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The knock down and insecticidal effects of the plants Tagetes minuta, Lippia javanica, Lantana camara, Tagetes erecta and Eucalyptus grandis were evaluated against Anopheles arabiensis mosquitoes in thatched round huts in Mumurwi village. Leaves from these plants were smouldered in order to provide mosquito repellent smoke. Complete knock down was provided 40 minutes after mosquitoes were exposed to smoke of T. erecta, 60 minutes to smoke of T. minuta and E. grandis and 120 minutes to smoke of L. javanica. Complete knock down of mosquitoes could not be provided by L. camara within the 140-minute exposure period. The KT50 (time required to knock down 50% of the mosquitoes) values were 24.985 minutes (T. minuta), 34.473 minutes (T. erecta), 59.119 minutes (L. javanica), 59.828 minutes (L. camara) and 25.245 minutes (E. grandis). The KT90 (time required to knock down 90% of the mosquitoes) values were 48.060 minutes (T. minuta), 50.169 minutes (T. erecta), 178.341 minutes (L. javanica), 140.220 minutes (L. camara) and 47.998 minutes (E. grandis). Mortality rates 24h after exposure were 40% (T. minuta), 100% (T. erecta), 75% (L. javanica), 90% (L. camara) and 100% (E. grandis). In conclusion, smoke from the plants T. erecta, T. minuta and E. grandis had very fast knock down rates with T. erecta, L. camara and E. grandis killing over 90% of the An. arabiensis mosquitoes. Plant smoke is important in mosquito control.