CONTACT TOXICITY OF PERMETHRIN-IMPREGNATED MILITARY UNIFORMS TO CULEX-PIPIENS (DIPTERA, CULICIDAE) AND PHLEBOTOMUS-PAPATASI (DIPTERA, PSYCHODIDAE) - EFFECTS OF LAUNDERING AND TIME OF EXPOSURE

The effects of laundering and time of exposure on the insecticidal act ivity of military uniform fabric impregnated with permethrin at 0.125 mg active ingredient (AI)/cm(2) are reported from susceptibility tests with laboratory-reared mosquitoes, Cuter pipiens, and sand flies, Phl ebotomus papa tasi. Knockdown/mortality resulting from exposure of gro ups of female insects for periods of 1, 3, 5, 7, and 10 min was record ed and compared among 5 different treatment/wash groups (untreated/unw ashed, treated/unwashed, treated/1-wash, treated/2-wash, treated/3-was h). Laundering was by machine washing with detergent and warm water fo llowed by hot-air machine drying. Post-exposure assessments at interva ls from 0 to 60 min and at 24 h showed that knockdown for each exposur e time and wash group was initially low but increased steadily during the first hour post-exposure. Sand flies were less sensitive than mosq uitoes to knockdown during the first 60 min after contact with treated /unwashed fabric; however, 24-h mortality rates for sand flies were hi gher as compared with mosquitoes. The permethrin remaining after a 3rd wash had little knockdown effect on mosquitoes but was toxic to sand flies at each of the 5 exposure times. Significant reductions in the k nockdown effectiveness of permethrin-treated fabric to mosquitoes and sand flies was associated with single and repeated washings of the fab ric.