First report of powdery mildew caused by Podosphaera pannosa on a new host - sour cherry - in Hungary

In July of 2002, typical symptoms of powdery mildew were observed on leaves of cultivars Pándy 279 and Érdi Bőtermő of 5-year-old sour cherry trees (Prunus cerasus) in the orchard of the Research Institute for Fruit Growing and Ornamentals, close to the city Érd. White, epiphytic mycelia and conidia were present on leaves; forming thin, irregular colonies on either sides of leaves (Fig. 1 & 2a). Later, in September, white cottonlike growth developed in the infected area of many leaves (Fig. 2b). Severe infection resulted in leaf curling and blistering (Fig. 1). At the end of October 100% of leaves were severely infected. Cleistothecia were found beginning in mid-October, immersed in cottonlike dense mycelial layer (Fig. 3a).

Persistent secondary mycelium was dense and pannose; conidiophores were erect with cylindrical foot cells; conidia developed in chains, were ellipsoid-ovoid, 14.3 x 29.0 µm (Fig. 3c); cleistothecia were immersed in mycelium, 80 - 120 µm diam., cells were irregularly polygonal, rounded, 10 - 20 µm in diameter; appendages developed in the lower half, were mycelium-like, short, often rudimentary, hyaline, later turned yellowish to brown, 3.8 - 4.0 µm thin; asci were ellipsoid-ovoid, 68 - 80 x 79 - 89 µm, 8-spored (Fig. 3b); ascospores were ellipsoid-ovoid, 12.5 x 20.0 µm.

The morphology of this powdery mildew fungus conformed to Podosphaera pannosa (syn. Sphaerotheca pannosa) (Braun 1995; Braun & Takmatsu, 2000). The specimens are preserved in the Herbarium of the first author (Plant Protection Institute, Budapest). Severe infection of sour cherry cultivars might be caused by the dense planting, high humidity and drastic pruning of trees in 2001, resulted in the development of water sprouts. According to our knowledge, this is the first report of Podosphaera pannosa on sour cherry in Hungary and elsewhere.