Trials of residual sprays of Mobam and carbaryl against mosquitoes in verandah-trap huts at Taveta, Kenya

Abstract

Two carbamate insecticides, Mobam (4-benzothienyl methylcarbamate) and carbaryl, were tested at dosages of 2 g/m2 active ingredient in grass-roofed verandah-trap huts at Taveta, Kenya, in 1967 and 1968, respectively. In Mobamtreated huts, overall mortalities were over 70% for 20 weeks in Anopheles gambiae Giles and A. funestus Giles, and for 12 weeks in Culex pipiens fatigans Wied. In the carboryl-treated huts overall mortalities were over 70% for 12 weeks in A. funestus, but in A. gambiae and C.p. fatigans never exceeded 64% and 33%, respectively. Neither compound had a deterrent effect on A. gambiae, which entered the treated huts in more than the expected numbers. Mobam did not appear to be repellent; and carbaryl was only slightly so. Egress of blood-fed A. gambiae increased after treatment but most of the mosquitoes died after reaching the verandah traps. There were slightly more unfed A. gambiae in the treated huts than in the control hut but there were never more than 35% unfed.