An antimicrobial activity of tea polyphenols (catechins) against some plant pathogenic bacteria and fungi was tested. (-)Epicatechin gallate and(-)epigallocatechin gallate showed considerably a high inhibitory effect against Pseudomonas syringae pv. lachrymans, P. solanacearum, Xanthomonas campestris pv. citri and X. campestris pv. vesicatoria. (-)Epigallocatechin also showed and moderate growth inhibitory effect against X. campestris pv. citri and X. campestris pv. vesicatoria. On the other

more »

... d, methylated (-)epigallocatechin gallate had no inhibitory activity against these bacteria, but it specifically inhibited the growth of Pyricularia oryzae. The inoculation tests proved that crude catechins effectively prevented development of bacterial leaf spot of tomato caused by X. campestris pv. vesicatoria and citrus canker of Natsudaidai caused by X. campestris pv. citri. The effectiveness of crude catechins was about the same degree as that of a wettable copper compound (DOITSU BORUDOU-A). These results suggest that tea catechins may be useful to prevent occurrence of some bacterial plant diseases.