A rapid and non-destructive method to discriminate irradiated Ceratitis capitata (Diptera: Tephritidae) using near-infrared spectroscopy

Authors: Liang, Peishih; Follett, Peter; Mason, Charles

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2026
Publication Date: 4/17/2026
Citation: Liang, P., Follett, P.A., Mason, C.J. 2026. A rapid and non-destructive method to discriminate irradiated Ceratitis capitata (Diptera: Tephritidae) using near-infrared spectroscopy. Journal of Economic Entomology. 119(3):2128-2135. https://doi.org/10.1093/jee/toag090.
DOI: https://doi.org/10.1093/jee/toag090

Interpretive Summary: The Mediterranean fruit fly (medfly) is a major cosmopolitan pest presenting as a significant threat to United States agriculture. One primary control method is Sterile Insect Technique (SIT), which involves area-wide release of the sterile males that mate with wild females, resulting in no offspring and population decline. A key component of SIT quality assessment is marking sterile male pupae with a fluorescent external marker dye, which allows identification of SIT flies among those caught in monitoring traps. While the marking procedure is simple, screening trapped flies by squishing their heads to detect the dye is labor intensive. In this study, we evaluated the feasibility of using near-infrared (NIR) spectroscopy, a well-established technique for rapid and non-destructive analysis of chemical and physical properties, to differentiate SIT medfly from non-SIT flies. Full NIR spectrum of over two thousand medfly males were measured, processed, and analyzed using classical machine learning methods, achieving total accuracy of 84.2%. The positive results demonstrate that NIR spectroscopy can be used to identify SIT medflies non-destructively without external dye markers.

Technical Abstract: The Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is a major cosmopolitan pest presenting as a significant threat to United States agriculture. For pest management, Sterile Insect Technique (SIT) is an environmentally-friendly method involving the mass-rearing and sterilization of a target pest using radiation, followed by the systematic area-wide release of the sterile males, where they mate with wild females resulting in no offspring and a declining pest population. To assess the quality and effectiveness of medfly SIT releases, mass-reared pupae are mixed with a fluorescent pink or orange external marker dye that will transfer to the adults upon emergence from the pupal casing. The dye, which fluoresces when exposed to ultraviolet light, is used to identify the flies as sterile, differentiating them from wild flies. While the marking procedure is simple to apply, the screening process can be labor intensive. In this study, we evaluated the feasibility of using near-infrared (NIR) spectroscopy, a well-established technique for rapid and non-destructive analysis of chemical and physical properties, to differentiate irradiated medfly from non-irradiated ones. Full NIR spectrum (900 nm to 2500 nm) of 1,212 irradiated and 1,061 non-irradiated mass-reared Vienna 7 medfly males were measured using a benchtop spectrometer coupled with a backscatter optical fiber probe. The data was processed and analyzed using classical machine learning methods. A total classification rate (i.e. overall accuracy) of 84.2% for classifying irradiated and non-irradiated medflies was achieved using 11-point Savitzky-Golay 2nd derivatives. Total classification rates of 92.8% and 88.6% were achieved for samples that were seven to 16 days old and older than 17 days, respectively. These results demonstrate that the irradiated medfly phenotype can be differentiated from samples within the same rearing line. Further refinement of this technique for field use in SIT program areas and expansion to other tephritid species should be investigated based on the successful outcome of this study.