''Cronartium quercuum'', also known as pine-oak gall rust is a fungal disease of

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accep ...

(''Pinus'' spp.) and

oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...

(''Quercus'' spp.) trees. Similar to

pine-pine gall rust Pine-pine gall rust, also known as western gall rust, is a fungal disease of pine trees. It is caused by ''Endocronartium harknessii'' (asexual name is ''Peridermium harknessii''), an autoecious, endocyclic, rust fungus that grows in the vascular ...

, this disease is found on pine trees but its second host is an oak tree rather than another pine.

Hosts and symptoms

The pathogen requires pine and oak trees to complete its life cycle.

Aecial An aecium (plural aecia) is a specialised reproductive structure found in some plant pathogenic rust fungi that produce aeciospores. Aecia may also be referred to as "cluster cups". The term aecidium (plural aecidia) is used interchangeably but i ...

hosts in North America are two- and three-needled ''Pinus'' spieces. ''Pinus'' hosts include Austrian ('' P. nigra''), Jack pine ('' P. banksiana''), Mugo pine ('' P. mugo''), Red pine ('' P. resinosa''), Ponderosa pine ('' P. ponderosa''), and Scots pine ('' P. sylvestris''). Telial hosts are ''Quercus'' species. ''Quercus'' hosts are generally made up of the red oak group and include Northern pin oak ('' Q. ellipsoidalis''), Bur oak ('' Q. macrocarpa''), Pin oak ('' Q. palustris''), and Northern red oak (''

Q. rubra ''Quercus rubra'', the northern red oak, is an oak tree in the red oak group (''Quercus'' section ''Lobatae''). It is a native of North America, in the eastern and central United States and southeast and south-central Canada. It has been introdu ...

'').

Gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...

s start to form as slight, rounded swelling on the tree stem, then grow to become spherical and elongate. Inside the galls are

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

e which occur in rays. Hyphae are typically found in the bark, as opposed to the wood. In the spring, aecia break through the bark covering the galls. Galls that form on branches of older pine trees cause only a little damage. Although infected seedlings could have severely stunted growth or even die off.Data Sheets on Quarantine PestsCronartium quercuumEPPO quarantine pest
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Distribution

''Cronartium quercuum'' is found throughout North, Central, and South America, the Caribbean, and Asia. In North America, ''C. quercuum'' is found in Canada, the United States, and Mexico. ''C. quercuum'' is typically found in the eastern United States, spreading as far west as the Great Lakes region. Within Asia, ''C. quercuum'' is found in China, India, Japan, the Republic of Korea, the Democratic People's Republic of Korea, and the Philippines.

Life cycle

Pycnia Pycniospores are a type of spore in fungi. They are produced in special cup-like structures called pycnia or pynidia. Almost all fungi reproduce asexually with the production of spores. Spores may be colorless, green, yellow, orange, red, brown or ...

and aecia are produced on pine host in the spring and early summer one to several years after infection. The aecia usually appear one year after the pycnia arise. Aeciospores move by wind to infect the telial host (''Quercus''). Because they move by wind, aeciospores are able to travel long distances to infect the telial host. The aeciospores are unable to re-infect pine species. Uredinia form on the oak species 1-3 weeks after infection, telia develop about 15 days later.

Teliospores Teliospore (sometimes called teleutospore) is the thick-walled resting spore of some fungi ( rusts and smuts), from which the basidium arises. Development They develop in '' telia'' (sing. ''telium'' or ''teliosorus''). The telial host is the p ...

germinate and produce basidiospores.

Basidiospores A basidiospore is a reproductive spore produced by Basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are pro ...

are also wind-dispersed and travel to infect first-year pine needles. The telial host can't be re-infected by basidiospores. Basidiospore infection occurs in summer and fall. The life cycle is complete when ''Pinus'' is infected by basidiospores.

Management

Management of pine-oak gall rust is fairly simple and straightforward. Prune out galls to reduce spreading of spores to nearby pine or oak trees. Prune galls from pine branches in the late winter or early spring.

References

__FORCETOC__ {{Taxonbar, from=Q10461913 Pucciniales Tree diseases