Taxonomy

Domain	Eukarya
Kingdom	Fungi
Phylum	Ascomycota
Subphylum	Pezizomycotina
Class	Sordariomycetes
Subclass	Hypocreomycetidae
Order	Hypocreales
Family	Nectriaceae
Genus	Neonectria

Scientific Name

Neonectria faginata

Scientific Name Synonyms

Neonectria coccinea var. faginata

Nectria coccinea var. faginata

Common Name

beech bark disease

Author: Maxwell Reitman, University of Florida

Reviewed by: Jeffrey Rollins, University of Florida

Pathogen

Neonectria faginata (Neonectria coccinea var. faginata) is a pathogen that infects the American Beech tree (Fagus grandifolia) causing beech bark disease (BBD). The fungus produces tiny, bright red perithecia that contain asci with ellipsoid ascospores 10.5-12.5 x 5-6µm with irregular warts. In its asexual state, it produces both 11-14 x 3µm microconidia on sporodochia and macroconidia up to 120µm.

Symptoms and Signs

BBD is characterized by the collapse of host parenchyma cells and fissuring followed by mycelial expansion. The tissue weakens and cankers oozing red-brown liquid can form along the tree. Severe cases may cause foliage loss and yellowing or even girdling. BBD disproportionately affects older trees.

Ecology and Spread

Neonectria faginata infects wounds created by the beech scale beetle (Cryptococcus fagisuga), causing BBD. The scale beetle penetrates the bark for feeding purposes, allowing N. faginata spores to enter the tree. The connection with scale beetles causes reduced prevalence of the disease during rainy and cold periods (< -34 C). The disease moves inside the bark by mycelial spread. The asexual stage of the disease is wind dispersed, while the sexual phase is dispersed by scale bug crawlers or water. Both conidia and ascospores can infect new trees.

Geographic Distribution

This pathogen is found throughout North America with suspected European origin, though no documented cases in Europe.

Management

Remove susceptible or infected trees.
Remove scale insects via scrubbing, high-pressure water, or petroleum-oils.
Select more vigorous and smooth-barked individuals.
Encourage natural scale bug predators such as gnats and mites.
Consult your local extension specialist for legal and efficacious fungicide products available in your state. Remember, the label is the law and the product applicator is responsible for reading and following all chemical labeling.

Diagnostic Procedures

Key signs to look for in infected trees include:

the presence of small, red, or orange perithecia at base of tree or surrounding cankers;
detectable scale bugs in the area;
red-brown ooze from cankers; and
conidia born on sporodochia.

Neonectria faginata will produce asci on general media, though isolation is improved by the inclusion of streptomycin and penicillin.

Resources and References

1. Neonectria faginata. Global Invasive Species Database. http://www.issg.org/database/species/ecology.asp?si=1714&fr=1&sts=tss&lang=EN

2. Neonectria faginata. Mycobank. http://www.mycobank.org/Biolomics.aspx?Table=Mycobank&MycoBankNr_=504379

Acknowledgements

National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2011-41530-30708 as part of "Diagnostic Image Series Development for Supporting IPM in the Southern Region" (USDA-NIFA-RIPM-003351)