Biological Performance of Certain Botanical Fine Dusts, Ash and Sulfur Powders against the Rice Weevil Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

Abstract

Five botanical fine dusts, ash and sulfur powders were tested for their biological performance activity against the rice weevil Sitophilus oryza. Their toxicities and delayed effect on the treated insect were determined. The insect was exposed to treated rice grain with each of the evaluated materials and bioassayed for different intervals extended form 3 to 30 days. The insecticidal activity was expressed in terms of the adult insects-mortality due to the contact with the tested materials. The effect of these materials on the inspected damage in rice grains and/or resulted F 1 progeny post-treatment had been investigated and expressed in terms of productivity inhibition percentage (PIP).The complete control of treated insects (100% kill) was recorded at the doses of 0.25 and 0.5 g of black pepper fine dust/50 g rice grains after 21 and 14 days post exposure, consequently. Furthermore, at the higher dose of 0.5 g material/50 g rice grains, camphor and black pepper pronounced complete control of the exposed adult-insects giving 100% kill after an exposure period of 30 days, while Latania fine dust was the least efficient tested material.The results were also confirmed by the deduced dependent positive strong relationship between the recorded insect mortality and the time needed to cause 50 % kill of the exposed insects (LT 50 ) at all the different used doses. Based on LT 50 values, the superior insecticidal effect was recorded for black pepper, followed by orange peel, then camphor and the other tested materials. Meanwhile, clove and Latania fine dusts were the least efficient materials at all used doses (w/w).The results proved that camphor fine dust was the most potent material in preventing grains perforation and reducing the damage that can be caused by the adultweevils of S. oryzae followed by black pepper fine dust. Although, the clove fine dust was less toxic, it showed a potent delayed and completely inhibited the raise of F 1 progeny post-parents treatment (100%) at its higher tested dose of 0.5 g powder /50 g rice. There was also a good correlation between the insecticidal activity of black pepper fine dust, either picked up or contacted the exposed insects and its effect on prevention or reduction of grains damage and/or its ability in suppressing the raised individuals of F 1 progeny.