Laboratory evaluation of methylated coconut oil as a larvicide for Anopheles farauti and Culex annulirostris.

The toxicity of methylated coconut oil (MCO) was compared with a commercially available oil larvicide (Golden Bear Oil GB-1111) in laboratory bioassays of 4th-stage larvae of Anopheles farauti Laveran and Culex annulirostris Skuse. Both larvicides were more toxic to Cx. annulirostris than to An. farauti and the LD50 (dose lethal to 50% of the test organisms) after 24 h exposure indicated that MCO was more toxic than GB-1111 for both An. farauti (LD50 = 8.6 microl versus 13.0 microl/156 cm2) and Cx. annulirostris (LD50 = 1.2 microl versus 3.6 microl/156 cm2). However, for LD95 GB-1111 was more toxic than MCO for both An. farauti (LD95 = 29 microl versus 48.0 microl/156 cm2) and Cx. annulirostris (LD95 = 7.2 microl versus 18.0 microl/156 cm2). Further study of MCO is warranted and may determine whether the addition of surfactant to MCO will lower the LD95. The possibility of community participation in the production and use of coconut products including MCO for malaria vector control is discussed.