Fungalpedia – Note 261Valdensia


Valdensia Peyronel.

Citation when using this entry: Aumentado et al. 2024 (in prep) – Fungalpedia, plant pathogens. 

Index FungorumFacesoffungiMycoBankGenBank, Fig. 1.

Classsification: Sclerotiniaceae, Helotiales, Leotiomycetidae, Leotiomycetes, Pezizomycotina, Ascomycota, Fungi

Valdensia was introduced by Peyronel (1923) and typified with Valdensia heterodoxa. Valdensia (asexual) and Valdensinia (sexual) have the same type of species and are generic synonyms; however, including Asterobolous, Johnston et al. (2014) proposed to conserve the former over the latterThis monotypic genus is characterised by its star-shaped conidia (stauroconidia), which are stellate, thick-walled, range from hyaline to pale brown, and are typically surrounded by a whorl of four or five appendages (Nekoduka et al. 2012) to three to six (Abbasi et al. 2023). Conidia have a single row of 8–10 closely spaced, thin-walled, transverse swellings on the proximal sections of the upper surfaces of the appendages, whereas the distal portion of the appendages is subulated and sparsely granulated. As the conidia matured, the appendages folded completely, resulting in a teardrop shape. The hemispherical conidial head consists of approximately 150 cells that germinate to produce infective hyphae (Redhead & Perrin 1972), and are coated with mucus, facilitating adhesion to leaf surfaces (Abbasi et al. 2023). Multiple germ tubes with branched appressoria emerge from the conidial head to infect host tissues (Norvell & Redhead 1994Zhao and Shamoun 2006Nekoduka et al. 2012). Single conidia, recently infecting a leaf, are often visible to the naked eye at the center of lesions (Redhead and Perrin 1972Hildebrand and Renderos 2007Nekoduka et al. 2012). The ITS molecular sequence data are available (Nekoduka et al. 2012Kukula et al. 2017). 

Since the initial documentation of Valdensia in Italy (Peyronel 1923) that affected Vaccinium myrtillus L., it has subsequently been observed in various European countries, Russia, Japan, and North America, infecting over 60 plant species (Peyronel 1927Gjerum 1970Redhead 1979Norvell & Redhead 1994Mulenko & Woodward 1996Melnik et al. 2007Mulenko et al. 2008Nekoduka et al. 2012Dzięcioł et al. 2014Farr & Rossman 2024). However, it is primarily associated with hosts of the Ericaceae family, including Vaccinium and Gaultheria as reported by several studies (Mulenko & Woodward 1996Nekoduka et al. 2012Abbasi et al. 2023). The primary symptoms manifest as circular, desiccated patches on the leaves, often encircled by a brown or reddish ring, and the colour intensity is influenced by sunlight exposure (Peyronel 1923Hildebrand & Renderos, 2017). It is hypothesised that anthocyanins produced in infected leaves exposed to light contribute to the leaf’s resistance against fungal activity, resulting in smaller spots compared to shaded plants (Peyronel 1923). 

Pathogenicity assays in  Vaccinium spp. resulted in an infection success rate of more than 50% (Lyon et al. 2015), whereas assays by Nekoduka et al. (2012) and Kukula et al. (2017) caused small necrotic lesions on young detached leaves of Vaccinium spp. that developed into large rings. Norvell & Redhead (1994) presumed that this fungus could lead to a 20% reduction in green foliage in North America. Furthermore, it is being investigated as a possible bioherbicide for the management of ericaceous shrubs (Wilkin et al. 2005). If fields are not treated with fungicide, yield loss during the fruiting year can surpass 60% (Hildebrand & Renderos 2007). However, even in sprouts, yield can be affected by defoliation (Abbasi et al. 2023).

Type species: Valdensia heterodoxa Peyronel

Other species: This genus is monotypic.                                   

Figure 1 – Valdensia heterodoxa. a Symptoms on leaves and fruit of Vaccinium angustifolium. b Mature and immature conida. c Teardrop-shaped conidium after downfolding of appendages. d Single series of closely packed transverse swellings (arrows) on proximal portion of upper surface of appendages. e Distal portion of appendage with subulate and sparsely granulate surface (arrows). Scale bars: b = 150 µm; c = 100 µm; d–e = 20 µm. Redrawn from Abbasi et al. (2023) and Nekoduka et al. (2012).



