Brown felt layer mushroom
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Brown felt layer mushroom ( Amylostereum areolatum , brown) on already slightly rotten wood |
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| Amylostereum areolatum | ||||||||||||
| ( Chaillet ex Fr. ) Boidin |
The Braunfilzige layer mushroom ( Amylostereum areolatum ) or spruce-layer mushroom is a saprobiontischer fungus from the order of Täublingsartigen (Russulales). It lives in symbiosis with wood wasps of the genus Sirex , which it enables the infestation of conifers by causing white rot there . The wasps lay their eggs together with spores of the fungus under the bark of the host trees, where the brown felted layer fungus slowly decomposes the wood and serves as food for the larvae after hatching. Then its spores get back outside with the hatching females, where the two symbionts attack trees again.
In connection with the introduction of the blue spruce wasp ( Sirex noctilio ) to Australia, South Africa and America, the fungus, originally native to Eurasia, has developed into a major forest pest and causes great damage in coniferous plantations.
features
Macroscopic properties
The brown felted layer mushroom forms perennial, effus reflexes to resupinate, i.e. fruit bodies attached to the tree trunk that are similar to those of the layer mushrooms ( stereum ). They grow flat out of the wood and form wavy, overlapping edges or hats on the upper side, which sometimes extend around the small fruiting bodies and thus in some cases form cup-like structures, which are not to be confused with apothecia .
The hats are about 1–2 cm from the wood and have a thickness of 1.0–1.5 cm in the middle. When fresh, they have a stiff leathery consistency; after drying they resemble firm cork . The top is hairy, felty and zoned: the outer edge is yellowish or tobacco brown, while the inside of the hat is more dark brown. In rain or very damp weather, the hat soaks up with water and becomes increasingly darker, so that it appears almost black.
The hymenium (fruit layer) is smooth, slightly bumpy and sometimes appears frosted; it is generally dry and more or less cracked. As it grows, it is initially ocher-brown; after wintering it fades into a grayish brown. If it is soaked by rainwater, it takes on a dark bluish-purple color. The layers of the hymenium and the trama are 0.5–1.2 mm thick and pale brown; they are clearly distinguished from the tobacco-brown, 0.2-0.7 mm thick hat felt by a red-brown separating layer.
Microscopic properties
The trama of the brown felted layer fungus is dimitic, that is, it consists of both generative and skeletal hyphae . The former are translucent and have buckles ; the latter bend towards the hymenium, where they form long, dense pseudocystidia. Similar structures are also present in the hymenium and subhymenium, but these are real cystids . Both pseudo- and true cystidia are 4–7 µm wide, yellowish-brown and at the tip or completely translucent. They are thick-walled and have a cylindrical to slightly spindle-like shape; at the top there are crystallized structures (incrustations) that dissolve in potassium hydroxide (KOH).
The brown felt layer fungus has amyloid spores of 5.0–8.5 × 2.5–4.0 µm in size . They are elongated, elliptical in shape and four sit on the 15–25 µm long and 3.5–5.5 µm thick basidia .
The brown felted layer mushroom can hardly be distinguished from the fir layer mushroom ( Amylostereum chailleti ), but unlike this it does not form arthrospores in culture .
Damage
The brown felted layer fungus is one of the main causes of red streaking. The infected wood under the bark initially develops whitish, then reddish streaks or stripes that run along the direction of growth. They arise when the fungus attacks the transport vessels in the xylem and feeds on the nutrients in the parenchymal cells . From there, the infestation spreads along the tracheids and causes a reddish color along the entire trunk. Symptoms caused by the wood wasp are not directly related to the fungus, such as the brown color, the drooping and shedding of needles or the appearance of small resin droplets on the trunk, which indicate boreholes.
Since the brown felted layer fungus only causes a weak white rot and grows slowly, it does not endanger the stability of the tree for a short time. Since it can live in the tree for a very long time - up to 17 years - the damage to the wood can take on greater proportions in the long run. Above all, however, in connection with the simultaneous infestation by wood wasps (Siricidae), there is a danger for infected trees, since the respective harmful effects are mutually reinforcing.
ecology
Sometimes the brown felt layer fungus attacks trees independently of other pests, but more often there is simultaneous attack by other fungi or targeted infection of the tree by wood wasps, which enter into a symbiotic relationship with the fungus.
