Symptoms: Symptoms begin on the upper leaf surface as pinpoint isolated brown lesions. As the lesions increase in size, they become brownish at the edge and dirty white or straw colored toward the center. In wet weather, irregular water-soaked areas develop around the spots and turn necrotic. Well-developed lesions have no definite shape or are roughly oval or semicircular, zonate with kidney-shaped patches of necrotic tissue and brown or yellow tissue in between. Black sclerotia develop in upper surface of necrotic tissue.
Pathogen and disease characteristics: Tan aerial mycelium without sclerotia develops on potato dextrose agar. On the host, the white mycelium is appressed to the cuticle on the lower leaf surfaces. Obclavate-ellipsoid to pyriform, brown sclerotia develop on erumpent, cup-shaped sclerotiophores. Sclerotia germinate by producing germ tubes over the entire surface after 4 to 8 hours.
Host range: Pearl millet.
Nomenclature discrepancies: Disease symptoms illustrated in Williams et al. (1978) and attributed to zonate leaf spot (Gloeocercospora sorghi) are probably those of dactuliophora leaf spot.
Seed transmission: Not known to be transmitted by seed.
Primary citation:Tyagi 1985.
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Original posting: June 5, 1999.