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TABLE OF CONTENT
MICROBIAL DETERIORATION OF WOOD AND ITS CONTROL 2
Background 3
1.0 Introduction 4 1.1.1Chemistry of wood 5 1.1.2Extractives 5 1.2Environmental Factors Affecting wood decay 6
2.0 The Role of microorganisms in wood decay 7
3.0 Microbiological degradation of wood 9
3.1 Wood decaying fungi 10 3.1.1 Soft rot 10 3.1.2White rot 13 3.1.3 Bacteria 13
3.2 Mechanism of wood deterioration 14 3.2.1 Degradation of hemicelluloses 15 3.2.2 Degradation of lignin 16 3.2.3 Cellulose degradation 16
4.0CASE STUDY 19
5.0 Control of wood deterioration 21 5.1 CONCLUSION 24
REFERENCE 25

MICROBIAL DETERIORATION OF WOOD AND ITS CONTROL

BY

AGWULONU JOSEPH
SU11311020
DEPARTMENT OF MICROBIOLOGY
COLLEGE OF NATURAL AND APPLIED SCIENCES
SALEM UNIVERSITY LOKOJA, KOGI STATE.

Background
Wood is a hard, fibrous structural tissue found in the stems and roots of trees and other woody plants. It has been used for thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers (which are strong in tension) embedded in a matrix of lignin which resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by them. It also mediates the transfer of water and nutrients to the leaves and other growing tissues. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber.
However, various microorganisms attack woody trees since they are ubiquitous and this effect leads to the detrimental deterioration of wood. This paper would discuss the different microorganisms that affect woody trees, the classification of these microbes, their structure, mechanism of action and how these mechanisms can be used against them for control.

1.0 Introduction
The Earth contains about one trillion tonnes of wood, which grows at a rate of 10 billion tonnes per year. As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as a source of renewable energy. In 1991, approximately 3.5 billion cubic meters of wood were harvested. Dominant uses were for furniture and building construction (Horst et al., 2005).
Woody trees are of different types and species and they grow at different climate conditions. These include oak, pines, elm, mahogany, obeche, iroko, maple, walnut, but to mention but a few (Mimms et al.,1993).
Wood can be transformed into many different objects, such as furniture, golf clubs, boats and musical instruments.
Wood is a heterogeneous, hygroscopic, cellular and anisotropic material. It is composed of cells, and the cell walls are composed of micro-fibrils of cellulose (40% – 50%) and hemicellulose (15% – 25%) impregnated with lignin (15% – 30%). (Christina et al., 2013) In coniferous or softwood species the wood cells are mostly of one kind, tracheids, and as a result the material is much more uniform in structure than that of most hardwoods. There are no vessels ("pores") in coniferous wood such as one sees so prominently in oak and ash, for example.

The structure of hardwoods is more complex (Hardwood Structure www.uwsp.edu). The water conducting capability is mostly taken care of by vessels: in some cases (oak, chestnut, ash) these are quite large and distinct, in others (buckeye, poplar, willow) too small to be seen without a hand lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous (Sperry et al., 1994). In ring-porous species, such as ash, black locust, catalpa, chestnut, elm, hickory, mulberry,[citation needed] and oak, (Sperry et al., 1994,). the larger vessels or pores (as cross sections of vessels are called) are localised in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibers. These fiber are the elements which give strength and toughness to wood, while the vessels are a source of weakness. In diffuse-porous woods the pores are evenly sized so that the water conducting capability is scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are alder, (Sperry et al., 1994,). Basswood, birch, buckeye, maple, willow, and the Populus species such as aspen, cottonwood and poplar.( Sperry et al., 1994,).Some species, such as walnut and cherry, are on the border between the two classes, forming an intermediate group.
1.1.1Chemistry of wood The chemical composition of wood varies from species to species, but is approximately 50% carbon, 42% oxygen, 6% hydrogen, 1% nitrogen, and 1% other elements (mainly calcium, potassium, sodium, magnesium, iron, and manganese) by weight. (Jean-Pierre et al., 1996).Wood also contains sulfur, chlorine, silicon, phosphorus, and other elements in small quantity.
Aside from water, wood has three main components. Cellulose, a crystalline polymer derived from glucose, constitutes about 41–43%. Next in abundance is hemicellulose, which is around 20% in deciduous trees but near 30% in conifers. It is mainly five-carbon sugars that are linked in an irregular manner, in contrast to the cellulose. Lignin is the third component at around 27% in coniferous wood versus 23% in deciduous trees. Lignin confers the hydrophobic properties reflecting the fact that it is based on aromatic rings. These three components are interwoven, and direct covalent linkages exist between the lignin and the hemicellulose. A major focus of the paper industry is the separation of the lignin from the cellulose, from which paper is made.

