Zonate Leaf Spot
Gloeocercospora sorghi Bain & Edgerton
Symptoms: Foliar lesions appear as water-soaked spots that develop tan centers and dark brown borders and measure 3.5-5 × 2-3.5 mm. Spots enlarge, forming roughly semicircular blotches covering about half of the leaf width. Blotches are various shades of dark brown mottled with pale tan spots that may appear as concentric rings of alternating tan and brown.
Note that disease symptoms of zonate leaf spot illustrated in Williams et al. (1978) were later attributed to dactuliophora leaf spot (Tyagi 1985). Symptom expression of and differentiation between these two diseases need to be clarified.
Pathogen and disease characteristics: Conidia borne on short, erumpent stromata are attenuate-obclavate, hyaline, multiseptate, and approximately 74.5-2.2 µm. In moist weather, tiny, salmon-colored globules of conidial masses on the foliar lesions are visible with a hand lens.
Host range: Pearl millet, sorghum.
Nomenclature discrepancies: None.
Seed transmission: Very infrequently isolated from seed (Wilson et al. 1993). Transmission by seed has not been demonstrated.
Primary citation:Luttrell 1954.
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Original posting: June 5, 1999.