Larvicidal and repellent actions of Dalbergia sissoo Roxb. (F-Leguminosae)oil against mosquitoes

Studies were carried out to evaluate the larvicidal, growth inhibitor and r epellent actions of D. sissoo oil against Anopheles stephensi, Aedes aegypt i and Culex quinquefasciatus under laboratory conditions. Pure oil was appl ied at 0.4-5 ml/m(2) on a water surface. This showed that larvicidal activi ty was directly proportional to dosages. One hundred percent mortality of C k. quinquefasciatus immatures was observed within 24 h at 4 ml/m(2), follow ed by Ae. aegypti (90%) and An. stephensi (60%), and pupation was totally i nhibited. Adults which emerged from exposure to a sublethal dosage (2 ml/m( 2)) either did not lay eggs (Ae. aegypti) or hatch (Cx. quinquefasciatus an d An. stephensi). The oil also showed strong repellent action when 1 ml oil was applied on exposed parts of human volunteers. They were protected from mosquito bites for 8-11 h. The protection (91.6 +/- 2%) obtained with siss oo oil was comparable to that with commercial Mylol oil (93.8 +/- 1.2%) con sisting of di-butyl and dimethyl phthalates. (C) 2000 Elsevier Science Ltd. All rights reserved.