In chemical terms, the difference between hardwood and softwood is reflected in the composition of the constituent lignin. Hardwood lignin is primarily derived from sinapyl alcohol and coniferyl alcohol. Softwood lignin is mainly derived from coniferyl alcohol (Boerjan et al., June 2003).

1.1.2Extractives
Aside from the lignocellulose, wood consists of a variety of low molecular weight organic compounds, called extractives. The wood extractives are fatty acids, resin acids, waxes and terpenes. For example, rosin is exuded by conifers as protection from insects. The extraction of these organic materials from wood provides tall oil, terpentine, and rosin (Fiebach et al., 2000).

1.2Environmental Factors Affecting wood decay * Nutrient * Extraneous compounds * Temperature * pH * O2 and CO2 concentration

2.0 The Role of microorganisms in wood decay
Deterioration according to the oxford learners’ dictionary means to impair in quality, to degenerate, to weaken or disintegrate; decay. It also means to rot, degradation, perish
Wood is structurally and chemically complex material of living or dead trees. The major constituents of wood are polysaccharides (66-80%) and lignin (19-25%). Angiospemic wood has high content of pentosans while gymnosperm wood in characterized by its high contents of hexosans and lignins (Table 2a). Several mono, di- and oligosaccharides are also found in non-polymerized form in wood while, cellulose exists partly as crystalline and non-crystalline form making microfibrils. The space between fibrils is filled with hemicelluloses and lignin. These principal substrates of wood are susceptible to attack of microorganisms.
Table 2a: Composition of wood (Prof. P.C. Jain Department of Applied Microbiology & Biotechnology Dr. Harisingh Gour University Sagar- 470 003 (M.P.) 02-Jan-2006 (Revised 14-Feb-2008)) | Softwoods | Hardwoods | Polysaccharides | 66-72 | 74-80 | Lignin | 24-30 | 19-25 | Extractives | 2-9 | 2-5 | Ash | 0.2-0.6 | 0.2-0.6 |

