Thread: Brown Rot, White Rot and other Wood Pestilence.

When excavation reaches the incipient stage of only discoloration of otherwise sound wood, CPES (an epoxy sealer) may be useful to isolate the remaining spores and reduce the wood’s potential to absorb moisture prior to replacing the structure lost to the rot.

White Rot



Sometimes called “slime” or “wet” rot, the fungus species responsible for White Rot are most often found in non-durable hardwoods where they cause spalting. Here you see large patches of White Rot in a sea of Blue Mold.



Like all fungi, tendrils or hyphae spread the fungus to areas favorable for its growth, these sufficiently large to be obvious.



When they attack softwoods like the Douglas Fir shown here, they don’t seem to penetrate as deeply or as quickly as does Brown Rot and can often be planed off to no ill affect to the use of the wood.



Incipient White Rot on a sapwood edge of roughcut Douglas Fir 2X stock.

Soft Rot

Soft Rot is caused by another group of fungus species and is generally found in telephone poles and other buried posts immediately above ground level. The entire surface of the wood becomes punky and can be lifted off in sheets.

Lichens



Continued….

Interesting and sometimes colorful little algae-fungus combinations that are generally harmless and can be brushed off.

Blue Mold and Ambrosia Beetles

You’ll find Blue Mold (or Blue Stain) without Ambrosia Beetles but you’ll never find Ambrosia Beetles without the stain. Various species of molds and sapwood stains feed off the moist sugars in sapwood and discolor it in the process, often permanently.



Here you can see bluish discoloration in the sapwood edge of a Douglas Fir joist. As the joist was recently scrubbed with full-strength bleach, the stain is permanent. You can also see a few bluish pin holes in the sapwood from Ambrosia Beetles. These insects attack stacked logs and downed trees still having intact bark throughout the warm months of the year within as short a period as two weeks. The adult beetles bore through the bark into the wet sapwood, lay their eggs in the tunnels, and depart. Their secretions plus the sugar in the sapwood attracts Blue Mold development in the tunnels, which their larvae feed on after they hatch and also eventually exit the log to continue the cycle. In some woods the result is considered attractive, and there is a market for “Ambrosia Maple” as one example. Prevention measures include milling immediately in summer, debarking or ponding logs waiting to be milled, including continuous irrigation of the log stacks with water, which also inhibits other fungi due to oxygen depletion.

Carpenter Ants

Carpenter ants come in small and large sizes and also don’t eat wood, but use it for nesting. They require warmth and nearby food – remove one or both to drive them away.



The tiny species don’t have big munchers and seem to only attack wood already softened by fungus, here where a sapwood sticker in a board stack rotted and was attacked by the ants. The photo is of the mostly heartwood board beneath it and you can see where the ants attempted to bore, but only succeeded in a small area of sapwood. These aren’t a big problem here, and the damage can be planed off.



The large species are incredibly tough, can chew their way through almost anything, and here prefer to nest in the pith areas of live cedar trees, often forming centuries-old colonies of vast numbers. In the lumber yard, they usually don’t attack stickered stock through around 4X thickness, because there isn’t enough protection from the cold in relatively thin boards. They don’t usually attack stickered 6X and 8X beams like the one shown either, but if you are sufficiently absentminded to restack them touching each other after grading, you provide 8-12X of insulation and a perfect entry point for the ants. When they infest the wood or insulation in your house, what they are attracted to is the warmth. Sprinkle a persistent insecticide like Diazinon around the outside foundation of your house and beneath your lumber stacks when the temperature reaches 55 degrees in the spring.

Powder Post Beetles



A much more serious pest, the various species of Powder Post (or Furniture) Beetles eat the starch contained in wood instead of just nest in it, and penetrate throughout the heartwood as well as the sapwood. They are common in barn timbers, old furniture once stored in barns, and hardwood stacks overgrown with vegetation that inhibits air flow. One variety even penetrates hard varnish finishes to get to the wood beneath. There are various home remedies of fuming and borates but none are 100% reliable. To eliminate every stage of the beetle, infested wood must be kilned per the “KD-HT” schedule previously discussed.

Preventions are usually easier than cures, but knowing which pests are fatal and which are merely cosmetic helps you pick your battles.

Reference: A.J. Panshin and Carl de Zeeuw, Textbook of Wood Technology 3rd Ed, McGraw-Hill 1970.