Disease Note.

Powdery Mildew of Potato Caused by Erysiphe cichoracearum in Brazil. L S. Boiteux, CNPH/EMBRAPA, C.P. 0218, 70359-970 Brasilia-DF, Brazil. Plant Dis. 78:830. Accepted for publication 24 March 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0830B.

Powdery mildew was observed on potato (Solanum tuberosum L.) 'Achat' plants growing in seed potato production greenhouses in Brasilia, Federal District, Brazil. Symptoms were characterized by an extensive growth of white, external (superficial) mycelium-producing colonies on both abaxial and adaxial leaflet surfaces. Bright yellow spots were observed on the opposite sides of each colony. Conidiophores formed cylindrical-ovoid conidia in long, terminal chains. Well-developed fibrosin bodies were not observed in the conidiophores and conidia. On the basis of morphological characteristics of the conidial stage, the fungus was identified as Erysiphe cichoracearum DC. ex Merat. (2). The perithecial (perfect) state was not oberved. All three monosporic isolates of E. chichoracearum obtained from potato were pathogenic to tomato {Lycopersicon esculentum Mill.) 'Rutgers' but not to squash {Cucurbita pepo L. var. melopepo (L.) Alef.) 'Caserta' or melon {Cucumis melo L.) 'Amarelo Valenciano', two previously reported hosts of this fungus (1,2). These data are suggestive of physiological specialization of £. chichoracearum in our area. This is the first report of E. chichora cearum causing potato powdery mildew in Brazil.