First report of Oidium piperis on Piper aduncum in Brazil

Piper aduncum (local name ‘caapeba’), family Piperaceae, is native to Brazil. Widespread as an understory forest plant, it commonly grows next to roads and in banana plantations (Fig.1). Lorenzi (2000) notes P. aduncum as a weed, although it is also widely used in folk medicine in Brazil and elsewhere. In August 2004, P. aduncum plants attacked by a powdery mildew were identified besides Graciosa road, in the state of Paraná that passes through Atlantic tropical rainforest (the exact location was 25º 21’ 55" S and 48º 52’ 29" W).

Foliar lesions were yellowish with indistinct margins and had a whitish, powdery cover of fungal structures on the lower surface. The superficial mycelium was loose, branched, septate, hyaline, 5–9 µm diameter; appressoria indistinct to slightly nipple-shaped; conidiophores erect, cylindrical, 60 – 125 x 9 – 13 µm, 1-3 septate; conidia in long chains (2-8 conidia), ellipsoid-doliiform, 20 – 37 x 14 – 17 mm, hyaline, smooth, without fibrosin bodies (Fig. 2).

Based on these characteristics the fungus was identified as Oidium piperis. A specimen was deposited in the herbarium of the Universidade Federal de Viçosa (VIC 27825). The description of O. piperis provided in Braun (1987) states that conidia of this fungus are 20–74 x 6–23 µm (mostly 34–47 x 13–20 µm). Although our specimen had smaller conidia it was otherwise identical to Braun’s description. Previously reported only in India on Piper betle (Uppal et al., 1946) and in Denmark on Peperomia verticillata (Anon., 1981), there is no previous record of this fungus occurring in Brazil. This new finding suggests a much wider distribution and perhaps a more common occurrence than previously thought. Only minor was observed damage on isolated plants and the threat to medicinal use of P. aduncum appears small.