LABORATORY TESTS ON INSECTICIDAL EFFECTIVENESS OF DISODIUM OCTABORATE TETRAHYDRATE, DIATOMACEOUS EARTH AND AMORPHOUS SILICA GEL AGAINST Sitophilus oryzae (L.) AND THEIR EFFECT ON WHEAT BULK DENSITY

Sa？etak We examined insecticide effectiveness of three different inert dusts: disodium octaborate tetrahydrate (DOT) and diatomaceous earth (DE) Celatom？ Mn 51 applied as powder and suspension, and silica gel Sipernat？ 50 S applied as powder against Sitophilus oryzae (L.) and their reduction of grain bulk density. Sipernat？ 50 S was the most effective dust with a very fast initial effectiveness. DE and DOT generated similar effectiveness against S. oryzae. DOT generated low initial effectiveness but after prolonged exposure time of 8 and especially after 21 days, the mortality was very high (100%), similar to the effectiveness of DE. The similar order of dusts was obtained in the reduction of wheat bulk density. Applied at dose of 200 and 500 ppm, the lowest bulk density difference in regard to bulk density of untreated wheat had DOT (-1.1 and -1.9 kg hl-1, respectively), followed by Celatom？ Mn 51 (-3.5 and -4.3 kg hl-1, respectively) and Sipernat？ 50 S (-5.2 and -5.5 kg hl-1, respectively). Due to the effect on wheat bulk density DOT belongs to the group with the least negative effect on bulk density and therefore, it is a promising dust to control stored grain insect pests