Lethal effects of CO₂-modified atmospheres for the control of three Bruchidae species

Bruchid beetles are important pests of field and stored legumes, causing great economic losses. The main pest species are Callosobruchus maculatus, Acanthoscelides obtectus and Zabrotes subfasciatus. Modified atmospheres (MAs) with high carbon dioxide (CO₂) content are environmentally friendly pest control methods for stored products. They are effective in controlling a wide range of species and can be used to treat different food products without leading to an accumulation of toxic residues. The present study aimed to establish the efficacy of using MAs with high CO₂ to control all developmental stages of these three bruchid pest species. Three high CO₂ MAs (50%, 70% and 90%) were tested at 28°C. In general, pupae and/or eggs were the most tolerant stages to hypercarbia, while adults were less tolerant. The susceptibility of eggs varied greatly according to their phase of development and the pattern was different in the three species tested. Tolerance of other stages to CO₂ also varied among the three bruchid species. To achieve total mortality of Z.subfasciatus, a maximum of 9-11 days were needed, depending on CO₂ concentration, to kill the eggs. This stage and the pupae were the most tolerant stages. However, in A.obtectus and C.maculatus, only pupae were the most tolerant and required 9 days to be killed, their eggs being more sensitive to CO₂.