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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Assefa, Tigist

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Addis Ababa University


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.