In order to efficiently maintain wood-based structures, wood pilings, and combat wood decay. It is important to know what you possibly could be up against.
The most common and invasive marine borers are Teredo, Bankia, also known as Shipworms, and Limnoria more commonly known as Gribble. The origin of Shipworms is not exactly known. However, the earliest known infestations date back to Europe and Christopher Columbus. Present day it is a globally invasive in any habitable environment.
Teredo Navalis – Although it may look it, it is not actually a worm but a saltwater clam. It’s a highly specialized bivalve mollusk adapted for boring into and living in submerged wood. It uses its sculpted shell to rasp the wood particles. As they bore through the wood they leave behind calcareous lined tubes. These tubes cause lumber to be unsuitable or structures to be weakened.
Bankia Setacea – Commonly found in U.S. South Atlantic. The larvae settle onto wood pilings, logs, and structures. As the larvae mature, they begin to bore into the wood. If gone untreated and the infestation is allowed to grow. It will leave the wood honeycombed causing it to become structurally unstable. Similar to Teredo Navalis they also favor salt and brackish water.
Honeycombed Wood (UBC Forestry)
Limnoria – The crustacean species burrows just below the wood’s surface creating tunnel networks within. The tripunctata species is most notable because it can still attack creosote treated wood.
Solutions – Use hardwoods that are naturally resistant to rot and permeation. Treat others that are not as resistant such as softwoods with a preservation.
Fungi are destructive lower plant forms which require a supply of air, warmth, food, and moisture to thrive. Sections of constructional wood at the water line which are alternately wet and dry are the most susceptible to fungi attack.
Mold – More so found on the surface of material. It is generally easily removable by planing or brushing. Most often if mold is present, it is breeding ground for bacteria decay.
Sapstain (Sapwood) – This fungus deeply penetrates through the wood. The wood strength is not affected but it’s resistance to shock may be highly reduced. Signs of Sap Stain fungi are discolorations such as brownish, blue, black, or gray.
Solution: Advised ways to combat sapstain is to ensure the timber is quickly processed. Additionally, treat the wood with an anti-sapstain preservative. Treating the wood when cut prevents the fungi from forming. During this time is when the wood is most susceptible to sapstain fungi.
Brown Rot – Causes wood to crack across the grain, shrink, and collapse. Since the rotting pattern is asymmetrical this causes the wood to be fail along the cracks.
White Rot – The wood does not crack but once it is severely degraded the wood structure will fail.
Soft Rot – Soft rot fungi can tolerate wetter and drier conditions than the more familiar decay fungi. The depth of attachment is shallower. The change from decayed area to undamaged area is rapid. It is typically responsible for the surface weathering of wood.
Solution – Use hardwoods that are naturally resistant to fungal. Softwoods can be used as long as they are treated with an anti-fungal preservative. Additionally, ensuring design and construction techniques that provide quick drainage and water management of wood waterfront structures will help minimize damage from rot.