Contact Toxicity of Cashew Nut Shell Liquid Extract on Adult <i>Bactrocera dorsalis</i> (Hendel)

This study investigated the contact toxicity of cashew nut shell liquid (CNSL) against fruit fly Bactrocera dorsalis (Hendel) using two solvents, hexane and dichloromethane. One ml of the prepared concentrations (0, 0.625, 1.25, 2.5, 5.0, 10.0 and 20.0 x 104 ppm) was applied to the filter paper lined in an 85 mm dia petri dish. Acetone alone was used as a control. Ten male adults B. dorsalis were released on each of the treated discs. Mortalities were recorded at 6, 12, and 24 hr after release. Of the two, the dichloromethane extract recorded the highest mortality 82% at the 20 x 104 ppm concentration after 24 hr of exposure. The probit values showed that dichloromethane extract was 1.42 times more lethal than hexane extract as indicated by its lower LC50 (4.66 x 104 ppm) value as opposed to LC50 (6.58 x 104 ppm) for hexane after 24 hr of exposure.