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Algicidal properties of Acacia nilotica
Aquatic Botany, 23 (1986) 389--390
389
Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
Short Communication
ALGICIDAL P R O P E R T I E S O F ACACIA NILOTICA
SAAD MOHAMED HUSSEIN AYOUB
Department of Phytochemistry, Medicinal and Aromatic Herbs Research Unit, The National Council for Research, P.O. Box 2404, Khartoum (Sudan) (Accepted for publication 14 October 1985)
ABSTRACT Hussein Ayoub, S.M., 1986. Algicidal properties of Acacia nilotica. Aquat. Bot., 23: 389--390. The algicidal activity of aqeuous extracts of the pods of Acacia nilotica (L.) Willd, ex Deh was tested in artificial ponds. Algae belonging to the genera Rivularia, Oscillatoria, Spirulina, Chroococcus, Microcystis (Cyanophyceae), Pediastrum, Coelastrum (Chlorophyceae), Spirogyra, Cosmarium, Closterium (Conjugophyceae), Euglena (Euglenophyceae) and CycloteUa (Bacillariophyceae) were successfully controlled with this extract.
Mass increase of algae, particularly in inland waters including reservoirs and irrigation canals, creates serious problems both in developing a n d in agrarian countries. Floating weeds and algae lead to clogged pipe lines, blocked sluices and choked filter pumps, Transport and fishing b e c o m e difficult or impossible, and snails and disease-carrying insects find shelter and protection from their natural enemies. Mechanical control o f algae and aquatic weeds is laborious and c o s t l y . Biological control is considered to be the most suitable control m e t h o d , particularly as chemical agents may have m a n y undesireable side effects. The use of plant-derived algicides in a country such as the Sudan, w h i c h has great extremes of meteorological, climatic and topographical features, a n d a rich flora, is feasible and m a y be a suitable m e t h o d of control. The p o d s of Acacia nilotica (L.) Willd. ex Del. (Mirnosaceae), a c o m m o n tree t h r o u g h o u t the Sudan, were f o u n d to possess algicidal activity against several species. The activity of aqueous extracts of the pods against algae was t e s t e d in artificial ponds, each containing ca. 6 m ~ of water. After the f o r m a t i o n of algal populations in the ponds, the aqueous extract of the pods was a d d e d at various concentrations (20, 40, 60 . . . . , 180 or 200 p p m ) and the time elapsing before the disappearance of the algal population was d e t e r m i n e d . Addition of 20--40 ppm of the extract caused c o m p l e t e disappearance of the algae within 4 days; concentrations of 60--100 p p m caused the same in 3 days; concentrations of 120--200 p p m had the same result in 2 days. Tests with each concentration were duplicated. It was observed that during 0304-3770/86/$03.50
© 1986 ElJevier Science Publishers B.V.
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the test period, the floating masses of algae normally changed colour from blue--green to pale green or brownish, disintegrated and finally s a n k . As the pods are known to have a high content of tannins (18--23%) (Dalziel, 1937; Watt and Breyer-Brandwijk, 1962), approximately 10% solution was prepared from the aqueous extract of the pods and treated with hide powder (Anon., 1928). The tannins become bound to the hide powder. The tannin-free solution was filtered, concentrated in vacuo and freeze-dried. The same concentrations of the tannin-free extract of Acacia pods were added to new algal populations, but appeared to have no algicidal activity. The algae effectively controlled with the extract of the pods of Acacia nilotica belonged to the genera: Rivularia; Oscillatoria; Spirulina; Chroococcus; Microcystis ( Cyanophyceae); Pediastrurn ; Coelastrum ( Chlorophyceae ); Spirogyra; Cosmarium; Closterium (Conjugophyceae); Euglena (Euglenophyceae) and Cyclotella (Bacillariophyceae). ACKNOWLEDGEMENTS
The author is grateful to Mr. Amin Michael (Khartoum International Fair) and Professor A.G.A. Kaxim (University of Khartoum) for help and algal identification.
REFERENCES
Anonymous, 1928. Allen's Commercial Organic Analysis, Vol. V. Churchill, London, pp. 126. Dalziel, J.M., 1937. The Useful Plants of West Tropical Africa. The Crown Agencies for the Colonies, London. Watt, J.M. and Breyer-Brandwijk, M.G., 1962. In: E.R.S. Livingstone (Editor), The Medicinal and Poisonous Plants of Southern and Eastern Africa. E. and S. Livingstone, Edinurgh, pp. 536.
