Inhibitory Effects of Galla chinensis, Tannic Acid, and Gallic Acid on Saprolegnia parasitica

Abstract

The inhibitory effects of Galla chinensis and its two main ingredients, tannic acid and gallic acid, on Saprolegnia parasitica were examined, using the method of agar plate assay and liquid dilution assay. The results showed that all the three tested drugs had different degrees of inhibitory activity on mycelial growth and zoospore germination of Saprolegnia parasitica, with tannic acid showing the most significant inhibition. The mycelial growth of S. parasitica was completely inhibited by tannic acid at the concentration of more than 32 mg/L, and the germination rate of S. parasitica zoospores decreased by 66% at a concentration of 5 mg/L. Considering the low cost of tannic acid together with its inhibitory effect on S. parasitica, tannic acid showed the most significant potential in the prevention and control of fish saprolegniasis