''Ophiognomonia clavigignenti-juglandacearum'' is a
mitosporic fungus
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
that causes the butternut canker, a lethal disease of
butternut trees (''Juglans cinerea''). It is also known to parasitize other members of the genus ''
Juglans
Walnut trees are any species of tree in the plant genus ''Juglans'', the type genus of the family (biology), family Juglandaceae, the seeds of which are referred to as walnuts. All species are deciduous trees, tall, with pinnate leaves , with ...
'' on occasion, and very rarely other related trees including
hickories.
The fungus is found throughout
North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, occurring on up to 91% of butternut trees, and may be threatening the viability of butternut as a species.
Distribution
Butternut, the
primary host of ''O. clavigignenti-juglandacearum'', is found in mixed hardwood forests throughout central North America, from
New Brunswick
New Brunswick is a Provinces and Territories of Canada, province of Canada, bordering Quebec to the north, Nova Scotia to the east, the Gulf of Saint Lawrence to the northeast, the Bay of Fundy to the southeast, and the U.S. state of Maine to ...
to
North Carolina
North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...
.
The pathogen was identified as an
invasive species
An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
in 1967. It was first discovered in
Wisconsin
Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig ...
, but has since spread to other states and into
Canada
Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
,
making the butternut an
endangered species
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...
in
Ontario
Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...
.
Its native origin is unknown, but possibly in
Asia
Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
given the resistance of Asian walnuts to the disease.
[ The ]United States Forest Service
The United States Forest Service (USFS) is an agency within the United States Department of Agriculture, U.S. Department of Agriculture. It administers the nation's 154 United States National Forest, national forests and 20 United States Natio ...
found that 84% of all butternuts in Michigan
Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...
as well as 58% of all trees from Wisconsin have been affected;Wisconsin Department of Natural Resources
The Wisconsin Department of Natural Resources (WDNR) is a government agency of the U.S. state of Wisconsin charged with conserving and managing Wisconsin's natural resources. The Wisconsin Natural Resources Board has the authority to set polic ...
revealed that 91% of all living trees in Wisconsin were diseased or cankered. In Virginia
Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...
and North Carolina
North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...
, the butternut population has been reduced from 7.5 million to 2.5 million.
Symptoms
Broad dead areas known as cankers form on the main stem, branches, young twigs, and exposed roots. Most cankers are covered with bark
Bark may refer to:
Common meanings
* Bark (botany), an outer layer of a woody plant such as a tree or stick
* Bark (sound), a vocalization of some animals (which is commonly the dog)
Arts and entertainment
* ''Bark'' (Jefferson Airplane album), ...
cracks. The fungus forms a dark mat of branching mycelium
Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...
below the bark, from which arise peg-like 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 o ...
that lift and rupture the bark. In the later stages of infection, the bark above the canker is shredded.
Life cycle
''O. clavigignenti-juglandacearum'' produces its spores asexually; its sexual form of reproduction has never been observed.