Miscanthus Blight, A New Foliar Disease of Ornamental Grasses and Sugarcane Incited byLeptosphaeriasp. and Its Anamorphic StateStagonosporasp.

Abstract

Leaf spot and leaf blight were observed on the ornamental grass Miscanthus sinensis during the late summer and fall of 1993, 1994, and 1995 in three counties in Maryland. Severe disease symptoms occurred on residential landscape plants, nursery container stock, and commercial plantings of Miscanthus sinensis, M. s. var. gracillimus, M. s. var. variegatus, and M. s. var. zebrinus. The disease is characterized by reddish brown spots to oval streaks on leaves and sheaths. Leaf margins, leaf tips, and older leaves become necrotic. Younger plants become completely necrotic. Pycnidia and conidia of a species of Stagonospora with a Leptosphaeria teleomorph were observed on naturally infected necrotic Miscanthus leaves. The fungus was readily isolated in pure culture from affected plant parts. The fungus is homothallic, and both the anamorphic and teleomorphic states were produced on inoculated Miscanthus and sugarcane foliage, and on autoclaved sugarcane leaves. The anamorph may be morphologically distinct from other Stagonospora pathogens described from sugarcane, but the teleomorph is similar to leptosphaeria taiwanensis (anamorph Stagonospora tainanensis), cause of sugarcane leaf blight. In growth chamber inoculations, conidia produced by the Miscanthus fungus and by S. tainanensis from sugarcane were highly virulent and caused similar blight symptoms on four Miscanthus varieties and six sugarcane clones. Sugarcane leaf blight is a serious disease in Taiwan but has not been reported from the United States. The name proposed for the new disease on Miscanthus is Miscanthus blight, caused by leptosphaeria sp. and its conidial state Stagonospora sp.