LARVICIDAL POTENTIAL OF CRUDE EXTRACTS OF AZADIRACHTA INDICA (NEEM)
Duru, U.N, Orji J.C., Obi, R.K*
Department of Microbiology, Federal University of Technology, Owerri, P.M.B 1526, Owerri, Imo State, Nigeria.
ABSTRACT
A study was carried out to determine the larvicidal properties of bark,
leaf, and bark + leaf crude extracts of Azadirachta indica using 370
larval species of Anopheles mosquito obtained from stagnant and
swampy waters in and around Owerri. Forty larvae of the mosquito
were added to each treatment of the crude extracts stored in
concentrations of 25%, 50%, 75% and the mixtures maintained at
time schedules of 4h, 8h and 12h. Results obtained show that all the
larvae were susceptible but differed on times taken to achieve
maximum mortality. At 25% concentration, the highest and lowest
mortality rates of 22 (55%) and 3 (7.5%) were recorded after 12h and
4h exposures respectively with the bark extract. There was however
no significant difference in the mortality rates observed at this
concentration level of the different extracts (P < 0.05 = 10.260). At
50% concentration, the bark and leaf extracts recorded the highest
mortality rates of 20 (50%) after 8h exposure while the least of 3 (7.5%) came from leaf +
bark mixture after 12h. There was a significant difference in the mortality rates at this
concentration level of the different extracts (P < 0.05 = 11.444). Finally at 75%
concentration, the leaf + bark mixture produced the highest and lowest mortality rates of 26
(65%) and 3 (7.5%) at 8h and 12h respectively. There was no significant difference in the
mortality rates at 75% concentration of the different extracts (P < 0.05 = 5.443). Similarly,
results of the study carried out to determine the phytochemical properties of the extracts
revealed that out of the six properties tested for, only alkaloid was absent, while the remaining five were present, in both. This method of mosquito control is cheap and easy to
practice and could be adopted to halt further development of the mosquitoes into the adult,
which has become resistant to a large number of commercially available conventional
insecticides.
Keywords: Larvicidal, insecticide, Anopheles mosquito, larvae, Azdirachta indica, phytochemical.
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