Laboratory studies evaluating the efficacy of diatomaceous earths, on treated surfaces, against stored-product insect and mite pests

The efficacy of dry dust and slurry applications of Silico-sec® and Diasecticide™, applied to glass and plastic surfaces, was assessed in the laboratory against the beetles Tribolium castaneum, Sitophilus granarius and Oryzaephilus surinamensis, the mites Acarus siro and Lepidoglyphus destructor, and against larvae of the moth Ephestia kuehniella. For the insects, doses of 5, 10 and 20 g/m2 were evaluated for all preparations, while for the mites 0.5, 1 and 2 g/m2 of the dry dusts, and 2.5, 5 and 10 g/m2 of the slurries were assessed. Mortality was evaluated after 7 days and 24 h for the insects and mites, respectively, in conditions of 15 °C and 80% r.h., chosen to represent typical UK conditions immediately after harvest. The Silico-sec® dry dust was the most effective treatment with mean mortalities ranging from 93-100% for all the pest species at all doses. The Diasecticide™ dry dust was ineffective against T. castaneum and S. granarius with mean mortalities ranging from 86-98% for the other species at the highest dose. With both DEs the slurry applications were generally less effective than the dry dusts at equivalent doses. Oryzaephilus surinamensis was the least tolerant insect species and S. granarius and T. castaneum the most tolerant. The mite A. siro was less tolerant than L. destructor.