3.0 Microbiological degradation of wood
The woods under uninjured bark of healthy trees are generally free from microorganisms. Microbial degradation of wood can cause undesirable changes in colour, lustre, texture, odor, grains and structural integrity of wood thus causing huge loss by destroying wood in forest and wood used in buildings, houses etc. The disease causing microbes alone are responsible for losses amounting more than 65% of the wood volume in forest. Microbes that degrade wood produce extracellular enzymes that breakdown woody cell wall. Different kinds of microorganisms are involved in degradation of wood. Growth characteristics of microorganisms in the wood and type of degradative system results in different decay patterns. During the process of degradation, substrate changes continuously and results in successive change in the microbial population.
Microorganisms found to colonize and degrade wood include (a) Basidiomycetes (b) Ascomycetes (c) Phycomycetes (d) Deuteromycetes and (e) Bacteria. The chemical and structural effects of the attack on wood and resulting decay patterns can be correlated with these groups of microorganisms. The greatest loss of wood however, are due to the basidiomycetous members of families Polysporaceae, Thelophoraceae and Agaricaceae. Many a times interaction between insect and microorganism plays a crucial role in wood decay. Mechanical destruction by insects render wood exposed for action of microbes. Some insects are ectosymbionts with fungi and some termites prefer to colonize on wood attacked by fungi.
Many wood degrading fungi feed exclusively on intracellular contents whilst others continue to decompose components of cell wall as well. This is mainly dependent upon the hydrolytic efficiency based on enzyme secretion. Wood decaying microorganisms can therefore be grouped broadly into:
(I) Microorganisms utilizing cell contents- (but not degrading lignified cell walls)
a. Moulds
b. Blue stain fungi.
(II) Microorganisms that breakdown lignified cell walls:
(i) With limited degradation ability
(c) Bacteria (d) Soft rot fungi
(ii) Microorganisms with high degradation ability:
(e) Brown rot fungi (f) White rot fungi.
3.1 Wood decaying fungi
Moulds belonging to Ascomycetes and Deuteromycetes mainly feed on dead cell contents and their hyphae accumulate in ray parenchyma cells or in cell lumina after penetrating pit-tori. The infestation resembles incipient soft rot. Many members of these classes cause discoloration of wood due to their pigmented hyphae (Blue stain fungi). These are common in softwoods but hardwoods are no exception. Initially their hyphae grow in ray parenchyma cells occurring only rarely in trachieds. In hardwoods the hyphae are also found in fibres and trachieds around the rays. Alternaria, Bispora, Chloridium and Bhialophora spp. are some common bluing fungi. Important wood deteriorating fungi and their effects on wood is given in Table 2 (b).
3.1.1 Soft rot
Fungal attack on the lignified cell walls characterized by a soft decayed surface of wood in contact with excessive moisture is called as soft rot. This type of degradation is caused by fungi belonging to Ascomycetes and Deuteromycetes that can cause limited enzymatic degradation of wood. These fungi principally attack carbohydrates mainly cellulose while lignin is modified or degraded to lesser extent. Characteristically, the hyphae penetrates into the cell wall and develop within S2 layer causing regular and rhomboidal or long cylindrical cavities with conically tapered ends. In early stages, soft rot fungi primarily penetrates through pits and often cause exhaustion of storage materials in the cells, borehole formation begins both on radial or tangential walls. In hardwood, the fungus may also attack the cell walls of the lumen, causing corrosion and subsequent lysis of S3 and S2 layers . In softwood S3 layer being resistant, the principal location of soft rot cavities is the S2 layer. Before invasion of the tracheid cell walls, the longitudinal hyphae in cell lumina branch laterally and produce fine, hyaline, perforation hyphae which grow horizontally through the S3 layer into S2 layer. Later, the hyphae branch into T-shape giving two branches parallel to microfibrils, which grow at the same rate in opposite directions and continue to follow spiral fribrillar structure. Cavity formation is closely related to hyphal growth due to proximity of hydrolases. Apart from fungal species, the pattern of cavities is also influenced by physiological factors e.g. temperature, water content etc. Finally, the entire secondary wall becomes perforated by confluent cavities leaving a collapsible middle lamella, thus causing severe loss in strength. About 70 species of the genera Chaetomium, Sordaria, Peziza, Conithyrium, Cytospora, Phoma, Pestalotia, Chephalosporium, Monosporium, Penicillium, Alternaria, Bispora, Chloridium, Phialophora, Stemphylium, Torula, Graphium, Stilbella, Doratomyces and Fusarium are capable of causing soft rot in different kinds of wood. The attack of exclusive soft-rot fungi is evidenced under extreme moisture conditions. These being the pioneers on newly exposed wood are followed by other group of fungi. A slow attack advancing inward after destruction of outer wood layers, exclusive degradation of polysaccharides (lignin remains intact), formation of chains of cavities in the S2 layers of tracheids and fibres are identifying features of soft-rot. Table 2(b): Wood deteriorating fungi and their effect on wood Basidiomycotina | Amyloporia xantha | Brown rot | Serpula lacrimans | Brown rot ‘dry rot’ in interior timbers in temperate climates | Armillaria spp. | White rot, tree pathogen, decay damp felled timber, spreads by rhizomorphs | Coriolus versicolor | White rot, decay of felled hardwoods | Pleurotus ostreatus | White rot, decay of stored wood pathogen of deciduous trees | Lentinus lepideus | Brown rot, decays wood in contact with the soil | Phlebia gigantea | Brown rot, decays felled pine logs | Coniphora puteana | Brown rot, decays building timbers and wood in ground contact | Stereum sanguinolentum | Brown rot, tree pathogen, decays dead stumps, logs of conifers | Gloeophyllum trabeum | Brown rot, prevalent in exterior woodwork | Ascomycotina: | Chaetomium globosum | Soft rot decays wood in ground contact | Ceratocystis pilifera | Sap stain, blue stain and soft rot in wood chip | Deuteromycotina: | Phialophora fastigiata | Soft rot, decays wood chips, stain wood | Trichoderma viride | Surface mould, early coloniser of freshly cut timber and wood inground ground contact | Cladosporium spp. | Surface mould, ubiquitous, early coloniser of timber | Penicillium spp. | Surface mould, ubiquitous, early coloniser of timber | Aureobasidium pullulans | Sap stain, common blue stain fungus |

