a1 International Centre of Insect Physiology and Ecology, P.O. Box 30772, Nairobi, Kenya
a2 London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
a3 AFRC Institute of Arable Crops Research, Rothamsted Experimental Station, Harpenden, Herts., AL5 2JQ, UK
The synthetic attractant pheromone 6-acetoxy-5-hexadecanolide in a formulation of 20 mg containing 5 mg of the active (−)-(5R,6S)-isomer in an effervescent tablet produced a high, positive overall response by gravid females of Culex quinquefasciatus Say when the mosquitoes were exposed to the pheromone in established breeding sites in western Kenya. Significantly more females (82%) oviposited around the pheromone source compared to a control. The activity of the pheromone persisted in the established breeding place for four days after application. The addition of the insect growth regulator S-31183 (2-[1-methyl-2-(4-phenoxyphenoxy)ethoxy]pyridine) to the formulation did not affect the activity of the pheromone. Newly-made breeding sites exposed domestically were not attractive initially for oviposition by gravid females but, after 18 days, they became more attractive. Trays treated with synthetic pheromone diverted females from similar unbaited trays exposed within 10 m. A sample of larvae taken from a site treated with pheromone and insect growth regulator showed 100% mortality by the pupal stage. Thus, the efficacy of the pheromone has been demonstrated for the first time in the field and the possibility of using this material in combination with a ‘safe’ insecticide confirmed.
(Received December 01 1987)
c1 Correspondence to: Dr B. R. Laurence, School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK.