Phytosanitary irradiation: Does modified atmosphere packaging or controlled atmosphere storage creating a low oxygen environment threaten treatment efficacy?

Abstract

Phytosanitary irradiation treatment is used to control insects in fresh commodities so that the commodities can be safely exported to pest-free areas. The goal of phytosanitary irradiation is to prevent reproduction. Modified atmosphere packaging (MAP) and controlled atmosphere (CA) storage creating a low oxygen environment are used to preserve the quality of fruits and vegetables. Low oxygen is known to be radioprotective in insects and other organisms. This raises the question of whether MAP or CA may reduce the efficacy of phytosanitary irradiation treatments. IPPC regulations prohibit the application of phytosanitary irradiation for fruits and vegetables under modified atmospheres. Studies used to support this restriction have typically used unrealistic conditions, particularly with the use of severe hypoxia or anoxia and short duration exposures after irradiation (≤2 h hold time under low oxygen). Results from these studies have been extrapolated to suggest phytosanitary irradiation may be compromised by MAP or CA. Although low oxygen radioprotection in insects has been demonstrated for various biological parameters such as adult emergence, flight ability, mating success, and fertility, to date no studies have shown that irradiation of insects at approved doses under modified atmospheres results in treatment failure, i.e., allows successful reproduction. Recent studies using commercially relevant conditions show that MAP may improve control due to the toxic effect of extended exposures to low O2 and high CO2 to insects. Regulatory restrictions on the use of MAP and CA during irradiation treatment should be reviewed and reconsidered. In the absence of data showing treatment failure due to modified atmospheres, current regulatory restrictions are not scientifically justified.