Phyllachora Leaf Spot
Phyllachora penniseti Syd.
Symptoms: Leaves can be covered with numerous small, elongate, dark or black pustules that are 2-3 mm long when isolated but become confluent in mass. Both surfaces of the leaves can be affected. Symptoms usually develop after most vegetative growth has occurred or during grain fill.
Pathogen and disease characteristics: Pseudopycnidia develop in the stroma under the epidermis. Elliptical, cylindrical, unicellular, hyaline conidia measure 10-15 × 2.5-3 µm in diameter.
Nomenclature discrepancies:Synonyms or similar pathogens: Described as anamorphic Placosphaeria sp. in Saccas (1954) and Jouan and Delassus (1971). Leptosphaeria penniseti was isolated from napiergrass in Uganda was associated with Phyllachora and Stagonospora (Moreau 1949). Saccas (1954) indicates asci and ascospore dimensions of L. penniseti were consistent with Phyllachorapenniseti, although dimensions of L. penniseti differ from P. penniseti in Moreau (1949).
Alternative disease name: Tar spot.
Seed transmission: Not demonstrated to be transmitted by seed.
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Original posting: June 5, 1999.