First Report of Powdery Mildew of Tecoma capensis Caused by Erysiphe peruviana in North America

Tecoma capensis (Thunb.) Lindl. (Bignoniaceae, common name: Cape honeysuckle), native to southern Africa, is grown as an ornamental plant in warm regions of the USA. The powdery mildew reported previously from T. capensis in North America was an undetermined Oidium species in Florida (2). The present report documents the occurrence of the powdery mildew fungus Erysiphe peruviana (Syd.) U. Braun & S. Takam. on T. capensis in Arizona. Powdery mildew was observed on a specimen plant growing in a private garden in Yuma, Yuma Co., AZ, in April of 2008 and 2009. The disease was apparent until about mid-May. Disease signs included effuse, whitish colonies on adaxial leaf surfaces (Fig. 1). Infections occurred on foliage receiving little or no direct sunlight, and no significant damage occurred. Infected leaflets and leaves eventually abscised. No new infections were observed after early May. The fungus formed ectophytic hyphae with lobed appressoria (Fig. 2); cylindrical conidiophore foot cells (Fig. 3) measuring (15.5-) 16-19(-20.5) × 5.57.5(-9.5) μm; and ovoid to cylindrical conidia (Fig. 4) without fibrosin bodies, measuring (25-)26-37(-40.5) × (12-)13-16.5(-17.5) μm. The teleomorph was lacking. DNA was extracted and an ITS sequence was obtained as described previously (3). BLAST searches of the NCBI nucleotide database (www.ncbi.nlm.nih.gov) indicated that the sequences with highest similarity were from Erysiphe pisi (97% identity) and E. diffusa (96% identity). No sequences from E. peruviana were available for comparison. A voucher specimen was deposited with the Mycological Herbarium at Washington State University. The ITS sequence was deposited with NCBI.