This kind of wood degradation is caused via polysaccharides and is characterized by rapid enzymatic hydrolysis of polysaccharides (cellulose) of the cell wall while lignin remains intact. Considerable loss in the wood strength occurs very early in the decay process, often before decay is visually evident. The breakdown of cellulose occurs in a diffused manner through the entire cell wall. Fig. 1 shows severely degraded cell walls caused by a brown rot fungus. Initially thefungal hyphae are concentrated in rays and after depletion of nutrient they are spread into tracheids by destroying the pit-tori and penetration of cell wall. The perforations between cell walls expand in the later stages, leaving large openings between cells. Another character of brown-rot degradation is random cell wall decomposition occuring in patches. The cellulose degradation is well advanced in a group of cells while adjacent cells are slightly affected. This gives a cubically cracked appearance to brown-rot group including genus Polyporus , Coniphora, Coriolellus and Serpulla. Brown-rot fungi cause decay in living trees, timber and wood used in buildings resulting in large losses of strength. This can be hazardous since wood may fail in service. Brown- rot is also referred as dry-rot.

Fig.1 picture obtained from (Prof. P.C. Jain Department of Applied Microbiology & Biotechnology
Dr. Harisingh Gour University)
3.1.2White rot
White-rot causing fungi degrade all cell wall components including lignin and belong mainly to Basidiomycetes. They have exceptional ability to degrade and utilize lignin. In hardwoods, the hyphae of white-rot fungi first colonize the rays and vessels extensively and enter the fibres in later stages. The fungus attacks lignified tissues from the ray cells and vessels or by horizontal penetration of the cell walls. Cell wall penetration is supported by hydrolases liberated at the hyphal tips and lateral surfaces resulting in to wide perforation at later stages. Deepening and coalescing, lysis furrows are produced along the hyphae. In advanced stages, cavities inside the secondary cell walls are also seen. Characteristically, white-rot attack results in gradual thinning of the cell walls both in hardwoods and softwoods. Fig. 2 shows a cross section of an Oak tree with white rot. The fungus has attacked all cell wall components and decayed the wood. Chemical and micromorphological analyses suggest extensive degradation of cell wall component and subsequent utilization of products by white-rot fungi. They are common parasites of heartwood in living trees and are aggressive decomposers of woody debris in forest.
3.1.3 Bacteria
Wood degradation by bacteria is a slow process but it makes a significant part in continuous decomposition process of the wood. Bacteria mainly attack parenchyma cell of the rays and accumulate in resin ducts and parenchymatous tissues. The walls of parenchyma cells may also be attacked and destroyed, however, tracheids and fibres are usually not affected. Bacterial attack has been found to establish on wood after its long and constant exposure to high moisture. It appears as random patches on the surface and inside the wood it develops very slowly and often found as mixed infection with fungi.
Fig. 2 cross section of an oak tree showing white rot (picture gotten from Prof. P.C. Jain, Department of Applied Microbiology & Biotechnology ,Dr. Harisingh Gour University) 3.2 Mechanism of wood deterioration
Microbial susceptibility of wood depends on various characteristics of the lignocellulosic materials. About 40-50% of the dry matter of woody cell walls consist of cellulose, and remaining consists of hemicellulose and lignin, whose types and amount vary within the timber groups. In hardwoods hemicelluloses are mainly xylans, lignin accounts for 21% (European beach). In soft woods mannans dominate, lignin amounts to about 27% (Scot pine). With respect to microbial nutrients, other wood components such as pectin, starch, sugar, proteins, minerals and accessory compounds are of lesser importance. Among these, carbohydrates and proteins generally enhance microbial activity whereas accessory compounds mainly inhibit. Among the 3 main cell wall components cellulose, hemicellulose and lignin, the hemicellulose are most susceptible to microbial attack.

