Vol. 4, Issue 3, Part B (2017)

Author(s): Atallah F Mekhlif

Abstract: Screening of fourteen xerophyte plants as mosquito larvicides for 4^th instar Culex pipiens molestus. More effective with high toxicity nine species; Achelia fragrantissima [Af], Tanacetum cantolinoides [Tc] (Asteraceae), Cakile Arabica [Ca], Horwoodia dicksonia [Hd] (Brassicaceae), Astragalus annularis [Aa] (Fabaceae), Erodium glaucophyllum [Eg] (Geraniaceae), Resida muricata [Rm] (Residacea) and Fagonia indica [Fi] (Zygophyllaceae). Their Lc₅₀ and Lc₉₀ after 24 and 48 hrs were evaluated. Lc₅₀ values after 24 hrs gradually: 12.5, 40.5, 43.0, 70, 86, 103.5, 104, 105.5 and 135 ppm for Fa, Af, Aa, Eg, Ca, Tc, Hd, Rm and Ah respectively. For testing the plant extracts residual toxicity persistence, the test starts with potential concentration causing mortality 100% for the 4^th instar larvae, as following ; Fi 25. and Af 100 ppm, Aa, Eg, and Ca 150 ppm, Rm, Tc and Hd 200 ppm and for Ah 250 ppm. Ficum^®W was applied as positive control and standard insecticide positive control with 15 ppm and negative control. The extract toxicity declined significantly with plant extract species and its exposure time which becomes zero at day 9 for Rm, day 12 for Aa and Hd,and day 15 for Fi, Ca, Tc and Ah, while continues with 40 and 31.2% mortality at day 15 for Af, and Eg respectively, in comparison with 70.8% mortality for standard insecticide Ficum^®W at day 16. On the bases of this study, xerophytic plant could be considered with promising main botanical insecticidal resources which needed more investigation.

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