Vol. 9, Issue 6, Part A (2022)

In the Sudan, the indoor residual spraying (IRS) campaigns currently depend on spraying the carbamate insecticide Bendiocarb (2, 2 dimethyl-2H-1,3-benzodioxol-4-yl methyl carbamate; Ficam® 80% WP) at 200 mg/m² against Anopheles arabiensis Patton (Diptera: Culicidae) and other mosquitoes and some household pests. Households building materials in the targeted villages are mainly constructed by using different local materials (wood and straw), mud bricks and a third group use cement in their walls. The residual activity (persistence) of Bendiocarb on the different building substrates/materials (viz. straw, mud, cement), and glass, which is used as non-absorbent substrate was determined. The susceptibility of mosquitoes to Bendiocarb was tested using 5 concentrations (i.e. 80, 40, 20, 10, 5, 2.5 ppm). Ten adults were exposed for 24 hr. to each of these concentrations, which was replicated 4x, and the experiment was repeated twice. The substrates were attached to the wall and Bendiocarb was sprayed as recommended by WHO; WHO recommended bioassay tests were carried out for evaluation using standard WHO cones. The LC50 proved to be 58ppm and LC90 143 ppm, and the slope of log-dose-probability line (Ld-P lines) 3.04. During the first months 100% mortality was obtained for the different substrates. The 2nd month tests showed 100% mortality for all substrates, except cement (92.5% mortality). In the 3rd month, the mortality rate was 100% on straw and glass, but 95% and 87.5% mortality were registered on mud and cement, respectively. The 4th month results were 60, 72.5, 80, and 90% mortality on cement, mud, straw and glass, following the same order. However, after 5 months, the mortality was: 25% for cement, 35% for mud, 42% for straw, and 65% for glass. It is concluded that the cement is the substrate in which the Bendiocarb performance was the lowest of the 4 tested materials. Bendiocarb stayed longer in mud building material, followed by the straw. In the glass substrate, Bendiocarb persisted longer than all the other substrates, which could be attributed to its nature as not absorbent and inert material. Therefore, Bendiocarb should be used as an effective IRS insecticide against A. arabiensis at 200 mg/m² and for the tested building materials, treatment should be at least 2x / yr.