Symptoms: Lesions on foliage are elliptical or diamond shaped, approximately 2.5-3.5 × 1.5-2.5 mm. Lesion centers are grey and water soaked when fresh but turn brown on drying. Lesions are often surrounded by a chlorotic halo, which turns necrotic, giving the appearance of concentric rings.
Pathogen and disease characteristics: Asexual conidia are pyriform, hyaline, mostly three celled with a small appendage on the base cell. Conidia measure approximately 17.5-30.8 × 5.9-8.8 µm. (Mehta et al. 1953). Germination, appresoria formation, and invasion of host cells are greatest at 25 °C (Yadava and Agnihotri 1980).
Host range: Pearl millet, napiergrass (Pennisetum purpureum) (Buckley and Allen 1951).
Geographic distribution: India, Singapore (on napiergrass, Buckley and Allen 1951), United States.
Nomenclature discrepancies: Synonyms: Piricularia spp. (Mehta et al. 1953), P. grisea (Wells et al. 1969), Pyricularia penniseti (Prasda and Goyal 1970, Singh and Pavgi 1974), P. setariae (Rachie and Majmudar 1980).
Alternative names for the disease: Blast (Buckley and Allen 1951), brown leaf spot (Singh and Pavgi 1974), leaf blast (Rachie and Majmudar 1980), leaf spot disease (Mehta et al. 1953, Prasda and Goyal 1970,), piricularia leaf spot (Wells et al. 1969).
Seed transmission: Ahmed and Reddy (1993) have suggested that seed infection occurs. However, note that in the "Head Mold" section, isolation of P. grisea from seed has never been reported by other researchers (table 4). Transmission to seedlings has not been demonstrated.
Primary citations: As indicated above.
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Original posting: June 5, 1999.