Abbasi PA, Hildebrand PD, Ali S, Wright H et al. 2023 – Effects of temperature and wetness on components of the infection cycle of Valdensia heterodoxa in lowbush blueberry. Plant Disease, 107(1), 167–76.

Dzięcioł R, Mirzwa-Mróz E, Zielińska E, Wińska-Krysiak M et al. 2014 – Valdensinia heterodoxa Peyronel as a new pathogen of blueberry in Poland. Plant Disease, 98(5), 688.

Farr DF, Rossman AY. 2024 – Fungal databases. U.S. National Fungus Collections, ARS, USDA.

Gjerum HB. 1970 – A curious fungus on Vaccinium myrtillus. Blyttia, 3, 159–63.

Hildebrand PD, Renderos WE. 2007 – Valdensinia leaf spot (Valdensinia heterodoxa) of commercial lowbush blueberry in Atlantic Canada: An emerging new threat. Can. J. Plant Pathol., 29, 90. 

Hildebrand PD, Renderos WE. 2017 – Septoria leaf spot and stem canker. In Compendium of Blueberry, Cranberry, and Lingonberry Diseases and Pests, 54–7.

Johnston PR, Seifert KA, Stone JK, Rossman AY et al. 2014 – Recommendations on generic names competing for use in Leotiomycetes (Ascomycota). IMA fungus, 91–120.

Kukuła W, Mirzwa-Mróz E, Wakuliński W, Paduch-Cichal E. 2017 – Characteristics of Valdensia heterodoxa Peyr. as an Ericaceae pathogen in Poland. Acta Scientiarum Polonorum Hortorum Cultus, 16(4), 101–12.

Lyon E. 2015 – Dispersal and Establishment of the Fungal Pathogen, Valdensia heterodoxa, in Maine, 143 in: M. Sc Thesis. The University of Maine, Orono, ME.

Melnik VA, Popov ES, Shabunin DA. 2007 – Contributions to the studies of mycobiota in Novgorod and Pskov regions. I. Hyphomycetes. Mikologiia i Fitopatologiia, 41(6), 515.

Mulenko W, Woodward S. 1996 –Plant parasitic hyphomycetes new to Britain. Mycologist, 10(2), 69–x5.

Mułenko W, Majewski T, Ruszkiewicz-Michalska M. 2008 – A preliminary checklist of micromycetes in Poland. Pol. Acad. Sci., 9, 752.

Nekoduka S, Kanematsu S, Tanaka K, Harada Y et al. 2012 – Valdensia leaf blight of highbush blueberry caused by Valdensinia heterodoxa, a new fungal disease in Japan. Journal of General Plant Pathology, 78, 151–9.

Norvell LL, Redhead SA. 1994 – Valdensinia heterodoxa (Sclerotiniaceae) in the United States. Canadian Journal of Forest Research,  24(9), 1981–3.

Peyronel B. 1923 – On a singular polyphagous parasite: Valdensia heterodoxa n. gen. et n. sp. Staz. Sperim. Agrar. Italiane..;56 (10-12), 521–38.

Peyronel B. 1927 – Nuove osservazioni sulla biologia e sulla distribuzione geografica della Valdensia heterodoxa. Boll Staz Patol Veg Roma, 7, 3–14.

Redhead SA, Perrin PW. 1972 – Asterobolus: a new parasitic hyphomycete with a novel dispersal mechanism. Canadian Journal of Botany, 50(3), 409–12.

Redhead SA. 1979 – Mycological observations: 1, on Cristulariella; 2, on Valdensinia; 3, on Neolecta. Mycologia, 71, 1248–1253

Wilkin JE, Ritland C, Ritland K, El-Kassaby YA et al. 2005 – Genetic diversity and population structure of Valdensinia heterodoxa, a potential biocontrol agent for salal in coastal British Columbia. Canadian Journal of Plant Pathology, 27(4), 559–71.

Zhao S, Shamoun SF. 2006 – The effects of culture media, solid substrates, and relative humidity on growth, sporulation and conidial discharge of Valdensinia heterodoxa. Mycological Research, 110(11), 1340–6.


Entry by

Herbert Dustin R. Aumentado, Center of Excellence in Fungal Research and School of Science, Mae Fah Luang University, Chiang Rai, Thailand 


(Edited by Ruvishika S. Jayawardena, Kevin D. Hyde, Samaneh Chaharmiri-Dokhaharani, & Achala R. Rathnayaka)


Published online 21 May 2024