Critical PO2 as a diagnostic biomarker for the effects of low-oxygen modified and controlled atmospheres on phytosanitary irradiation treatments in the cabbage looper Trichoplusia ni (Hubner)

Authors: CHEN, CHAO - University Of Florida; CONDON, CATRIONA - University Of Florida; BOARDMAN, LEIGH - University Of Florida; Meagher Jr, Robert; JEFFERS, LAURA - Animal And Plant Health Inspection Service (APHIS); BAILEY, WOODWARD - Animal And Plant Health Inspection Service (APHIS); HAHN, DANIEL - University Of Florida

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2020
Publication Date: 1/30/2020
Citation: Chen, C., Condon, C.H., Boardman, L., Meagher Jr, R.L., Jeffers, L.A., Bailey, W.D., Hahn, D.A. 2020. Critical PO2 as a diagnostic biomarker for the effects of low-oxygen modified and controlled atmospheres on phytosanitary irradiation treatments in the cabbage looper Trichoplusia ni (Hubner). Pest Management Science. https://doi.org/10.1002/ps.5768.
DOI: https://doi.org/10.1002/ps.5768

Interpretive Summary: Irradiation of plant material (phytosanitary irradiation) is an acceptable alternative to chemical fumigants for disinfesting fresh commodities from insect pests. However, regulatory agencies are concerned that packaging of products under low-oxygen conditions could reduce the efficacy of phytosanitary irradiation. One hurdle slowing the widespread application of phytosanitary irradiation is a lack of knowledge about how moderate levels of low oxygen may affect treatments. Using the cabbage looper moth as the test species, scientists at the University of Florida, in collaboration those with USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, and USDA-APHIS-PPQ, assessed the critical levels of oxygen at which an insect’s metabolism becomes impaired. The findings established the oxygen levels at which radioprotection interfered with the phytosanitary irradiation. This study is a critical step in providing the criteria necessary to establish phytosanitary irradiation as an effective alternative control treatment for disinfesting fresh commodities.

Technical Abstract: Using the cabbage looper Trichoplusia ni (Hübner), we show that there is a substantial increase in radioprotection when larvae are irradiated in atmospheres more hypoxic than their Pcrit (3.3 kPa O2). These data are consistent with our hypothesis that the Pcrit could be used as a diagnostic biomarker for what levels of hypoxia may induce radioprotective effects that could impact phytosanitaary irradiation treatments. We propose that the relationship between Pcrit and radioprotective effects could allow us to build a framework for predicting the effects of low-oxygen atmospheres on the efficacy of phytosanitary irradiation. However, more widespread studies across pest species are still needed to test the generality of this idea.