Efficacy of Thai Herbal Extract for Growth Inhibition of Xanthomonas axonopodis pv. citri , the Bacterial Canker of Citrus

Abstract

The efficacy test of Thai herbal extract for growth inhibition of Xanthomonas axonopodis pv. citri, the causal agent of bacterial canker of citrus, was studied. The experiment was conducted by Paper disc diffusion method on double layer NGA. The 23 kinds of Thai herbal extracted by 95% ethyl alcohal at the concentration of 100,000 ppm were tested. Five kinds of those could inhibit the growth of bacteria on culture media and showed the typical inhibition zone. Those were guava leaf, beleric myrobalan fruit, pomegranate fruit peel, nut gall fruit and myrobalan wood fruit. But the other 18 kinds showed no inhibition zone. The 5 kinds of extract that showed high efficacy were diluted to 5 concentration lavels of 100,000, 50,000, 10,000, 5,000, and 1,000 ppm and tested by paper disc diffusion method again. It was founded that the guava leaf extract could inhibit the growth of bacteria at 50,000 ppm, the myrobalan wood fruit extract could inhibit the growth of bacteria at 10,000 ppm, the extract of beleric myrobalan fruit, nut gall fruit and pomegranate fruit peel could inhibit the growth of bacteria at all concentration levels started at 1,000 ppm.