Enhanced-Efficacy Iranian Diatomaceous Earth for Controlling Two Stored-Product Insect Pests

The present study was conducted to evaluate the insecticidal activity of three diatomaceous earth (DE) products, SilicoSec (Biofa GmbH, Munsingen, Germany), Protect-It (Hedley Technologies Inc., Canada), and Mamaghan. The silica aerogel was mixed to enhance the efficacy of Mamaghan DE with 10, 15, and 20% rates. The DE products were applied at treatment rates of 100, 200, and 400 ppm against adults of Tribolium confusum Jacquelin du Val. (Coleoptera: Tenebrionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae). In the second experiment, 0.1 and 0.5% deltamethrin was added to Mamaghan DE-10% silica aerogel to enhance the activity of the DE. Adult mortality was recorded 2, 5, 7, 10, and 14 d after exposure. Parental adults were removed after 14-d exposure time and progeny developed was evaluated after 65 d. Mamaghan-15 and 20% silica aerogel caused the highest mortality (>97%) against T. confusum after 10 d of exposure at the highest dose of 400 ppm which exceeded to 100% mortality after 14 d. However, the toxicity of Mamaghan DE against R. dominica was lower than that of the two commercial formulations at all dose rates. The presence of 0.1% deltamethrin increased the insecticidal activity of Mamaghan DE and significantly suppressed progeny production of both species. Even at the lowest dose of Mamaghan-10% + 0.1% deltamethrin, progeny production of both species was very low (four or less individuals per vial). However, no progeny was recorded in Mamaghan-10% + 0.5% deltamethrin. Thus, adding low rates of silica aerogel and deltamethrin considerably enhanced the efficacy of Mamaghan DE in controlling T. confusum and R. dominica.