Effectiveness of Chlorpyrifos, Fenthion, Malathion, and Propoxur as Screen Treatments for Control of Culicoides mississippiensis12

Chlorpyrifos, fenthion, malathion, and propoxur were tested at 1, 3, 5, and 8% (wt/vol) in evaluations of their effectiveness as residual screen treatments to retard or prevent entry of Culicoides mississippiensis Hoffman adults into screened areas. These insecticides were evaluated on the basis of knockdown capability and the effect of weathering on their residual action. Propoxur at 8% was the most effective, with 73 to 92% quick (30 min) knockdown for 35 days and 97 to 100% overall mortality. Chlorpyrifos (8%) gave 97 to 100% overall mortality for 35 days but was inadequate in terms of quick knockdown. Malathion (8%) was effective only 14 days, and fenthion was ineffective at any of the concentrations tested.