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

Abstract

This study was carried out on the effects of different exposures of UV-C irradiation (253.2 nm) (5, 10, 15, 20 and 25 mins) on the mortality of stored product pests: Sitophilus granarius L. (Coleoptera: Curculionidae) as a primary pest, Tribolium castaneum (Herbst) (Col.: Tenebrionidae) and Cryptolestes ferrugineus (Stephens) (Col.: Laemophloeidae) and Oryzaephilus surinamensis (Ganglbauer) (Col.: Silvanidae) as secondary pests. Besides, the viability of treated maize and wheat seed items influenced by UV-C irradiation was analysed by tetrazolium test. Our results confirmed the treatment that leads to total mortality is inversely proportional to the exposure to UV-C radiation. The time of total mortality during the post-treatment period as a function of radiation exposure can be characterised by a power-like trend line for each examined insect species. Our results confirmed the insecticidal efficacy and the sensitivity of pest species with different ecological functions to UV-C irradiation. The primary species in the crop treated by shorter exposure (10 mins of UV-C at a distance of 22 cm) may prevent the introduction of secondary stored product pests enter later. The tetrazolium test showed that the wheat seeds were more sensitive to this physical stress than maize seeds in a similar condition. Values of the recorded viabilities fluctuated highly. The effects of UV radiation on treated wheat and maize seeds are somewhat controversial. However, this pest elimination technique is primarily recommended in environments exempt from viable stored seeds because the intactness of treated seeds cannot be demonstrated.