginally slower knockdown speed compared to WP or EC formulations were observed, in addition to a reduced flushing effect. The need for formulations specifically designed for use in the urban and household market is highlighted.