Enhanced fumigant toxicity of allyl acetate to stored-product beetles in the presence of carbon dioxide

Toxicity of allyl acetate (5-25 mg/l doses) to mixed-age cultures of stored-product beetles including Cryptolestes ferrugineus, Lasioderma serricorne, Oryzaephilus surinamensis, Rhyzopertha dominica, Sitophilus oryzae and Tribolium castaneum in the presence of carbon dioxide (CO2) (10% and 20%) with a 48-h exposure period was studied in the laboratory at 27±2 °C. Depending on dosage and the insect species, the fumigant toxicity of allyl acetate was enhanced by CO2. At most of the allyl acetate+CO2 combinations, increased mortality was observed in C. ferrugineus, O. surinamensis and S. oryzae. In L. serricorne and T. castaneum, which are tolerant to allyl acetate, higher mortality due to CO2 was achieved at selected dose combinations only (e.g. 15 mg/l allyl acetate+20% CO2). Significant increase in mortality of R. dominica (the most susceptible species to allyl acetate) exposed to allyl acetate in the presence of CO2 was not evident except at the lower dose of 5 mg/l allyl acetate+CO2 that caused 31.7% mortality. The mortality data show that CO2 could be used as an adjuvant for allyl acetate.