Efficacy of filter cake and Triplex powders from Ethiopia applied to concrete arenas against Sitophilus zeamais

Abstract

Filter cake and Triplex are powdered by-products of aluminum sulfate and soap factories, respectively. The latter powder is from berries of the Endod plant, Phytolacca dodecandra L. This study was designed to determine the chemical composition of these two powders using scanning electron microscopy conjugated with energy-dispersive X-ray spectroscopy. Another aim was to evaluate their direct contact toxicity to the maize weevil, Sitophilus zeamais Motschulsky, a common pest of stored grains in Ethiopia. Contact toxicity against S. zeamais was determined by exposing 10 adults for 4, 8, 12, and 24 h in 9 cm diameter concrete arenas inside Petri dishes dusted with filter cake and Triplex at each of the six concentrations (0, 2.5, 3.75, 5, 7.5 and 10 g/m2). Each concentration and exposure time combination was replicated five times. After the intended exposure time, adults were transferred to 150-ml round plastic containers with 30 g of organic hard red winter wheat and held at 28 °C and 65% r.h. for 7 d to determine mortality. Adult progeny production, percent of insect damaged kernels, and grain weight loss at each powder-concentration-time combinations were determined after 42 d. Both powders were free of heavy metals. Silicon and oxygen were the major components of both powders. The 7-d mortality was 100% after a 24 h exposure to 7.5 g/m2 concentration of filter cake and 10 g/m2 of both powders. Reductions in adult progeny production, percent of insect damaged kernels, and grain weight loss were greater when S. zeamais adults were exposed to the powders for longer time periods at higher than lower concentrations. This is attributed to greater mortality at increasing concentrations and exposure times. Our results indicate that filter cake and Triplex can be used to treat concrete surfaces of warehouses and storage structures to control S. zeamais.