Low O2 and high CO2 atmospheres have no impact on efficacy of phytosanitary irradiation doses for Drosophila suzukii larvae

Abstract

Use of irradiation as a phytosanitary treatment has been restricted in atmospheres with low O2 because extreme low O2 exposure can potentially induce radioprotective responses and enhance survival after irradiation. In addition to being low in O2, many controlled atmosphere treatments and modified atmosphere packaging materials maintain high CO2 levels along with low O2. Few studies have combinatorically tested the combined effects of high CO2 and low O2 on radiation sensitivity, and none have done so in a fully factorial design. Here we exposed larvae of the fly Drosophila suzukii to a range of concentrations of low O2 and high CO2 at a series of radiation doses up to 60 Gy. We found that low levels of O2 (≤ 5 kPa) induced a radioprotective response, with the radioprotective response greatest at the lowest O2 concentrations (2.5 & 0 kPa). Adding CO2 significantly decreased this protective response of low O2 on healthy adult emergence when O2 was 2.5 & 5 kPa, but this effect was only apparent at lower radiation doses, well below those used for phytosanitary treatments for this pest. Our study suggests that either controlled atmospheres or modified atmosphere packaging will not challenge the efficiency of phytosanitary irradiation for D. suzukii, and that high CO2 may act as an additional mitigation measure to disinfest insect pests from fresh commodities.