Evaluating flight performance of mass-reared and irradiated navel orangeworm (Lepidoptera: Pyralidae) for sterile insect technique

Authors: REGER, JOSHUA - University Of California; WENGER, JACOB - California State University; BRAR, GURREET - California State University; Burks, Charles - Chuck; WILSON, HOUSTON - University Of California

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2021
Publication Date: 6/9/2021
Citation: Reger, J., Wenger, J., Brar, G., Burks, C.S., Wilson, H. 2021. Evaluating flight performance of mass-reared and irradiated navel orangeworm (Lepidoptera: Pyralidae) for sterile insect technique. Journal of Economic Entomology. Available: https://academic.oup.com/jee/advance-article/doi/10.1093/jee/toab114/6295457. https://doi.org/10.1093/jee/toab114.
DOI: https://doi.org/10.1093/jee/toab114

Interpretive Summary: The navel orangeworm (NOW) is the principal insect pest of pistachios and almonds, crops planted on approximately 1.5 million acres and worth > $8 billion annually. Following the eradication of the pink bollworm, the USDA Phoenix Mass Rearing Facility (MRF) has been funded for >$5 million annually in support of a pilot project examining sterile insect technique for control of NOW through mass-release of sterile irradiated moths in California almonds and pistachio orchards. A flight mill study comparing the flight ability of navel orangeworm shipped from the MRF with or without irradiation with either moths produced locally in California from either the Phoenix strain or a local strain found more non-fliers among shipped moths regardless of sex or irradiation status. Shipped males performed significantly worse in most flight measures than both Phoenix and local strain males reared locally regardless of irradiation status. Among females, the local strain performed better than both locally-produced and shipped Phoenix strain moths in a couple of light parameters, while in other parameters there was no significant difference in performance between the treatment groups. These findings are consistent with field data concerning relative performance of males and females, and provide important support to a growing body of evidence indicating that addressing the impact of collection, handling, and shipping on males is the most immediately important factor to improving performance of sterile NOW in the pilot control program.

Technical Abstract: Navel orangeworm (Pyralidae: Amyelois transitella) is a key pest of almonds and pistachios in California. Moths directly infest nuts which leads to reduced crop yield and quality, and infestation can predispose nuts to fungal pathogens that produce aflatoxins. While several integrated pest management strategies have been developed for A. transitella, studies have recently been initiated to explore the use of sterile insect technique (SIT) as an additional control tool. Mass-rearing, sterilization and transportation methods originally developed for Pectinophora gossypiella (Lepidoptera: Gelechiidae) are currently being used for production of A. transitella in a mass-rearing facility, but the impacts of these processes on performance of A. transitella remain unclear. In this study, computerized flight mills were used to evaluate multiple flight parameters of mass-reared and irradiated A. transitella males and females relative to non-irradiated mass-reared moths and two strains of locally reared moths which were neither mass-reared nor irradiated. Mass-reared non-irradiated females performed similarly to both strains of locally reared females, flying a mean 9.4-11.8 km per night, whereas mass-reared and irradiated females and males and mass-reared non-irradiated males all flew shorter distances, in the range of 3.0-6.7 km per night. All of the mass-reared moths had significantly more non-fliers that did not engage in more than two minutes of continuous flight. Findings from this study suggest that mass rearing conditions reduce A. transitella flight capacity, while irradiation interacts with moths in a sex specific manner.