The females of the corresponding wood wasp species have special organs on the abdomen , the so-called mycetangia . This contains oidia (small hyphae segments) of the brown felted layer fungus, together with a poisonous secretion. They put these together with their eggs under the bark. The fungus begins to break down the lignin in the wood and thus prepares the breeding ground for the larvae of the wood wasp. After hatching, the larvae not only benefit from the “preparatory work” of the fungus, but also feed on its mycelium and the remaining components of the wood, which they can now break down more easily. The female larvae develop provisional mycetangia, from which they release a waxy secretion containing oidia before pupation . After pupation, this wax is transported with the help of the laying spine into the now fully developed mycetangia, where it is dissolved and the fungus multiplies. The female adults then fly out and inject the fungus into new hosts.
This extremely effective method of spreading means that the brown felted layer fungus rarely forms fruiting bodies in the wild, which it does more often in culture . He also benefits from the fact that he does not have to penetrate the bark of the trees himself and the secretion of the wasp damages the tree further, so that the fungus does not encounter much resistance. The glycosaminoglycans it contains cause the tree to concentrate more starch in the needles, while there is a starch deficiency in the bast , which indicates that the transport of photosynthetic products is being interrupted. At the same time, the tree's water cycle can be impaired, which leads to needles drying up and to the death of the phloem's companion cells . This acute stress is used by the brown felted layer fungus to spread in the wood while the tree is unable to fight it.
The brown felted layer fungus requires an ambient temperature of around 20-25 ° C and a moisture content of 20-70% of the dry matter in the infected wood. It is usually only successful if the tree cannot absorb enough moisture from the soil. At 70% and more humidity, the growth of the fungus slows down considerably, making it difficult for the larvae to drill their feeding tunnels. Below 20% saturation, the eggs and young larvae of the wasp dry up, whereby older larvae can also survive in dry wood. The moisture content of infected wood is usually around 35%. Healthy trees in locations that are rich in nutrients and water are generally immune to both wasp secretion and fungus.
The symbionts of the fungus include three species of the genus Sirex : the common wood wasp ( S. juvencus ) and the blue spruce wasp from Europe, as well as S. nitobei from East Asia. What all three species have in common is that they only enter into a symbiosis with the brown felted layer fungus. The blue spruce wasp is particularly important as a pest, as it was introduced into sensitive ecosystems.
Conifers were as hosts previously observed in the first place, so include fir ( Abies ), cedars ( Cryptomeria ), larch ( Larix ), spruce ( Picea ), pines ( Pinus ) and Douglas fir ( Pseudotsuga ) to the usual spectrum. While in Europe spruce is apparently preferred, outside of the original range pine are the most important hosts. Observations of the fungus on beeches ( Fagus ) are either absolute exceptions or they can be traced back to incorrect determination. The brown felt layer mushroom can be found at all altitudes. The fungus is particularly widespread in Europe in the hill country and in submontane locations from 200 to 1000 m; in the Alps, the occurrence also extends up to 1500 m. On the other hand, it is less common in the planar lowlands, where the spruce is only found in forestry plantations.
distribution
The temperate Holarctic represents the original distribution area of the brown felted layer fungus, whereby it was linked to the distribution of natural pine forests. With the introduction of infected wood, however, it was also able to gain a foothold in other parts of the world from the end of the 19th century.
Probably before 1900 the brown felted layer mushroom and the blue spruce wasps reached New Zealand with shiploads of infected wood . It was probably from there that it was introduced into Tasmania 50 years later , and ten years later it had also penetrated mainland Australia.
The leap to South America took place in 1980 when the fungus was detected in Uruguay , from there it spread to Argentina , Brazil and Chile . In 1994 the brown felted layer mushroom finally reached South Africa . The spruce wasp was detected in the Great Lakes area around 2004 , which also affected the North American continent for the first time. The blue spruce wasp is currently known from five US states and the province of Ontario .
The spread of wasps is expected to increase further in the future, so a large part of the world's temperate climatic zones should be populated with pine trees by the fungus. However, Western Australia, East Africa and northwestern South America are exempt, provided the fungus and wasp are not introduced into these areas.
