Commodity Treatment and Quarantine Entomology Effects of Low-Oxygen Environments on the Radiation Tolerance of the Cabbage Looper Moth (Lepidoptera: Noctuidae) Catriona H. Condon, 1 Sabrina White, 1 Robert L. Meagher, 2 Laura A. Jeffers, 3 Woodward D. Bailey, 4 and Daniel A. Hahn 1,5 1 Department of Entomology and Nematology, University of Florida, Gainesville, FL 32611 (chcondon1@gmail.com; sabrinawhite407@ gmail.com; dahahn@ufl.edu), 2 USDA-ARS, Center for Medical and Veterinary Entomology, Gainesville, FL 32608 (rob.meagher@ ars.usda.gov), 3 USDA-APHIS-PPQ Center for Plant Health Science and Technology, Raleigh, NC 27606 (laura.a.jeffers@ aphis.usda.gov), 4 USDA-APHIS-PPQ Center for Plant Health Science and Technology, Miami, FL 33158 (Woodward.D.Bailey@ aphis.usda.gov), and 5 Corresponding author, e-mail: dahahn@ufl.edu Subject Editor: Lisa Neven Received 13 October 2016; Editorial decision 1 November 2016 Abstract Ionizing radiation is used as a phytosanitary treatment to mitigate risks from invasive species associated with trade of fresh fruits and vegetables. Commodity producers prefer to irradiate fresh product stored in modified atmosphere packaging that increases shelf life and delays ripening. However, irradiating insects in low oxygen may increase radiation tolerance, and regulatory agencies are concerned modified atmosphere packaging will decrease efficacy of radiation doses. Here, we examined how irradiation in a series of oxygen conditions (0.1–20.9 kPa O 2 ) alters radiotolerance of larvae and pupae of a model lepidopteran Trichoplusia ni (Hubner) (Diptera: Noctuidae). Irradiating in severe hypoxia (0.1 kPa O 2 ) increased radiation tolerance of insects com- pared with irradiating in atmospheric oxygen (20.9 kPa O 2 ). Our data show irradiating pharate adult pupae at 600 Gy in moderately severe hypoxia (5 kPa O 2 ) increased adult emergence compared with irradiation in atmo- spheric oxygen (20.9 kPa O 2 ). Our data also show that in one of the three temporal replicates, irradiating T. ni larvae in moderately severe hypoxia (5 kPa O 2 ) can also increase radiotolerance at an intermediate radiation dose of 100 Gy compared with irradiating in atmospheric oxygen conditions, but not at higher or lower doses. We discuss implications of our results in this model insect for the current generic doses for phytosanitary irradi- ation, including the recently proposed 250 Gy generic dose for lepidioptera larvae, and temporary restriction on irradiating commodities in modified atmosphere packaging that reduces the atmosphere to < 18 kPa O 2. Key words: phytosanitary irradiation, modified atmosphere, hypoxia Ionizing radiation is used to treat fresh commodities after harvest to prevent the spread of pest species to new areas. Irradiation damages many components of insect cells and can lead to sterility or death through the accumulation of dominant lethal mutations in DNA (Robinson 2005). Due to this broad mode of action, phytosanitary irradiation treatments can be highly effective against a wide range of insects. Moreover, because phytosanitary irradiation is broadly ef- fective against insect pests, generic doses developed to disinfest one commodity can often be used for the treatment of other fresh com- modities (Hallman 2012). Currently, the United States Department of Agriculture Animal and Plant Health Inspection Service (USDA APHIS) requires a generic absorbed dose of 400Gy to control insect pests that are present on fresh commodities (APHIS 2015). An exception is that the 400Gy ge- neric dose is not recommended for controlling pupae or adults of Lepidoptera, although these life stages are very rarely found in fresh commodities (Hallman et al. 2013a,b). Where tephritid fruit flies are the only pests of concern for a commodity, a generic dose of 150Gy has been approved for use by both the USDA APHIS and the International Plant Protection Convention (IPPC; APHIS 2015, Hallman et al. 2013). Both generic doses are well below the 1 kGy limit approved by the United States Food and Drug Administration for fresh fruit and vegetables (FDA 1986). Additional generic treatment doses are being developed, as growers are increasingly interested in expand- ing international market access of fresh commodities using phytosani- tary irradiation (PI, hereafter; Follett 2009, Hallman et al. 2013a,b). PI is an increasingly attractive treatment for commodity growers because irradiating produce has several advantages over heat, cold, and fumigation treatments, such as allowing riper and thus higher quality fruits to be imported (Hallman 2012). Fresh commodities V C The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com 80 Journal of Economic Entomology, 110(1), 2017, 80–86 doi: 10.1093/jee/tow273 Advance Access Publication Date: 28 December 2016 Research article Downloaded from https://academic.oup.com/jee/article/110/1/80/2726381 by guest on 06 April 2023