The toxicity effects of atmospheres with high content of carbon dioxide with addition of sulphur dioxide on two stored-product pest species: Sitophilus oryzae and Tribolium confusum

Modified atmospheres (MAs) are safe and environmentally friendly alternatives to control pests in stored products. However, to accommodate the requirements of the food industry, the control of insects by aMA can be a too lengthy process. This paper describes the potential of sulphur dioxide as an additive to reduce the long lethal exposure of modified atmospheres (MA) enriched with carbon dioxide for major stored product pests. Specifically, we evaluated whether the addition of SO₂ (0-30,000ppm) to a high-CO₂ content of 70%-95% MA could enhance its insecticidal effect for the control of Sitophilus oryzae and Tribolium confusum. The addition of 15,000ppm and 30,000ppm of SO₂ to 95% CO₂ enhanced control up to 100% in comparison to CO₂ alone for S.oryzae and T.confusum adults when treated for one day in all of the substrates tested. However, the effectiveness of adding SO₂ at reduced contents was lower and depended on the substrate and pest species considered. The addition of SO₂ also increased the mortality of all of the developmental stages of S.oryzae. The increase in mortality with the addition of SO₂ was also observed when included with 70% CO₂. Therefore, the addition of SO₂ can be considered a feasible means of shortening the length of treatment necessary to achieve the control of these two pests using a high-CO₂ MA.