Systematics
The brown felt layer mushroom is, next to the fir layer mushroom ( A. chailletii ), the only species of the genus Amylostereum that enters into a symbiosis with wood wasps. It is less closely related to the other three members of the genus than they are to each other. This can be seen, among other things, in the fact that its mycelium is incompatible with that of other amylostereum species, i.e. it does not combine with that of the other species.
In contrast, German Krieglsteiner takes the view that the brown felted layer mushroom and the fir layer mushroom are one and the same species in different stages of ripeness. The latter represents the juvenile, the brown felted layer fungus the adult stage. He justifies this with the inter-sterility of the two fungi and their only marginal microscopic differences.
A fungus of the genus Amylostereum that has not yet been clearly identified may represent the link between the species associated with wood wasps and the non-symbiotic species. The relationships between the brown felted layer fungus are shown in the following cladogram :
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Significance as a forest pest and measures to combat it
Effect on the tree population
While the brown felted layer fungus does not pose a major threat to the tree population in its original area of distribution, it has developed into a serious pest in forestry, especially in the southern hemisphere. The financial damage in eastern Canada alone is estimated at 2.1 billion US dollars by 2037. Fast-growing pine monocultures in particular are susceptible to infestation by the blue spruce wasp and the brown felted layer fungus.
In addition to the absence of the wasp's original predator, the condition of the trees also plays a role. Weakened and sick trees are apparently deliberately selected by the wasp, whereby it is apparently based on essential oils that are increasingly secreted by weak trees. Trees with sufficient water and nutrient supply are usually able to fight off the fungus, which also prevents the wasp larvae from developing. So far, research has focused primarily on the effects on introduced tree species; the influence on tree species native to the southern hemisphere has hardly been researched. The appearance of the symbionts in the United States may lead to a decline in native wood wasp species, but otherwise to an increase in other tree-damaging insects and fungi.
Containment and control
Problems with the containment of the Sirex - amylostereum complex are mainly caused by the high rate of spread of the two species; the rate of spread of the blue spruce wasp is 20–50 km per year. The spread is only stopped by correspondingly wide bodies of water or treeless areas, which means that East Africa, for example, has not yet been affected. Despite increased caution when importing wood, the blue spruce wasp also managed to cross these natural boundaries, making spatial containment almost impossible. As a precaution, however, timber imports into the United States are treated with pesticides to kill larvae hidden in the wood. In Australia and New Zealand, vulnerable Monterey pines ( Pinus radiata ) are preemptively felled in order to deprive the wasp of their habitat. In the United States, forest authorities are trying to limit the spread of the fungus by running information campaigns warning against the transport of infected firewood.
The use of insecticides against the swarming wasps shows hardly any effect, since the adult animals only have a short life span and do not eat any food. On the other hand, hopes are directed towards the parasites of the blue spruce wood wasp. A promising method of combating the Sirex - amylostereum complex is infection of the wasps by the nematode Deladenus siricidicola . It goes through two stages of development: First, it feeds on the mycelium of the fungus as long as it lives in the wood of the tree that has been infected by wasp and fungus. With the fungus it gets into the body of the larvae and finally the adult females. There it triggers extensive sterility; the wasp continues to inject the fungus and nematode into trees, but has far fewer offspring than healthy conspecifics. This method has proven to be particularly effective in Australia, New Zealand and South America.
Sources and References
literature
- Angus J. Carnegie et al. a .: Predicting the potential distribution of Sirex noctilio (Hymenoptera: Siricidae), a significant exotic pest of Pinus plantations. In: Annals of Forest Science 63, 2006. pp. 119-128.
- J. Boidin , P. Lanquetin: Le genre Amylostereum (Basidiomycetes) intercompatibilités entre espèces allopatriques. In: Bulletin de la Societé Mycologique de France 100, No. 2, 1984. pp. 211-236.
- R. Felini: Deladenus siricidicola , Bedding (Neotylenchidae) parasitism evaluation in adult Sirex noctilio , Fabricius , 1793 (Hymenoptera: Siricidae). In: Revista Brasileira de Biologia 60, No. 4 November 2000.
