Q. How can I identify some insects in my wood?

A. Here is a listing of common, wood inhabiting insects and general information about these insects. Not all the information, including pictures, on the Internet is accurate.

Common Insects

AMBROSIA BEETLE. Other names: Pinworms. Holes: Round, 1/32 inch to 1/16 inch diameter. Preferred species: aspen, cottonwood, elm, hackberry, hickory & pecan, maple, oak, sweet gum, tupelo, yellow-poplar, and pine. Preferred MC: Over 45 percent MC. Misc info: Often starts in the woods; holes often have a small dark ring around them; holes may be cut at an angle when sawing so they appear oval shaped.

ANOBIID BEETLE. Other names: Anobiid powderpost beetle, spotworm. Holes: round, 1/16 inch to 1/8 inch diameter. Preferred species: ash, maple, oak, yellow-poplar; pine and more. Preferred MC: 13 to 30 percent MC at the spot of activity. Misc info: Holes have fine sawdust and also some elongated pellets in them; active almost totally in sapwood.

GRUBS: Holes: Often oval shaped, 3/16 inch in large diameter. Preferred species: Any. Preferred MC: Very wet wood. Misc info: Active only in the tree -- not in lumber; the larva (worm stage of various insects) are called grubs and the holes are called grub holes.

LYCTID POWDERPOST BEETLE. Other names: Powderpost beetle or PPB (confusing as there are other PPB). Holes: round, 1/32 inch to 1/16 inch diameter. Preferred species: Hardwoods only including ash, cherry, hickory-pecan, oak, sycamore. Preferred MC: 8 to 28 percent MC. Misc info: sapwood only, emerge when there is a warming trend; emerge usually 6 to 10 months after eggs were laid; use pine stickers and pine storage buildings to avoid them in storage.

OLD HOUSE BORER: Holes: Oval, with rippled walls, ¼ inch in wide dimension. Preferred MC: under 30 percent MC at point of activity but not too active under 10 percent MC; Preferred species: pine, spruce, fir. Misc info: Very slow in a house, so reproduction is rare; in dry wood it may take three years or more to exit the wood and look for a mate; usually mating is unsuccessful in a house so spreading infestation is rare; jaws make a snap or click sound when taking a bite of wood.

Less Common Insects

CARPENTER ANTS: Holes: Network of various sized cavities. Preferred species: Almost any hardwood or softwood. Preferred MC: Wet, decaying wood over 20 percent MC. Misc info: Activity usually stops when logs are sawn into lumber.

CARPENTER BEES: Holes: Round, 7/16 inch diameter; are clean inside and have right angle turns. Preferred species: white pine and yellow pine. Preferred MC: Under 30 percent MC. Misc info: Holes used for nesting; bees do not eat wood for nourishment unlike other insects; return annually to the same holes; plug holes before they return in the spring; use an approved insecticide on and near the wood.

TERMITES. Other names: Subterranean termites. Holes: Network of tunnels within the wood. Preferred species: Virtually all species.  Preferred MC: under 30 percent MC but sometimes wetter. Misc info: Need a source of water so they make contact with wet soil and build a mud tunnel to connect wet soil with the wood; decay commonly associated with activity; commercial treatment required.

Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 35 years. He is extension specialist emeritus at the University of Wisconsin-Madison.

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