Relative toxicity of permethrin to Mononychellus progresivus Doreste and Tetranychus urticae Koch (Acari: Tetranychidae) and their predators Amblyseius limonicus Garman & McGregor (Acari: Phytoseiidae) and Oligota minuta Cameron (Coleoptera: Staphylinidae): bioassays and field validation

Feasibility of using permethrin for predator-exclusion experiments was studied in the Cauca Valley region of Colombia. Impact of permethrin on the cassava pests, Mononychellus progresivus Doreste and Tetranychus urticae Koch; their natural enemies. Amblyseius limonicus Garman & McGregor (formerly in Typhlodromalus) and Oligota minuta Cameron; and the sympatric pest, Phenacoccus herreni Cox & Williams, was determined through laboratory bioassays and field tests. Laboratory LC50 data showed that the predaceous species were more than an order of magnitude more susceptible to permethrin than their prey. Doses for field testing were chosen based on laboratory data. No effect upon P. herreni survivorship or fecundity was measured at the highest dose chosen for field testing. In the field, data were obtained only for A. limonicus and M. progresivus. Plots that received bimonthly treatments with either 2 or 8 g (AI)/100 liters had significantly lower numbers of A. limonicus than untreated plots. M. progresivus numbers began to increase in treated plots immediately after initiation of permethrin application and remained significantly higher than in untreated plots throughout the course of the treatment period.