Evaluation of zeolite dusts as grain protectants against Lepinotus reticulatus, Liposcelis decolor, Acarus siro and Stegobium paniceum

Abstract

The insecticidal effect of two zeolite formulations was tested on wheat against adults of Lepinotus reticulatus Enderlein, Liposcelis decolor (Pearman), Acarus siro L. and Stegobium paniceum (L.). The zeolites were tested at four dose rates, i.e., 50, 100, 500 and 1000 ppm (mg per kg of wheat). The bioassays were conducted under laboratory conditions. The vials for A. siro were kept at 22°C, 60–70% relative humidity (r.h.), for psocids were kept at 30°C, 75–80% r.h., and for S. paniceum were kept at 26°C, 65–70% r.h., with continuous darkness. The bioassays were conducted in cylindrical glass vials of 20 ml (beetles and psocids) or 4 ml (mites). There were three replicates for each treatment, whereas each bioassay was repeated three times for S. paniceum and A. siro, whereas for psocids species, there were three vials for each treatment. Each vial was filled with 10 g of wheat for psocids and S. paniceum, and 2 g for A. siro. Afterward, ten adults of each species were placed in each vial, with separate series of vials per species, and all vials were kept at the aforementioned conditions. Mortality was determined after 4, 7, and 14 d of exposure for psocids, 3, 7 and 14 d of exposure for S. paniceum and 14 d of exposure for A. siro. From the species tested, L. reticulatus and S. paniceum were by far the most susceptible species, given that mortality reached 100% after 14 days of exposure. In contrast, for the other two species, mortality rate for L. decolor was 27% and for A. siro was 54% after 14 d of exposure at 1000 ppm, indicating that for these species, rapid rebound of their populations is likely to occur. The current study provides data on the toxicity of zeolites against four stored-product insect species, for which the relative data available were scarce.