TOXICITY EVALUATION OF ETHANOLIC AND AQUEOUS EXTRACT OF AZADIRACHTA INDICA AND MOMORDICA CHARANTIA ON SPIRALING WHITEFLY, ALEURODICUS DISPERSUS (HOMOPTERA: ALEYRODIDAE)

Abstract

Spiraling whitefly, Aleurodicus dispersus Russell (Homoptera: Aleyrodidae) poses threat to many fruit and ornamental crops. Fresh leaves extracts of Azadirachta indica (Meliaceae: Sapindales) and Momordica charantia L. (Cucurbitales: cucurbitaceae) obtained with ethanol and water as solvents were evaluated in the laboratory for their insecticidal effect on adults of the spiraling whitefly at 350, 400, 450, 500 and 550 mg/L. The extracts were applied onto guava leaves to observed the mortality of adults by topical and residual spray methods, and later their effectiveness and to obtain the LT50. Ethanolic extracts of neem were effective and caused 100% mortalities within the16 and 20 hours by topical and residual spray methods. On the other hands, ethanolic extracts sprayed with only water killed 100% of spiraling whitefly within the 28 hours after treatment by topical and residual methods. The ethanol extracts at the two highest concentrations (500 and 550 mg/L) showed highest mortality against spiraling whitefly. In bitter gourd extract, ethanolic extracts were effective and caused 100% mortalities within the 20 and 28 hours by topical and residual spray methods. On the other hands, ethanolic extracts sprayed with only water killed 100% of spiraling whitefly within the 28 hours after treatment by topical and residual methods. The ethanol extracts at the two highest concentrations (500 and 550 mg/L) showed highest mortality against spiraling whitefly. The LT50 of the ethanol extracts, calculated through Probit analysis, was lower than the LT50 achieved by the aqueous extracts in dose 500 and 550 mg/L. Additionally, the repellency effect of both extracts of neem on adults was determined. The ethanolic extracts showed highest mean repellency rate (93.33% and 95.55%) at the dose of 500 and 550 mg/L, respectively and it belongs to the repellency class V. Therefore, the ethanol extracts caused greater mortality than the water extracts at similar concentrations.