Scab of Tea (Thea sinensis) Caused by Cladosporium herbarum in Korea

In 2001, a black scab disease was observed in tea plant (Thea sinensis) cultivated in the hillsides of Hwngaemyon and Hadong-gun, Gyeongnam province, Korea. The disease symptoms initially appeared on leaves, green twigs and stems, showing small dark brown spots on the infected areas, which gradually expanded. A fungus was isolated from diseased leaves and green twigs. It grew readily on potato dextrose agar, forming dark green to dark gray colonies. The optimum temperature for mycelial growth was about 20$^{\circ}C$. The diameter of growing hyphae was 3.5-5.8 $\mu\textrm{m}$. Conidia were ellipsoidal, ovoid or subspherical, and mostly one-celled but occasionally septate. The size of one-celled and septate conidia were 3.7-12.4${\times}$3.4-5.2 $\mu\textrm{m}$ and 9.3-18.7${\times}$3.8-7.2 $\mu\textrm{m}$, respectively. Conidia were formed in long branched chains on the erected conidiophores, which were dark brown in color and 28.9-218.3${\times}$3.0-6.1 $\mu\textrm{m}$ in length. The fungus was identified as Cladosporium herbarum on the basis of its morphological characteristics. The black scab disease occurring in tea caused by Cladosporium herbarum has not been previously reported in Korea.