Evaluation of the larvicidal effects of Annona squamosa and Tagetes minuta essential oils and crude extracts against Anopheles mosquito larvae under laboratory and semi field conditions
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Date
2011-06
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Addis Ababa University
Abstract
The larvicidal activity of solvent extracts of Annona squamosa, Tagetes minuta and essential oils of both
plants were evaluated against laboratory colonies and field collected larvae of Anopheles. Shade dried and
grounded seed from A. squamosa and floral part of T. minuta were sequentially extracted with acetone,
hexane, ethanol and distilled water. A series of concentration of the extracts ranging from 6.25ppm to
100ppm were tested against 3rd-4th instar larvae of An. arabiensis and their percentage mortalities were
recorded. The acetone and hexane extracted A. squamosa showed very high larvicidal activity, where
96% and 98% mortality were recorded respectively in the laboratory and 90% and 87.5% mortality
respectively in semi- field at a concentration of 100ppm. In the laboratory, the LC50 values of different
solvent extracts tested ranged from 13.3ppm to 574.9ppm against An. arabiensis. Similarly, the LC90
values ranged from 48.35ppm to 916.1ppm. However, acetone and hexane extracted A. squamosa with
LC50 of 13.3ppm; 23.3ppm and LC90 59.9ppm, 48ppm respectively showed strong larvicidal activity
against An. arabiensis under laboratory condition after 24hrs exposure. On the other hand, the field LC50
and LC90 values of tested solvent extracted plants ranged from 28.0ppm to 410.2ppm and 82.45ppm to
656.1ppm, respectively and Acetone and Hexane extracted A. squamosa was the most effective with LC50
28.0ppm;32ppm and LC90 84ppm;82ppm, respectively. Also A. squamosa and T. minutia of essential oils
in the present study exhibited a larvicidal activity against 3rd - 4th instar larvae of An. arabiensis. Annona
squamosa essential oils exhibited 99% and 71% larval mortality both in the laboratory and semi-field
conditions respectively at the concentration of 66.67ppm than T. minuta essential oils. Moreover, of the
two tested essential oils, A. squamosa oil induced highest larvicidal effects both in the laboratory and in
field with LC50 41.5ppm; 31.5ppm and LC90 79.2ppm; 32.9ppm, respectively. The results suggest that the
investigated plant extracts are promising as larvicides against An. arabiensis and could be useful in the
search for new and biodegradable plant derived larvicide’s products.
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Biology