The effect of ultraviolet C radiation on stored-product pests

Abstract

The potential of using ultraviolet C (UVC) radiation as an alternative treatment and hygiene measure in storage premises was investigated in the laboratory. The effect of UVC on development and progeny production was assessed for pest species of the storage beetles Oryzaephilus surinamensis and Tribolium castaneum, and the mites, Acarus siro and Tyrophagus putrescentiae. Photo-reactivation and the effect of indirect exposure were also investigated, as was the effect on spore germination of a mycotoxin-producing fungus Penicillium verrucosum. The ED₉₅ values for O. surinamensis, T. castaneum, T. putrescentiae and A. siro were 96,549, 59,069, 22,014 and 3,802 μJ cm^-2 respectively, when incubated in lighted conditions. There was an indication of a photo-reactivation effect with T. putrescentiae. Limited penetrative ability through substrates was observed at the doses assessed. Complete prevention of spore germination and complete spore destruction of P. verrucosum was achieved at 20,000 and 25,000 μJ cm^-2 respectively. There was no significant difference in the numbers of O. surinamensis, T. castaneum and T. putrescentiae progeny produced by untreated females and females treated with a sub-lethal dose of UVC. However, there was a large degree of variation in the number of progeny produced by individual females. There was a significant reduction in the numbers of A. siro progeny produced by UVC treated females compared to untreated females; however, the majority of females died during the incubation period before any eggs had been laid. Practical applications of UVC within a storage environment may lie in the treatment of structural and equipment surfaces, such as conveyor systems. However, cleaning prior to treatment is an important consideration as UVC has limited penetrative ability.

Keywords: Ultraviolet C radiation; Storage beetle, Mite and fungal pests; Structural treatment; Hygiene
measure.