Chondrostereum purpureum
Encyclopedia
Silver leaf is a fungal
disease of tree
s caused by the fungus plant pathogen Chondrostereum purpureum. It attacks most species of the rose family Rosaceae
, particularly the genus Prunus
. The disease is progressive and often fatal. The common name is taken from the progressive silvering of leaves on affected branches. It is spread by airborne spore
s landing on freshly exposed sapwood. For this reason cherries
and plum
s are pruned in summer, when spores are least likely to be present and when disease is visible. Silver Leaf can also happen on poming fruits like apples and pear
s. Plum
s are especially vulnerable.
In the past the name Stereum purpureum Pers. was widely used for this fungus, but according to modern taxonomy it is only distantly related to Stereum
, actually belonging to order Polyporales
whereas Stereum is in order Russulales
.
The spores are rounded cylinders approximately 5-8 µm x 3-4 µm in size. The hypha
l structure is monomitic with clamp connection
s.
It is often found on old stumps and dead wood, but can also be a serious parasite of living trees. As well as plum trees it attacks many other broad-leafed species (other Prunus
, apple
, pear
, willow
, poplar
, maple
, hornbeam
, plane
, oak
, elm
, lilac
, and many others). Occasionally it also infects conifers (fir
, spruce
, Thuja
, ...). Geographically it is roughly speaking just as widespread as its hosts - it is common in woods, orchards and tree plantations in temperate climates.
, aspen
s and other species. The fungus is applied directly to the weed trees in a nutrient paste which can be stored and handled conveniently. According to a report of the Canadian Pest Management Agency, the use of this control method will only have a limited impact on non-target trees since the fungal spores are ubiquitous anyway and healthy trees are resistant to attack.
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
disease of tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s caused by the fungus plant pathogen Chondrostereum purpureum. It attacks most species of the rose family Rosaceae
Rosaceae
Rosaceae are a medium-sized family of flowering plants, including about 2830 species in 95 genera. The name is derived from the type genus Rosa. Among the largest genera are Alchemilla , Sorbus , Crataegus , Cotoneaster , and Rubus...
, particularly the genus Prunus
Prunus
Prunus is a genus of trees and shrubs, which includes the plums, cherries, peaches, apricots and almonds. There are around 430 species spread throughout the northern temperate regions of the globe. Many members of the genus are widely cultivated for fruit and ornament.-Botany:Members of the genus...
. The disease is progressive and often fatal. The common name is taken from the progressive silvering of leaves on affected branches. It is spread by airborne spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s landing on freshly exposed sapwood. For this reason cherries
Cherry
The cherry is the fruit of many plants of the genus Prunus, and is a fleshy stone fruit. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium....
and plum
Plum
A plum or gage is a stone fruit tree in the genus Prunus, subgenus Prunus. The subgenus is distinguished from other subgenera in the shoots having a terminal bud and solitary side buds , the flowers in groups of one to five together on short stems, and the fruit having a groove running down one...
s are pruned in summer, when spores are least likely to be present and when disease is visible. Silver Leaf can also happen on poming fruits like apples and pear
Pear
The pear is any of several tree species of genus Pyrus and also the name of the pomaceous fruit of these trees. Several species of pear are valued by humans for their edible fruit, but the fruit of other species is small, hard, and astringent....
s. Plum
Plum
A plum or gage is a stone fruit tree in the genus Prunus, subgenus Prunus. The subgenus is distinguished from other subgenera in the shoots having a terminal bud and solitary side buds , the flowers in groups of one to five together on short stems, and the fruit having a groove running down one...
s are especially vulnerable.
In the past the name Stereum purpureum Pers. was widely used for this fungus, but according to modern taxonomy it is only distantly related to Stereum
Stereum
Stereum is type genus of the Stereaceae family of fungi, in the Russulales order. Until recently, the genus was classified in the Corticiaceae family, of the Corticiales order. However, it was given its own family as a result of the split-up of the Corticiales. Common names for species of this...
, actually belonging to order Polyporales
Polyporales
The Polyporales are an order of fungi in the class Agaricomycetes. The order includes some polypores as well as many corticioid fungi and a few agarics . Species within the order are saprotrophic, most of them wood-rotters...
whereas Stereum is in order Russulales
Russulales
The Russulales are an order of the Agaricomycetes,...
.
Characteristics
After starting as just a crust on the wood, the fruiting structure develops undulating intergrowing brackets up to about 3 cm broad, which have a tough rubbery texture. The edges and fertile lower surfaces show a fairly vivid violet colour while the fungus is growing, and the upper surfaces have a grey aspect (sometimes with zonation) and are covered with whitish hairs. After a week or two the fructification dries out, becomes brittle, and turns a drab brown or beige. Infected wood can be recognized because it is stained a darker tint.The spores are rounded cylinders approximately 5-8 µm x 3-4 µm in size. The hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
l structure is monomitic with clamp connection
Clamp connection
A clamp connection is a structure formed by growing hyphal cells of certain fungi. It is created to ensure each septum, or segment of hypha separated by crossed walls, receives a set of differing nuclei, which are obtained through mating of hyphae of differing sexual types...
s.
It is often found on old stumps and dead wood, but can also be a serious parasite of living trees. As well as plum trees it attacks many other broad-leafed species (other Prunus
Prunus
Prunus is a genus of trees and shrubs, which includes the plums, cherries, peaches, apricots and almonds. There are around 430 species spread throughout the northern temperate regions of the globe. Many members of the genus are widely cultivated for fruit and ornament.-Botany:Members of the genus...
, apple
Apple
The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...
, pear
Pear
The pear is any of several tree species of genus Pyrus and also the name of the pomaceous fruit of these trees. Several species of pear are valued by humans for their edible fruit, but the fruit of other species is small, hard, and astringent....
, willow
Willow
Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...
, poplar
Poplar
Populus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....
, maple
Maple
Acer is a genus of trees or shrubs commonly known as maple.Maples are variously classified in a family of their own, the Aceraceae, or together with the Hippocastanaceae included in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group system, favour inclusion in...
, hornbeam
Hornbeam
Hornbeams are relatively small hardwood trees in the genus Carpinus . Though some botanists grouped them with the hazels and hop-hornbeams in a segregate family, Corylaceae, modern botanists place the hornbeams in the birch subfamily Coryloideae...
, plane
Platanus
Platanus is a small genus of trees native to the Northern Hemisphere. They are the sole living members of the family Platanaceae....
, oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
, elm
Elm
Elms are deciduous and semi-deciduous trees comprising the genus Ulmus in the plant family Ulmaceae. The dozens of species are found in temperate and tropical-montane regions of North America and Eurasia, ranging southward into Indonesia. Elms are components of many kinds of natural forests...
, lilac
Lilac
Syringa is a genus of about 20–25 species of flowering woody plants in the olive family , native to woodland and scrub from southeastern Europe to eastern Asia, and widely and commonly cultivated in temperate areas elsewhere....
, and many others). Occasionally it also infects conifers (fir
Fir
Firs are a genus of 48–55 species of evergreen conifers in the family Pinaceae. They are found through much of North and Central America, Europe, Asia, and North Africa, occurring in mountains over most of the range...
, spruce
Spruce
A spruce is a tree of the genus Picea , a genus of about 35 species of coniferous evergreen trees in the Family Pinaceae, found in the northern temperate and boreal regions of the earth. Spruces are large trees, from tall when mature, and can be distinguished by their whorled branches and conical...
, Thuja
Thuja
Thuja is a genus of coniferous trees in the Cupressaceae . There are five species in the genus, two native to North America and three native to eastern Asia...
, ...). Geographically it is roughly speaking just as widespread as its hosts - it is common in woods, orchards and tree plantations in temperate climates.
A biological control agent
C. purpureum is commercially available as a method of combatting forest "weed" trees such as red alderRed Alder
Alnus rubra, the Red alder, is a deciduous broadleaf tree native to western North America.-Description:It is the largest species of alder in North America and one of the largest in the world, reaching heights of 20–35 m. The official tallest red alder stands 32 meters tall in Clatsop County, Oregon...
, aspen
Aspen
Populus section Populus, of the Populus genus, includes the aspen trees and the white poplar Populus alba. The five typical aspens are all native to cold regions with cool summers, in the north of the Northern Hemisphere, extending south at high altitudes in the mountains. The White Poplar, by...
s and other species. The fungus is applied directly to the weed trees in a nutrient paste which can be stored and handled conveniently. According to a report of the Canadian Pest Management Agency, the use of this control method will only have a limited impact on non-target trees since the fungal spores are ubiquitous anyway and healthy trees are resistant to attack.