Biological control of pests of stored cereals with the predatory mites Blattisocius tarsalis and Cheyletus malaccensis

Numerous arthropod pest species can cause significant losses in the quantity and quality of stored products. Currently, the most common pest control strategy is the use of a limited number of authorized synthetic insecticides. However, the overuse of these insecticides has led to an increase in pesticide resistance, reducing their effectiveness. Biological control using natural enemies offers an effective alternative to prevent insect populations from reaching pest status. Generalist predatory mites are noted for their potential as biocontrol agents as they can prey on a large variety of pest species and are easy to manage and apply. We evaluated the suitability of three predatory mites, Blattisocius tarsalis, Cheyletus malaccensis, and Amblyseius swirskii, for controlling several insect pests that are usually present in stored cereals. Prey acceptance and predation rates were assessed in experiments in which a known number of preys were offered to mite females in different arenas. Blattisocius tarsalis and C. malaccensis exhibited broad polyphagous behavior on insect pests commonly found in stored rice and other cereals. In contrast, A. swirskii was ineffective against these pest species. The efficacy of B. tarsalis and C. malaccensis, individually or in combination, in controlling populations of Oryzaephilus surinamensis and Sitotroga cerealella in medium-size arenas was also evaluated. Whether individually or in combination, both predatory mites reduced populations of O. surinamensis or of S. cerealella by half. These results suggest that periodic releases of these predatory mites could maintain these pest populations under control.