First record of Erysiphe elevata on Catalpa bignonioides in the UK

Abstract

In 2002, a powdery mildew caused extensive patches of fine white bloom on the upper surfaces of leaves of a mature Indian bean tree ( Catalpa bignonioides ) in the Royal Horticultural Society's Garden, Wisley. In the absence of chasmothecia (ascomata), the assumed pathogen was Erysiphe catalpae , already known in Britain. However, in October 2003, abundant chasmothecia appeared with branched Microsphaera -like appendages, unlike the simple ones of E. catalpae . It conformed to E. elevata (syn. Microsphaera elevata ), previously only known in North America (Braun, 1984), but now reported in Hungary (Vajna et al ., 2004). The appressoria were mostly single and conspicuously lobed, some being paired, simple and kidney-shaped. Somewhat flexuous foot cells, 18-34 × 5-9 µ m, bore one to two other cells, 12-22 × 5-10 µ m. Cylindrical to elliptical conidia, 21-32 (43) × 9-16 (18) µ m (smaller than E. catalpae ), matured singly, being typical of Oidium subgen. Pseudoidium , the anamorph of Erysiphe. Scattered or grouped chasmothecia, diameter 95-132 µ m, bore four to eight (rarely one) equatorial appendages, 360-700 × 6 µ m (up to 9 µ m wide at the base), becoming flexuous in the upper half, but with bases stiff and straight, hyaline or brownish, thick-walled with a rough surface, occasionally with a septum close to the fruiting body. Their apices branched dichotomously, one to four times, with simple or knob-like tips when sparsely branched, but recurved when more complex, compact or widely forked. Chasmothecia contained three to eight short stalked asci, 45 -63 × 25 -39 µ m with four to six elliptical ascospores, 16 -20 × 8-11 µ m.

Distribution, Incidence and Severity of the Catalpa Powdery Mildew Caused by Erysiphe elevata in North-Eastern Romania

“…Worthy to mention, no powdery mildew species on Catalpa ovata were found in the hereby study. This taxon is included in the hosts list of E. elevata (Braun and Cook, 2012), but it is not mentioned in any published data from Europe, where the most frequent host plant is C. bignonioides (Ale-Agha et al, 2004;Cook et al, 2004;Milevoj, 2004;Cook et al, 2006;Pastirčáková et al, 2006;Stoykov, 2008;Heluta et al, 2009). Moreover, this powdery mildew was not detected on C. ovata in the UK (Cook et al, 2006).…”

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“…Useful comments of two anonymous reviewers were gratefully accepted in the final version and are greatly appreciated. Cook et al, 2004Cook et al, , 2006Millevoj, 2004;Vajna et al, 2004;Kiss, 2005;Pastirčáková et al, 2006;Heluta et al, 2009a), E. flexuosa (Peck) U. Braun & S.Takam.…”

First record of Phyllactinia moricola (Erysiphales, Ascomycota) on Morus alba in Europe

“…Braun & S.Takam. (Ale-Agha et al, 2004;Cook et al, 2004Cook et al, , 2006Millevoj, 2004;Vajna et al, 2004;Kiss, 2005;Pastirčáková et al, 2006;Heluta et al, 2009a), E. flexuosa (Peck) U. Braun & S.Takam.…”