3.2.1 Degradation of hemicelluloses
As an example, European beech wood consists of O-acetyl-4 -O-methylglucuronoxylan. It is a linear chain of about 200 xylopyranose units linked by β (1-4) glycosidic bonds. About 60 - 70 % xylose units have acetyl groups and on an average about 1/10 of its xylanopyranose units have a side chains of 4-O-methylglucuronic acid. Four groups of xylanolytic enzymes are involved in the hydrolysis of 4-O-methlyglucuronoxylan. Endo-β-1,4-xylanases split the xylan polymer randomly into monomeric, dimeric and trimeric xylan fragments of which some are 4-O-methylglucuronoxylotriose. Another enzyme named as exo-β-1,4-xylanosidases cut xylose from the non-reducing end of oligomers. Enzyme α-glucuronidase splits off 4-O-methylglucuronic acid and acetylxylanesterase cuts the acetyl groups and accordingly total enzymic hydrolysis can be achieved.

Fig.3 Picture obtained from ( Prof. P.C. Jain, Department of Applied Microbiology & Biotechnology, Dr. Harisingh Gour University)

3.2.2 Degradation of lignin
Lignin degradation has been investigated mainly with white rot basidiomycetous fungus, Phanerochaete chrysosporium ( Imperfect state - Sporotrichum pulverulentum). The lignin substrates are bound to fungal mycelium and enzymes act on the surface of the polymeric lignin. The important enzyme reaction comprise Cα-oxidation and cleavage between Cα and Cβ by an extracellularly acting H2O2 requiring oxigenase. Demethylations are caused by mono-oxigenases and ortho-ring fission by dioxigenases. Further enzymes, such as laccase and cellobiase, quinone oxidoreductase are involved indirectly but necessarily.

3.2.3 Cellulose degradation
Degradation of cellulose is caused by various kinds of microorganisms including fungi, bacteria and actinomycetes which attack cellulose derivatives. Only a few are known to attack cotton and crystalline cellulose. Like hemicelluloses, cellulose in woody cell walls is generally degraded only by wood rotters and by other microorganisms only after substrate modification / pretreatment.
In wood, cellulose depolymerization by brown rot fungi requires a pre-celluloytic phase which makes cellulose fibers accessible to cellulases, this agent may be Fe2+ / H2O2. Removing hemicelluloses also increases cellulose degradation. A scheme of enzymic hydrolysis of cellulose is given in Fig. 4 which indicates the involvement of numerous cellulolytic enzymes in cellulose degradation. These enzymes act synergistically and depend on the primary attack by endo-cellulase of carboxymethylcellulase (CMCase) type on the native cellulose molecule producing crystalline cellulose. These are further attacked by exo- and endo-cellulases of avicelase type. Accordingly a number of cellobiose and cellodextrins are produced which are further attacked by endo-cellulase and exo- cellulase (CMCase type) and cellobiase (β- glucosidase) enzymes resulting in formation of glucose (complete hydrolysis of native cellulose).

Fig.4 picture obtained from (Prof. P.C. Jain, Department of Applied Microbiology & Biotechnology,
Dr. Harisingh Gour University)

4.0CASE STUDY
Pleurotus ostreatus
Kingdom: Fungi
Phylum: Basidiomycota
Class: Agaricomycetes
Order: Agaricales
Family: Pleurotaceae
Genus: Pleurotus
Species: P. ostreatus
Pleurotus ostreatus, the oyster mushroom, is a common edible mushroom. It was first cultivated in Germany as a subsistence measure during World War I[Eger, G., Eden, G. & Wissig,E. (1976)] and is now grown commercially around the world for food. However, the first documented cultivation was by Kaufert.[ Kaufert, F. (1936)] There is some question about the name Pleurotus corticatus, but no question that he cultivated an oyster mushroom. It is related to the similarly cultivated "king oyster mushroom". Oyster mushrooms can also be used industrially for mycoremediation purposes. The oyster mushroom may be considered a medicinal mushroom, since it contains statins such as lovastatin which work to reduce cholesterol.[ .[ Kaufert, F. (1936) ]

The oyster mushroom is one of the more commonly sought wild mushrooms, though it can also be cultivated on straw and other media. It often has the scent of anise due to the presence of benzaldehyde (which, however, smells more like almonds).[ Beltran-Garcia, Miguel J.; Estarron-Espinosa, Mirna; Ogura, Tetsuya (1997)]

Fig.5 picture obtained from Wikipedia
The oyster mushroom is widespread in many temperate and subtropical forests throughout the world, although it is absent from the Pacific Northwest of North America, being replaced by P. pulmonarius and P. populinus.[ Trudell, S.; Ammirati, J. (2009)] It is a saprotroph that acts as a primary decomposer of wood, especially deciduous trees, and beech trees in particular.[ Phillips, Roger (2006)] It is a white-rot wood-decay fungus.

