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Wood-rotting fungi
(revision date: 7/14/2015)
Use Integrated Pest Management (IPM) for successful pest management.
Biology
In the Pacific Northwest, fungal organisms are the primary cause of wood decay. Wood-rotting fungi require moisture which can result from inadequate ventilation, faulty plumbing, and roof leaks, as well as splashing from improperly maintained gutters or downspouts or direct wood-to-ground contact. There are several types of wood-rotting fungi, including brown rot, soft rot, and white rot. BROWN ROT damage is more common on softwoods, such as fir, hemlock, pine, etc. It causes severe weakening of the wood. At advanced stages of decay, the wood appears as a darker brown, dry and fragile crumbly mass. There are numerous cross-grain breaks that give a “cube-like” appearance to the wood fragments. Sometimes brown rot is incorrectly referred to as “dry rot,” even though moisture is required for decay. SOFT ROT fungi also cause wood to lose significant strength early in their attack. However, they typically attack from the surface inward and are more common where the wood is prone to frequent wetting. They are slower-growing than brown and white rots. Otherwise, the differences between brown rot and soft rot may be difficult to distinguish. WHITE ROT fungi are most prevalent on hardwoods (wood from deciduous trees). In advanced stages, the decay appears as a bleached, whitish, spongy or stringy area. Extensively damaged wood loses most of its weight and strength. By the time the disease can be detected visually significant weakening has occurred. Other species of fungi cause mold growth or staining on wood. While those organisms are indicators of excessive moisture, they are less of a concern in terms of structural damage. In addition to damage by wood-rotting fungi, damp or rotting wood may also be attacked by other organisms including moisture ants and dampwood termites, both of which accelerate the decay process.
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Management Options
Non-Chemical Management
- Correct or prevent conditions that result in wet wood.
- Repair leaky plumbing and drains.
- Install effective gutters, downspouts, roof overhangs, etc. Repair or replace leaky or poorly functioning gutters and downspouts. Be sure that downspouts direct water flow away from the structure.
- Repair roof damage and leaks.
- Prevent or correct wood-to-ground contact, particularly any contact involving structural components.
- Provide adequate ventilation, especially beneath structures. Your local building code will specify minimum requirements.
Select non-chemical management options as your first choice!
Chemical Management
None recommended. If wood decay problems are suspected, particularly in the supporting structure of a building, you may wish to contact a structural pest inspector or pest management professional.
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