Effect of packaging chickpeas with CO2 modified atmospheres on mortality of Callosobruchus chinensis (Coleoptera: Chrysomelidae)

Abstract High CO2 modified atmosphere packaging (MAP) is a sustainable alternative for pest control in stored products. The effectiveness of this method varies depending on the CO2 concentration used, insect exposure time, temperature, humidity, the tested insect species, and the insect's stage of development. One factor that substantially influences the concentration of CO2 available inside the packages, and therefore the effectiveness of the treatment, is the sorption of gas in the commodity. This study evaluated the impacts of packaging chickpeas in modified atmospheres of 50% and 90% CO2 with filling ratios (proportion of grain relative to the volume of the package) of 1% and 96% grain on the mortality of C. chinensis eggs and pupae and on the fecundity of the females emerging from the surviving individuals. In packages with a 96% filling ratio, CO2 concentration in the headspace of packages reduced to 60% and 30% from initial concentrations of 90% and 50% (respectively) in the first 24 h of exposure. Despite this reduction in CO2 concentrations, no differences in the mortality of C. chinensis eggs and pupae were observed between these packages and those with a 1% filling ratio. The estimated exposure time to achieve 95% mortality (LT95) of the eggs ranged from 38 to 68 h; for pupae, it ranged from 142 to 248 h. The fecundity of females that emerged from the surviving pupae decreased after 48 h of exposure to CO2, but the fecundity of females that emerged from surviving eggs was not affected by exposure time, MAPs, or filling ratio. Therefore, effective pest control can be accomplished with the use of sufficient treatment times to eradicate the most tolerant developmental stages, regardless of whether the packages are full or not.