Claviceps yanagawaensis TOGASHI distributes very commonly in the Zoysia-growing region of the northern range of Honshu and probably far to the southern, occurring at least in Nagano Prefecture. In certain range, 40% or more of the Zoysia spikes are attacked by the fungus, the ergot yield being estimated as 150 g to 400 g in 400 square meters.
In the northern districts, the blooming period of Zoysia japonica extends from the middle of June to the first 10 days of July, during which high moist weather continues for several days and air temperature mostly fluctuates between 15° and 20°C., the meteorological conditions are apparently quite favorable to the formation of sphaeridia and to the infection of the fungus.
The sclerotia mature at the end of September, showing the mean values of 6.35±0.05 mm in length, 0.81±0.003 mm in width, and 2.26±0.02 mg in weight. Generally, one sphaeridium is produced from one sclerotium with a variation of 1-7. The biometrical means of the sphaeridia, perithecia, asci, and ascospores are 1.08±0.01×1.22±0.01 mm, 244.9±1.8×130.6±1.4μ, 145.3±1.1×5.15±0.03μ, and 124.4±0.8×1.32±0.02μ, respectively.
The conidia are very variable in shape, showing ellipsoidal, ovoidal, spindle-shaped, etc., colorless, and measure 11.03±0.05×5.35±0.02μ.