PURPOSE: To provide the subject composition containing a tannin-containing component and an organic acid, having high safety to human body, free from destructive effect on ecosystem and exhibiting high algicidal activity against microalgae such as pond scum. diatoms. green algae or blue-green algae.
CONSTITUTION: The objective algicide composition contains (A) a tannin- containing component and (B) an organic acid (e.g. glycolic acid, lactic acid, citric acid or ascorbic acid) and is formed in the form of solution, paste, powder, block, etc. The component A is e.g. raw or dried plant containing tannin (e.g. Geranium thunbergii, Uncaria gambir, miracle fruit, Eckloris bicyclis or gall of Rhus chinensis), extract of the plant with water, methanol, etc., or a fraction of the extract having high tannin content. The composition is applied, in the case of a closed system such as a pisciculture pond, at a rate to give a concentration of the component A of 0.5-50ppm as an extract in water and the amount of the component B in water is adjusted to 0.5-2 times weight of the component A.
EHATA SHINYA
ARAKI KEIKO
