The efficacy of various pyrethroid insecticides for use on odour-baited targets to control tsetse

The efficacy of various pyrethroid insecticides for use on odour-baited tar gets to control tsetse was compared in Zimbabwe. Formulations were applied to cotton cloth and polyester net and, at various intervals, the materials were bioassayed by exposing fed female Glossina pallidipes (Austen) (Dipter a: Glossinidae) to cloth for 45 s or by inducing them to collide briefly wi th net. Trial formulations were compared with deltamethrin suspension conce ntrate (s.c.), the insecticide currently used in tsetse control operations in Zimbabwe. Applying 0.8% suspension of alphacypermethrin to cloth or net produced high mortalities for 9 months which was similar in performance to 0.4% suspension of deltamethrin s.c. Deltamethrin s.c, and beta-cyfluthrin s.c. applied to cloth as 0.1% suspensions were equally effective, producing high mortalities for 2 months during the wet season, and 0.8% suspension o f beta-cyfluthrin was effective for 12 months. Suspensions of 0.1% lambdacy halothrin capsule suspension or 0.1% lambdacyhalothrin wettable powder were significantly less effective than 0.1% deltamethrin s.c. Chemical analyses showed that increasing the concentration of insecticide applied to materia l increased the initial amount of insecticide on the material and decreased the subsequent rate of loss; 0.1% suspension of beta-cyfluthrin s.c. appli ed to cloth produced an initial concentration of approximate to 280 mg/m(2) which declined by 94% in 12 months whereas 0.8% suspension showed no signi ficant decrease in concentration (mean = 1304 mg/m(2)) over the same period . For controlling tsetse by means of pyrethroid-treated targets, it is sugg ested that beta-cyfluthrin s.c. is as effective as deltamethrin s.c. but th at alphacypermethrin s.c. should be used at twice the concentration of delt amethrin s.c. to obtain the same performance.