Impact of UV-C irradiation on storage pests with different ecological functions and the viability of the treated grains

This study was carried out to investigate the effect of different exposures of UV-C radiation (253.2 nm) (5, 10, 15, 20 and 25 mins) on the mortality of adult stages of four stored product pests: Sitophilus granarius L. (Coleoptera: Curculionidae) as a primary pest, Tribolium castaneum (Herbst) (Col.: Tenebrionidae), Cryptolestes ferrugineus (Stephens) (Col.: Laemophloeidae) and Oryzaephilus surinamensis (Ganglbauer) (Col.: Silvanidae) as secondary pests. Additionally, the viability of treated maize and wheat grains influenced by UV-C radiation (10 mins of UV-C at a distance of 22 cm) was analyzed by using a tetrazolium test. Insect rearing was carried out at 26 ± 2°C, 60 ± 7% RH, 16/8 photoperiod. Our results confirmed that a longer exposure (25 min.) to UV-C corresponded with higher mortality over time. In the elapsed time after radiation treatment as a function of exposure, the mortality was characterized by a power trend line for each examined insect species. S. granarius, as the primary stored product pest, in the crop treated by shorter exposure may prevent subsequent infestation of secondary stored product pests (T. castaneum, C. ferrugineus, O. surinamensis). The tetrazolium test showed that wheat seeds were more sensitive to UV-C radiation than maize seeds. This pest elimination technique is primarily recommended in environments exempted from viable stored seeds. UV-C irradiation of stored products could be an effective non-chemical practice against arthropod pests that move on the surface.