Spatial and seasonal performance of Blattisocius tarsalis in stored grain environments

In large-scale grain storage facilities, various pests can infest stored grain causing significant damage. The predatory mite Blattisocius tarsalis has shown robust dispersal abilities in controlled environments, along with an effective capacity to prey on the eggs of common storage pests. However, its maximum dispersal potential and efficacy in suppressing pest populations under realistic storage conditions remain poorly understood. Furthermore, the impact of temperature fluctuations on its performance has yet to be fully clarified. In this study, two sets of experiments were conducted, one during the summer and the other during the early spring, to evaluate the dispersal efficacy of B. tarsalis released in a large pile of paddy rice. To assess both dispersal and predatory efficacy, eggs of the common storage pest Plodia interpunctella were used as bait. These were placed at varying depths, directions, and distances, up to 4 m from the release point. Our results demonstrate that B. tarsalis can disperse as far as 4 m and effectively control pest populations, irrespective of seasonal conditions. The mites also exhibited a marked preference for moving into the grain mass and away from light sources. Although this study focused on P. interpunctella , which lays eggs on the grain surface, the ability of B. tarsalis to penetrate the grain pile suggests it may also prey on other pest species that oviposit deeper within the grain mass. These findings underscore the potential of B. tarsalis as a sustainable and effective biological control agent in stored-product pest management. • Blattisocius tarsalis dispersed up to 4 m in a large-scale paddy rice facility. • Dispersal capacity remained consistent across contrasting seasonal conditions. • Mites favored dark, grain-covered zones over illuminated, exposed surfaces. • Potential to target pests ovipositing deep within the grain mass. • Increasing mite numbers did not proportionally enhance predation rates.