Preliminary studies on the use of ultra-low-volume applications of malathion for control of Aedes simpsoni.

In view of the threat of additional yellow fever epidemics in East Africa and recent successes in the use of malathion applied by the ultra-low-volume technique against insect vectors, field trials were initiated in November 1968 to test the efficacy of this method against Aedes simpsoni. Results of these trials show that in areas where Musa ensetta is the principal breeding site, the application of 20.2 US fl oz/acre (1474 ml/ha) of malathion was capable of reducing vector populations 93%-100%. Comparable applications of 6 US fl oz/acre (438 ml/ha) reduced populations by 76% and 89%. Since this study did not conclusively demonstrate that the 6 US fl oz/acre dosage rate was sufficient to obtain maximum population reduction, further studies should be initiated to obtain information on the optimal dosage to be employed against this species.Under the conditions of these trials, the use of a light, single-engined aircraft equipped with a rotary atomizer spray system and capable of operation from improvised fields was shown to be feasible against this vector species. It was further demonstrated that the canopy formed by M. ensetta does not present an impossible barrier to the penetration of the spray droplets produced by the ULV application technique.Observations made on the application methodology and on the biology of A. simpsoni show the versatility of this species and the need for further studies on the integration of spray applications with the peak activity periods of the insect.