Abstract: In order to screen out plant extracts with better antibacterial activity against anthracnose in Xihu Longjing tea producing area, the pathogens of tea anthracnose in this region were isolated and identified, and the inhibition activities of 12 plant extracts on the identified pathogen were determined using mycelial growth rate method. Concentration gradient test was further used to determine the antibacterial virulence of the top 3 plant extracts. The results show that Colletotrichum camelliae was the major pathogenic strain in the study region. At the concentration of 200 mg·L^-1, the antifungal activities of vitriol, oregano essential oil and perillal aldehyde were better, and their inhibition rates on the growth of anthrax were all above 68%, and their effective medium concentrations (EC₅₀) were 71.459, 77.155 mg·L^-1 and 110.753 mg·L^-1, respectively. Microscopic observation shows that the mycelium morphology of C. camelliae had obvious changes in the medium when supplemented with above plant extracts, showing deformation, distortion, shrinkage and shriveled. These results indicate that carvacrol, oregano essential oil and perill aldehyde have strong antibacterial activities against C. camelliae and possess potential for development as plant-derived fungicides.

Key words: tea plant, anthracnose, plant extract, antifungal activity, toxicity determination