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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Insect Behavior and Biocontrol Research » Research » Publications at this Location » Publication #324032
Title: Effects of Low-Oxygen Environments on the radiation tolerance of the cabbage looper moth (Lepidoptera: noctuidae)

Author
item CONDON, CATRIONA - University Of Florida
item WHITE, SABRINA - University Of Florida
item Meagher, Robert - Rob
item JEFFERS, LAURA - Animal And Plant Health Inspection Service (APHIS)
item BAILEY, WOODWARD - Animal And Plant Health Inspection Service (APHIS)
item HAHN, DANIEL - University Of Florida

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2016
Publication Date: 2/7/2017
Citation: Condon, C.H., White, S., Meagher Jr, R.L., Jeffers, L.A., Bailey, W.D., Hahn, D.A. 2017. Effects of Low-Oxygen Environments on the radiation tolerance of the cabbage looper moth (Lepidoptera: noctuidae). Journal of Economic Entomology. 110(1):80-86.
DOI: https://doi.org/10.1093/jee/tow273

Interpretive Summary: All insect species, including pests, have bacterial, viral, and fungal diseases. These pathogens, when applied to crop plants, can help manage insect populations. The way that different fungal diseases attack and kill caterpillars is not completely understood. Scientists from the University of Florida and a researcher with USDA, Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, used the caterpillars of two moths, beet armyworm and cabbage looper, to learn more about the sequence of infection of a pathogenic fungal species, Metarhizium rileyi. Results showed that after contact, the caterpillar produces chemicals in response to the fungus. The fungus in turn detects these chemicals and then switches to produce a more invasive and pathogenic stage. Attempts were made to identify the signaling chemicals produced by the caterpillars but they remain unidentified. The findings demonstrate that the relationship between fungus and insect is much more complicated than previously thought and that through a more complete understanding of the pathogenesis will lead to a more effective use of pathogenic fungi to control insect pests.

Technical Abstract: Ionizing radiation is phytosanitary treatment to mitigate risks associated with trade of fresh fruits and vegetables. Commodity producers wish to irradiate fresh product stored in modified atmosphere packaging that increases shelf life and delays ripening. However, irradiating insects in anoxia increases radiation tolerance and regulatory agencies are concerned that modified atmosphere packaging will decrease the efficacy of radiation doses recommended to neutralize insects. Here, we examined how irradiation in a series of oxygen conditions (0.1-20.9 kPa O2) alters the radiotolerance of larvae and pupae Trichoplusia ni (Hübner). Irradiating in anoxia (0.1 kPa O2) increased the radiation tolerance of insects compared to irradiating in atmospheric oxygen (20.9 kPa O2). Our data show that irradiating pharate adult pupae at 600 Gy in 5 kPa O2 increased adult emergence compared to irradiation in atmospheric oxygen (20.9 kPa O2). High doses of radiation (600-800 Gy) prevented the adult emergence of T. ni irradiated during late stage pupal development, and irradiating at 800 Gy sterilized female pharate adult pupa in all oxygen treatments. Our data also show that in one of three cohorts irradiating T. ni larvae in severe hypoxia (5 kPa O2) can also increase radiotolerance at intermediate radiation doses compared to irradiating in atmospheric oxygen conditions. We discuss the implications of our results for the current generic doses for phytosanitary irradiation and the temporary restriction on irradiating commodities in modified atmosphere packaging that reduces the atmosphere to less than 18 kPa O2.