Insecticides applied to soil for the control of small hive beetle 'Aethina tumida' Murray (Coleoptera: Nitidulidae) larvae

A laboratory bioassay was developed to measure the response of full-size Small Hive Beetle, 'Aethina tumida' Murray larvae to insecticidal soil treatments. Formulated products diluted in water were sprayed onto the surface of 15 cm columns of soil contained in 9 cm diameter plastic tubes prior to the release of larvae onto the soil surface or onto soil already containing pre-pupae. Chlorpyrifos (Lorsban), permethrin (Permex) and imidacloprid (Premise) were the most effective of the insecticides tested. Trials with permethrin and imidacloprid demonstrated that treatments were effective irrespective of whether larvae were placed onto previously treated soil or were present in the soil before spray application. The persistence activity of permethrin and imidacloprid in soil was measured by exposing treated soil to ambient weather. In one trial, toxicity to beetle larvae diminished with time. However, in a second trial, where heavier rainfall was recorded, effectiveness was maintained at a high level throughout the 89 days post-treatment interval. This suggests that rainfall influences soil moisture content which in turn presumably assists contact between larvae and insecticide residues.