The oyster mushroom is one of the few known carnivorous mushrooms. Its mycelia can kill and digest nematodes, which is believed to be a way in which the mushroom obtains nitrogen. The standard oyster mushroom can grow in many places, but some other related species, such as the branched oyster mushroom, grow only on trees.
While this mushroom is often seen growing on dying hardwood trees, it only appears to be acting parasitically. As the tree dies of other causes, P. ostreatus grows on the rapidly increasing mass of dead and dying wood. They actually benefit the forest by decomposing the dead wood, returning vital elements and minerals to the ecosystem in a form usable to other plants and organisms. Pleurotus ostreatus produces the cellulolytic and hemicellulolytic enzymes endo-1,4-β-glucanase, exo-1,4-β-glucanase, 1,4-β-glucosidase, endo-1,4-β-xylanase, 1,4-β-xylosidase, endo-1,4-β-mannanase and 1,4-β-mannosidase and ligninolytic enzymes Mn-peroxidase and laccase during growth on wood in the presence and absence of Cu, Mn, Pb, and Zn.
5.0 Control of wood deterioration
Several factors can be manipulated artificially for control and prevention of wood decay. Reduction in moisture content of wood (below 20%) and storing wood at relative humidity levels below 60% or storage under high osmotic pressure (using high concentrations of salt or sugar) and significant reduction in pH by allowing natural acid fermentation can be used as preventive measures to control microbial spoilage of wood. Further, the wood can be sterilized by heat or radiation and can be coated with impervious or biocidal coating. Logs are often stored in ponds to protect against fungal attack, prevent drying and splitting of ends. During shipment the moisture content should be reduced to safe moisture level. An ideal wod preservative (fixed or leachable) should be sufficiently toxic at low concentrations, capable of penetrating timber, non-deteriorating for wood, non-flammable and cost effective. These can be water based, tar oils, organic solvent based or emulsions of organic preservatives. A fixed preservative reacts with cell walls of wood and converts the active ingredient to an insoluble compound which is resistant to leaching. For example chromate, copper and arsenic (CCA) treated wood leads to their impregnation, which provides prolonged protection. Leachable preservatives (eg. sodium octoborate) do not become fixed and are applied by diffusion process. Woods under prolonged exposure of weather (telephone poles, railway sleepers, fence posts etc.) can be preserved by creosote distillate from coal tar.
Some commonly used preservatives are copper and zinc naphthamates, pentachlorophenol, tri-n-butyl tin oxide and methyl bisthiocyanate. In addition gamma - BHC, an insectiside, is also used to provide protection against insects. Preservatives can be applied for in-situ protection by brushing, spraying or drenching. On the other hand, wood is immersed in preservatives for periods ranging upto one week depending upon thickness of material and desired penetration. For impregnation, timber is pushed into steel cylinder containing preservative and closed with a pressure door. The cylinder is evacuated and the preservative is forced into the pores of wood by pressure. Other controls include;

