Ozone Efficiency on Two Coleopteran Insect Pests and Its Effect on Quality and Germination of Barley

SIMPLE SUMMARY: Rhyzopertha dominica (Fabricius) and Tribolium castaneum (Herbst) are notorious global pests, destroying various stored grains, including barley, wheat, oats, maize, and rice. Ozone (O(3)) is a promising fumigant to control pests in stored grain since it can safely and rapidly auto-decompose without leaving residues, however, relatively few studies have focused on the toxicity of O(3) on stored grain pests in stored barley. In this study we not only explored the susceptibility of all life stages of R. dominica and T. castaneum in barley seeds to different durations of gaseous O(3), but also investigated the effect of O(3) on germination ability, seedling growth, and quality of barley. O(3) was effective against all life stages of two species in barley under sufficient exposure times without negative impacts affecting the commercial quality of barley. However, the germination ability and seedling growth were adversely impacted at longer O(3) exposure times. Thus, it is imperative to select an optimal O(3) exposure time to achieve the desired functional outcome, such as malting, animal feeding, and human consumption. ABSTRACT: Ozone (O(3)) is a potential fumigant to control pests in stored grain since it can safely and rapidly auto-decompose without leaving residues. In this study, the efficacy of O(3) on all life stages of Rhyzopertha dominica (Fabricius) and Tribolium castaneum (Herbst) in barley and the physiological effects on barley and its quality were investigated. Complete control of all life stages of pests was obtained at 700 ppm for 1440 min of ozone exposure without negatively impacting the contents of soluble protein, moisture content, seed colour, hardness, and the weight of thousand barley seeds. The eggs and pupae of these two insects were the more tolerant stages than their larvae and adults. Prolonged exposure times (40 to 1440 min) and mortality assessment intervals (1, 2, and 7 days) increased O(3) efficacy due to the reaction characteristics and delayed toxicity. Aging barley seeds appeared to be more sensitive to prolonged ozone duration than new seeds. A total of 20 and 40 min could promote germination rate, and longer O(3) exposure (1440 min) was unfavourable for germination and seedling growth. Thus, it is imperative to select an optimal O(3) exposure time to transfer ozone into quality contributors of final products and achieve the desired functional outcomes.