New thinking for filth fly control: residual, non-chemical wall spray from volcanic glass

Filth flies are of medical and veterinary importance because of the transfer of disease organisms to animals and humans. The traditional control methods include the use of chemical insecticides. A novel mechanical insecticide made from volcanic glass and originally developed to control mosquitoes (Imergard™ WP; ImG) was investigated for control of adult grey flesh flies, Sarcophaga bullata (Parker), secondary screwworms, Cochliomyia macellaria (F.), and house flies, Musca domestica L. In a modified WHO cone test device, the time to 50% mortality (LT₅₀ ) when applied at 5 g/m² (tested at 30 °C and 50% relative humidity (rH)) was 7.1, 4.3 and 3.2 h, respectively. When knockdown was included, the LT₅₀ s were 5.5, 1.5 and 2.8 h, respectively. Application rates of 1.25 and greater g/m² had the shortest LT₅₀ s. The time to the LT₅₀ increased for M. domestica as rH increased, but ImG was still active at the highest rH tested of 70%. Scanning electron micrographs showed ImG was present on all body parts, unlike that for mosquitoes where it was found mostly on the lower legs. These first studies on the use of Imergard WP against flies suggest this could be an alternative method for filth fly control.