1. Select and grow only species and varieties or cultivars of shade, ornamental and fruit trees and shrubs that are well adapted to the area. Plant only vigorous, disease-free nursery stock. Grow somewhat tender species in sheltered locations. Plant at the proper depth in a large hole, well spaced apart, in fertile, well-drained soil of the proper soil reaction (pH).
2. When feasible, keep woody plants vigorous through (a) proper applications of fertilizer in mid- to late-autumn or early spring; (b) thorough soaking of the soil to a 12-inch depth every 10 to 14 days during extended hot, dry periods; and (c) wrapping the trunks of newly transplanted, thin barked trees with sisalkraft paper, special tree-wrapping paper, or other appropriate material prior to winter.
3. Prune periodically to remove all dead, dying, interfering, and broken branches so that they are nearly flush with a major branch or main stem; leave the "collar" that surrounds the base of the branch.
Prune broken stems below the damaged portion so that water will drain off and not collect on the wound surface. The severed ends of roots should be made blunt rather than left jagged. Pruning is best done during the dormant season when the weather is dry. Pruning in late spring often leads to separation of wood and bark around pruning wounds.
4. Avoid burning of trash near trees and shrubs.
5. Make as few changes as possible in the soil grade or drainage patterns in the vicinity of trees. Avoid compacting soil over the roots.
6. Follow cultural practices suggested by Extension horticulturists and foresters at the University of
Illinois at Urbana. Your local Extension office and a professional arborist or forester can also provide valuable help on general tree care.
7. Control insect borers by spraying the trunk and major branches with a suggested insecticide following recommendations of University of Illinois Extension entomologists. Many wood boring insects infest trees previously weakened by drought, temperature extremes, various diseases, and so forth. 8. Avoid all unnecessary bark wounds. When bark and wood injuries do occur, treat them promptly.
Cut away all loose or discolored bark. Remove splintered wood. Clean, shape, and smooth the wound into a streamlined oval or vertical ellipse. Then swab the surface liberally with an antiseptic such as 70 percent alcohol or shellac. The use of a commercial tree wound dressing (tree paint) is of questionable value since it does NOT check the invasion of wood by decay fungi. The barrier zone of cells formed by the cambium effectively confines the decay within the tissues present at the time the tree was wounded. The use of tree wound dressings is largely cosmetic and their usefulness in preventing wood decay is questionable.
9. Reduce losses in forests, plantations, and farm woodlots by (a) eliminating, as much as possible, the introduction of wood-rotting fungi into healthy stands by early pruning of lower branches; (b) conducting logging and thinning operations to minimize breakage of branches and the creation of major wounds (top breaking, stripping of bark, butt and trunk damage from heavy equipment) to the stems and roots of the remaining trees (such operations should take place during the dry season or winter to avoid much of the mechanical damage to the root systems of the living trees that remain;
(c) harvesting trees before they become overly mature and thus increasingly susceptible to woodrotting fungi; and (d) not letting livestock graze in farm woodlots. Livestock damage trees through soil compaction, butt damage, and root wounds caused by sharp hoofs. All trees that are dead, hazardous, diseased, or pest ridden should be removed.
10. Control discoloration and decay in lumber and other wood products by drying the wood in a kiln or by treating with a recommended wood-preserving fungicide. Wood likely to be in contact with soil or moist surface should be treated with a wood preservative.

5.1 CONCLUSION
From various research and hypothesis, it can be said that wood being the processed part of trees have indigenous microorganisms and some of these microorganisms serve as normal micro flora which could in turn due to environmental conditions become opportunistic and cause decay and diseases which might affect the wood. If you can figure out the mechanism of interaction, invasion, and destruction, you could TAILOR the treatment, remedies based on your understanding of concepts for blocking/ arresting the progress of invading pathogenic elements from our arsenal of bioresources. This would produce indigenous biopesticides, fungicides, insecticides, thereby boosting crop production in our humble attempt to meet VISION 20; 20; 20.

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* Kaufert, F. (1936) The biology of Pleurotus corticatus Fries. Minnesota Agricultural Experiment Station Bulletin 114. * Beltran-Garcia, Miguel J.; Estarron-Espinosa, Mirna; Ogura, Tetsuya (1997). "Volatile Compounds Secreted by the Oyster Mushroom (Pleurotus ostreatus)and Their Antibacterial Activities".

* Trudell, S.; Ammirati, J. (2009). Mushrooms of the Pacific Northwest. Timber Press Field Guides. Portland, Oregon: Timber Press. p. 134.

* Phillips, Roger (2006), Mushrooms. Pub. McMilan, ISBN 0-330-44237-6. P. 266.

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* Chisholm, Hugh, ed. (1911). "Alburnum". Encyclopædia Britannica (11th ed.). Cambridge University Press.

* Mimms, Agneta; Michael J. Kuckurek, Jef A. Pyiatte, Elizabeth E. Wright (1993). Kraft Pulping. A Compilation of Notes. TAPPI Press. pp. 6–7. ISBN 0-89852-322-2.

* Christina Bienhold; Petra Pop Ristova; Frank Wenzhöfer; Thorsten Dittmar; Antje Boetius (January 2, 2013). "How Deep-Sea Wood Falls Sustain Chemosynthetic Life". PLOS ONE.

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