A cultivation method for white leaf tea has recently been developed, wherein the new shoots of tea plants (Camellia sinensis) undergo a 100% shading treatment with covering materials, such as cheesecloth. We examined the yield and leaf color of new shoots grown under strong shading treatment and assessed the quality of unrefined tea produced using new shoots grown under strong shading treatment using a sensory evaluation. The free amino acid content in the unrefined teas was also determined. The results from this study were used for the selection of suitable varieties from 12 tea cultivars varieties for white leaf tea production, which included recommended tea cultivars of Shizuoka Prefecture. We found that soil plant analysis development (SPAD) values for new leaves decreased after the strong shading treatment. Further, the leaf color of all the cultivars was white yellow. The SPAD values for the ‘Yamanoibuki,’ ‘Saemidori,’ ‘Meiryoku,’ ‘Fushun,’ and ‘Benifuuki’ cultivars were ≤ 10, which was lower than the SPAD value observed for the ‘Yabukita’ cultivar. The yield of the plucked new shoots of the first crop cultivated during the tea season was 137 - 317 kg/10a. The yield obtained from the ‘Sayamakaori,’ ‘Koushun,’ ‘Benifuuki,’ ‘Kanayamidori,’ ‘Okuhikari,’ and ‘Sawamizuka’ cultivars was equal to or higher than that of the ‘Yabukita’ cultivar. The total free amino acid content increased in all cultivars grown in the strong shading treatment. Particularly, the total free amino acid content of the ‘Saemidori’ and ‘Tsuyuhikari’ cultivars was 10% or higher. In the sensory evaluation of the unrefined teas, ‘Yamanoibuki’ was superior to ‘Yabukita,’ while ‘Saemidori’ and ‘Koushun’ were of similar quality to ‘Yabukita.’During the production of white leaf tea using the strong shading treatment, ‘Koushun,’ ‘Kanayamidori,’ and ‘Sawamizuka’ were suitable cultivars for high-yield production. Conversely, ‘Yamanoibuki,’ ‘Saemidori,’ and ‘Yabukita’ were suitable for production practices that emphasized quality and leaf color over yield. Furthermore, ‘Koushun’ was a suitable cultivar for producing white leaf tea based on the characteristic aroma and taste of the varieties, while ‘Tsuyuhikari’ was suitable for producing tea with high theanine content.

Exobasidium vexans causes blister blight, a serious disease on tea plants. Establishment of cultures on media is important to clarify its characteristics and to develop useful control methods. Other Exobasidium species, but not E. vexans, can grow on common fungal agar media. However, E. vexans can grow on home-made potato dextrose broth plus edible agar. Elemental analyses of edible agars suggested that more than 0.6 % calcium content in the agar was responsible for colony formation of E. vexans. Potato dextrose agar (PDA) amended with 100 mgL^-1 calcium (equivalent to 0.7 % calcium concentration and 15 gL^-1 of agar) achieved the successful culture of E. vexans. Among 7 calcium salts tested, calcium chloride, calcium chloride dihydrate, calcium carbonate, calcium hydrogen phosphate, calcium hydroxide, calcium nitrate tetrahydrate, and calcium sulfate dihydrate, 5 isolates of E. vexans were able to grow on PDA amended with calcium carbonate or calcium hydrogen phosphate, with calcium carbonate being most effective. The pH of the amended PDA ranged from 5.35 to 7.56. We successfully established and maintain E. vexans on media for the first time. Basidia and basidiospores were observed on the colony of E. vexans after 23 days of incubation. A commercial potato dextrose broth plus strip agar or commercial PDA amended with 100 mgL^-1 calcium (equivalent to 0.7 % calcium concentration and 15 gL^-1 of agar) can help to grow pure cultures of E. vexans.

An epizootic of entomophthoraceous fungi, Neozygites fresenii and Zoophthora radicans, in a population of Aphis aurantii in the tea fields of Iruma and Hidaka cities of Saitama Prefecture, Japan, is described. The aphid mortality ratio of each fungus was low in August 1981 and September 1983. The cadavers developing resting spores of N. fresenii were observed on the abaxial surface of tea leaves during early September 1983 and during mid-July 1989. The germinated resting spores were observed from mid-April to mid-May in 1991.

The leaves and shoots of three tea cultivars ‘Samidori, Asahi and Yabukita’, grown in natural shape bush formation, were measured. In ‘Samidori’, average leaf blade length and width were significantly shorter and average leaf blade area was significantly smaller compared to the other two cultivars and in ‘Asahi’, average leaf blade width was significantly longer compared to the other two cultivars. No significant difference was observed in the leaf shape index. The leaf area index, which was calculated using the estimation formula, was 5.8 in ‘Samidori’, 7.3 in ‘Asahi’ and 8.9 in ‘Yabukita’. The number of leaves and the number of shoots per unit area were both highest in ‘Samidori’ and both lowest in ‘Asahi’. Average shoot length was longest in ‘Yabukita’ and shortest in ‘Asahi’. The percentage of shoots below 30 cm was lowest in ‘Samidori’ and highest in ‘Asahi’.