Ecological Interactions of Predatory Mites, Cheyletus eruditus (Schrank) (Trombidiformes: Cheyletidae) and Cheyletus malaccensis Oudemans, and Prey, Liposcelis decolor (Pearman) (Psocodea: Liposcelididae), under Different Thermo-Hygrometric Regimes

SIMPLE SUMMARY: Psocids are stored-product pests that are difficult to manage even with the most potent pesticides, including phosphine. Predatory mites, Cheyletus eruditus and Cheyletus malaccensis, are frequently found associated with pestiferous arthropods in storage environments and can be potential natural enemies for use in stored grain integrated pest management (IPM) systems against psocids. This study aimed to provide quantitative data demonstrating the biological control potential of C. eruditus and C. malaccensis for managing the psocid species Liposcelis decolor in laboratory simulated-storage conditions. Prey population suppression (or percentage prey survival—both refer to extent of decrease (change) in prey population) and progeny replacement efficiency of the predators were assessed under different predator–prey ratios (0:20, 1:20, 2:20, 4:20, and 10:20), temperatures (20, 24, 28, and 32 °C), and relative humidities (RH) (63, 75, and 85%) over 40 days under laboratory conditions of 0:24 (L:D) photoperiod. The results showed that C. eruditus and C. malaccensis can prey on L. decolor to survive, establish, and produce significant numbers of offspring (~96.7–844.4% fold) and caused L. decolor population suppression of ~67.1–97.2% for the predator–prey ratios of 1:20, 2:20, 4:20, and 10:20, temperatures of 20, 24, 28, and 32 °C, and RH levels of 63, 75, and 85%. The levels of psocid population suppression achieved indicate the great potential of both predatory mites for psocid management. ABSTRACT: Predator–prey interactions are linked through trophic relationships, and individual population dynamics are a function of multiple interactions among many ecological factors. The present study considered the efficacy of the predatory mites Cheyletus eruditus (Schrank) (Trombidiformes: Cheyletidae) and Cheyletus malaccensis Oudemans to manage Liposcelis decolor (Pearman) (Psocodea: Liposcelididae). Prey population suppression and progeny replacement efficiency of the predators were assessed under different predator–prey ratios (0:20, 1:20, 2:20, 4:20, and 10:20), temperatures (20, 24, 28, and 32 °C), and relative humidities (RH) (63, 75, and 85%) over 40 days under laboratory conditions of 0:24 (L:D) photoperiod. Suppression of L. decolor population when C. eruditus-related predator-to-prey ratios of 1:20, 2:20, 4:20, and 10:20 were used was ~61.7, 79.7, 85.1, and 87.5%, respectively, relative to the Control ratio (0:20). In the case of C. malaccensis, suppression of 70, 82.1, 92.9, and 96.5%, respectively, was achieved. Although the low 63% RH limited efficacy of these cheyletid mites, both predatory mites caused pest population suppression of ~67.1–97.2% and increased their progeny by ~96.7–844.4% fold for the predator–prey ratios of 1:20, 2:20, 4:20, and 10:20, temperatures of 20, 24, 28, and 32 °C, and RH levels of 63, 75, and 85%. The levels of psocid population suppression achieved indicate the potential of both predatory mites for psocid management.