New Disease Reports
New Disease Reports (2017) 36, 3. [http://dx.doi.org/10.5197/j.2044-0588.2017.036.003]
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First confirmed report of powdery mildew (Erysiphe sp.) on Plumeria pudica in the United States

S.N. Suarez 1, G. Sanahuja 1*, P. Lopez 1 and D.L. Caldwell 2

*g.sanahuja@ufl.edu

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Received: 12 Jun 2017; Published: 20 Jul 2017

Keywords: frangipani, ornamentals, tropical foliage

Plumeria pudica (Apocynaceae), commonly known as bridal bouquet, is a flowering ornamental plant related to the common frangipani, P. rubra. A native to Columbia, Panama and Venezuela, P. pudica has striking white flowers and a long blooming period which have made it a popular landscape plant in south Florida and the Caribbean. 

In January 2017, P. pudica leaves from a residential area in Naples, Florida, showing white powdery mycelial growth on the upper leaf surfaces were submitted to the Florida Extension Plant Diagnostic Clinic. Conidia, measuring 35 to 45 (36.7 ±1.01 μm) × 15 to 25 μm (19.47 ±0.49 μm) (n = 19), were borne on erect, cylindrical conidiophores containing a foot-cell usually equal to or shorter than the one to two cells above it. No chasmothecia were found. Based on these morphological characteristics, the pathogen was identified as an anamorph of the genus Eryisphe, with a Pseudoidium type of conidial formation, sensu Cook et al. (1997). To confirm this identification, DNA was extracted and the complete internal transcribed spacer (ITS) regions ITS1 and ITS4 of an isolate (GenBank Accession No. MF092833) were sequenced. The sequences showed 98% identity with the ITS sequence of E. elevata isolated from Catalpa bignonioides (southern catalpa) in Korea (KF840721; Cho et al., 2014) and in the UK (AY587014; Cook et al., 2000). Erysiphe elevata has previously been reported in North America causing powdery mildew on C. bignonioides which is a member of the family Bignoniaceae (Ale-Agha et al., 2004). However, in the absence of chasmothecia this pathogen will be referred to as Erysiphe sp. 

A pathogenicity test was conducted by pressing a leaf of P. pudica with heavy sporulation onto leaves of three healthy plants of the same species. Plants were kept under 60% shade at an average temperature of 24°C and 76% relative humidity. A non-infected leaf pressed onto leaves of a healthy plant served as the control. Inoculated leaves developed symptoms of the pathogen after 12 days, while the control plants remained disease-free. 

Although there are anecdotal references to powdery mildew on P. rubra, to our knowledge, this is the first confirmed report of an Erysiphe sp infecting P. pudica in the United States.

Figure1+
Figure 1: Leaves of Plumeria pudica infected with Erysiphe sp.
Figure 1: Leaves of Plumeria pudica infected with Erysiphe sp.
Figure2+
Figure 2: Mycelia and conidia of Erysiphe sp. on adaxial leaf surface of Plumeria pudica.
Figure 2: Mycelia and conidia of Erysiphe sp. on adaxial leaf surface of Plumeria pudica.
Figure3+
Figure 3: Conidia of Erysiphe sp.
Figure 3: Conidia of Erysiphe sp.

Acknowledgements

The authors would like to thank Michelle Finnegan for first bringing this disease to our attention and providing more specimens for research. 

References

  1. Ale-Agha N, Bolay A, Braun U, Feige B, Jage H, Kummer V, Lebeda A, Piątek M, Shin HD, Zimmermannová-Pastirčaková K, 2004. Erysiphe catalpae and Erysiphe elevata in Europe. Mycological Progress 3, 291. [http://dx.doi.org/10.1007/s11557-006-0099-3]
  2. Cho SE, Lee SK, Lee SH, Lee CK, Shin HD. 2014. First report of powdery mildew caused by Erysiphe elevata on Catalpa bignonioides in Korea. Plant Disease 98, 856. [http://dx.doi.org/10.1094/PDIS-12-13-1240-PDN]
  3. Cook RTA, Inman AJ, Billings C, 1997. Identification and classification of powdery mildew anamorphs using light and scanning electron microscopy and host range data. Mycological Research 101, 975-1002. [http://dx.doi.org/10.1017/S095375629700364X]
  4. Cook RTA, Henricot B, Henrici A, Beales P, 2006. Morphological and phylogenetic comparisons amongst powdery mildews on Catalpa in the UK. Mycological Research 110, 672-85. [http://dx.doi.org/10.1016/j.mycres.2006.02.005]
  5. Cook RTA, Henricot B, Kiss L, 2000. First record of Erysiphe elevata on Catalpa bignonioides in the UK. Plant Pathology 53, 807. [http://dx.doi.org/10.1111/j.1365-3059.2004.01077.x]
To cite this report: Suarez SN, Sanahuja G, Lopez P, Caldwell DL, 2017. First confirmed report of powdery mildew (Erysiphe sp.) on Plumeria pudica in the United States. New Disease Reports 36, 3. [http://dx.doi.org/10.5197/j.2044-0588.2017.036.003]

©2017 The Authors