389
Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
Short Communication
ALGICIDAL P R O P E R T I E S O F ACACIA NILOTICA
SAAD MOHAMED HUSSEIN AYOUB
Department of Phytochemistry, Medicinal and Aromatic Herbs Research Unit, The National Council for Research, P.O. Box 2404, Khartoum (Sudan) (Accepted for publication 14 October 1985)
ABSTRACT Hussein Ayoub, S.M., 1986. Algicidal properties of Acacia nilotica. Aquat. Bot., 23: 389--390. The algicidal activity of aqeuous extracts of the pods of Acacia nilotica (L.) Willd, ex Deh was tested in artificial ponds. Algae belonging to the genera Rivularia, Oscillatoria, Spirulina, Chroococcus, Microcystis (Cyanophyceae), Pediastrum, Coelastrum (Chlorophyceae), Spirogyra, Cosmarium, Closterium (Conjugophyceae), Euglena (Euglenophyceae) and CycloteUa (Bacillariophyceae) were successfully controlled with this extract.
Mass increase of algae, particularly in inland waters including reservoirs and irrigation canals, creates serious problems both in developing a n d in agrarian countries. Floating weeds and algae lead to clogged pipe lines, blocked sluices and choked filter pumps, Transport and fishing b e c o m e difficult or impossible, and snails and disease-carrying insects find shelter and protection from their natural enemies. Mechanical control o f algae and aquatic weeds is laborious and c o s t l y . Biological control is considered to be the most suitable control m e t h o d , particularly as chemical agents may have m a n y undesireable side effects. The use of plant-derived algicides in a country such as the Sudan, w h i c h has great extremes of meteorological, climatic and topographical features, a n d a rich flora, is feasible and m a y be a suitable m e t h o d of control. The p o d s of Acacia nilotica (L.) Willd. ex Del. (Mirnosaceae), a c o m m o n tree t h r o u g h o u t the Sudan, were f o u n d to possess algicidal activity against several species. The activity of aqueous extracts of the pods against algae was t e s t e d in artificial ponds, each containing ca. 6 m ~ of water. After the f o r m a t i o n of algal populations in the ponds, the aqueous extract of the pods was a d d e d at various concentrations (20, 40, 60 . . . . , 180 or 200 p p m ) and the time elapsing before the disappearance of the algal population was d e t e r m i n e d . Addition of 20--40 ppm of the extract caused c o m p l e t e disappearance of the algae within 4 days; concentrations of 60--100 p p m caused the same in 3 days; concentrations of 120--200 p p m had the same result in 2 days. Tests with each concentration were duplicated. It was observed that during 0304-3770/86/$03.50
© 1986 ElJevier Science Publishers B.V.
390
the test period, the floating masses of algae normally changed colour from blue--green to pale green or brownish, disintegrated and finally s a n k . As the pods are known to have a high content of tannins (18--23%) (Dalziel, 1937; Watt and Breyer-Brandwijk, 1962), approximately 10% solution was prepared from the aqueous extract of the pods and treated with hide powder (Anon., 1928). The tannins become bound to the hide powder. The tannin-free solution was filtered, concentrated in vacuo and freeze-dried. The same concentrations of the tannin-free extract of Acacia pods were added to new algal populations, but appeared to have no algicidal activity. The algae effectively controlled with the extract of the pods of Acacia nilotica belonged to the genera: Rivularia; Oscillatoria; Spirulina; Chroococcus; Microcystis ( Cyanophyceae); Pediastrurn ; Coelastrum ( Chlorophyceae ); Spirogyra; Cosmarium; Closterium (Conjugophyceae); Euglena (Euglenophyceae) and Cyclotella (Bacillariophyceae). ACKNOWLEDGEMENTS
The author is grateful to Mr. Amin Michael (Khartoum International Fair) and Professor A.G.A. Kaxim (University of Khartoum) for help and algal identification.
REFERENCES
Anonymous, 1928. Allen's Commercial Organic Analysis, Vol. V. Churchill, London, pp. 126. Dalziel, J.M., 1937. The Useful Plants of West Tropical Africa. The Crown Agencies for the Colonies, London. Watt, J.M. and Breyer-Brandwijk, M.G., 1962. In: E.R.S. Livingstone (Editor), The Medicinal and Poisonous Plants of Southern and Eastern Africa. E. and S. Livingstone, Edinurgh, pp. 536.