- Harry J. Hudson: Fungal Biology . CUP Archive, 1992. ISBN 0-521-42773-8 , pp. 248-252.
- Hermann Jahn : Steroids mushrooms in Europe (Stereaceae Pil. Emend. Parm. And others, Hymenochaete) with special consideration of their occurrence in the Federal Republic of Germany. In: Westfälische Pilzbriefe 8, No. 4–7 1971. pp. 69–119 (online as PDF; 3.08 MB ).
- German Josef Krieglsteiner (Ed.): The large mushrooms of Baden-Württemberg . Volume 1: General Part. Stand mushrooms: jelly, bark, prick and pore mushrooms. Ulmer, Stuttgart 2000, ISBN 3-8001-3528-0 , pp. 151-152.
- Bernard Slippers et al. a .: Relationships among Amylostereum species associated with siricid woodwasps inferred from mitochondriam mitochondrial DNA sequences. In: Mycologia 92, No. 5 2000. pp. 955-963 (online as PDF; 748 kB ).
- Masanobu Tabata et al. a .: Molecular phylogeny of species in the genera Amylostereum and Echinodontium . In: Mycoscience 41, 2000. pp. 585-593.
- Charles L. Thayer: Amylostereum areolatum (Fr.) Boidin . Sirex Fungus Pest Fact Sheet. United States Department of Agriculture, Animal and Plant Health Inspection Service. Center for Plant Health Science and Technology, 2007. pp. 1-10.
Web links
- Amylostereum areolatum on www.indexfungorum.org
- D. Chalkley: Diagnostic Fact Sheet for Amylostereum areolatum . Systematic Mycology and Microbiology Laboratory, ARS, USDA.
Individual evidence
- ↑ a b c d e f Hermann Jahn : Steroids mushrooms in Europe (Stereaceae Pil. Emend. Parm. Et al., Hymenochaete) with special consideration of their occurrence in the Federal Republic of Germany. In: Westfälische Pilzbriefe 8, No. 4-7 1971. pp. 98-100.
- ↑ a b Bernard Slippers u. a .: Relationships among Amylostereum species associated with siricid woodwasps inferred from mitochondriam mitochondrial DNA sequences. In: Mycologia 92, No. 5 2000. pp. 955-963.
- ↑ Photo of a damaged tree. www.forestryimages.org. Retrieved February 27, 2010.
- ↑ a b c d e f g D. Chalkley: Diagnostic Fact Sheet for Amylostereum areolatum . ( Memento of the original from September 27, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved March 1, 2010.
- ↑ Olaf Schmidt, Dieter Czeschlik: Wood and Tree Fungi: Biology, Damage, Protection, and Use. Springer, 2006. ISBN 3-540-32138-1 , pp. 129-131.
- ↑ a b c d e Charles L. Thayer: Amylostereum areolatum (Fr.) Boidin. Sirex Fungus Pest Fact Sheet. United States Department of Agriculture, Animal and Plant Health Inspection Service. Center for Plant Health Science and Technology, 2007. pp. 1-10.
- ↑ a b c d Harry J. Hudson: Fungal Biology . CUP Archive, 1992. ISBN 0-521-42773-8 , pp. 248-252.
- ↑ a b German Josef Krieglsteiner (Ed.): Die Großpilze Baden-Württemberg. Volume 1: General Part. Stand mushrooms: jelly, bark, prick and pore mushrooms. Ulmer, Stuttgart 2000, ISBN 3-8001-3528-0 , pp. 151-152.
- ↑ Angus J. Carnegie et al. a .: Predicting the potential distribution of Sirex noctilio (Hymenoptera: Siricidae), a significant exotic pest of Pinus plantations. In: Annals of Forest Science 63, 2006. pp. 119-128.
- ↑ Masanobu Tabata et al. a .: Molecular phylogeny of species in the genera Amylostereum and Echinodontium . In: Mycoscience 41, 2000. pp. 585-593.
- ↑ R. Felini: Deladenus siricidicola , Bedding (Neotylenchidae) parasitism evaluation in adult Sirex Noctilio , Fabricius 1793 (Hymenoptera: Siricidae). In: Revista Brasileira de Biologia 60, No. 4 November 2000.
