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WOOD BORING BEETLES

Wood boring beetles can be very destructive to structures. There are many wood boring beetles, but we are concerned with only those that may be found inside structures. There are several identifying characteristics that will help in determining which beetle is infesting wood. Beetles tend to enter wood by the adult laying eggs in crevices. The larvae enter the wood and feed on the starch content within the wood. They pupate into adult beetle. These adult beetles will burrow out of the wood, leaving an exit hole. This exit hole is the first characteristic that we will look at. Other characteristics are the type of wood, the age of the wood, and the appearance of the frass (sawdust or powdery material found in or near the damaged wood).

AMBROSIA BEETLES

  • SHAPE OF EXIT HOLE: Round
  • SIZE OF EXIT HOLE (inches): 1/50 to 1/8
  • WOOD TYPE: Soft and Hardwoods
  • AGE OF WOOD: New
  • FRASS: None Present
  • COMMENTS: Ambrosia beetles feed only on Ambrosia fungus which grow in moist, usually green wood. The beetles introduce the spores into their galleries, and wherever the fungus grows, the wood is stained blue, black or dark brown. These stains are the identifying characteristics for this type of beetle. Since they tend to infest green wood, they are not considered a re-infesting type beetle, requiring no treatment.

LYCTID BEETLES

  • SHAPE OF EXIT HOLE: Round
  • SIZE OF EXIT HOLE (inches): 1/32 to 1/16
  • WOOD TYPE: Hardwood
  • AGE OF WOOD: New and Old
  • FRASS: Fine, flour-like, loosely packed
  • COMMENTS: These beetles, known as true powder post beetles, leave behind very fine powdery frass with no pellets. These are the most common of the re-infesting structural beetles.

BARK BEETLES

  • SHAPE OF EXIT HOLE: Round
  • SIZE OF EXIT HOLE (inches): 1/16 to 1/32
  • WOOD TYPE: Bark / Sapwood interface
  • AGE OF WOOD: New
  • FRASS: Fine to coarse, bark colored, tightly packed
  • COMMENTS: As their name implies, these beetles infest behind the bark of lumber. This becomes a problem only if the bark is left on the wood as in log cabins and certain types of furniture. This beetle is not a re-infesting type beetle

ANOBIID BEETLES

  • SHAPE OF EXIT HOLE: Round
  • SIZE OF EXIT HOLE (inches): 1/16 to 1/8
  • WOOD TYPE: Softwood and Hardwood
  • AGE OF WOOD: New and Old
  • FRASS: Find powder and pellets, loosely packed. Pellets may be absent and frass tightly packed in some hardwoods.
  • COMMENTS: The two major types of these beetles are called the Furniture Beetle and the Deathwatch Beetle. Although the Furniture Beetle infests mainly furniture, it may also infest wood members of the house. The Deathwatch Beetle is named for the clicking sound it makes (a mating call) which can be heard in the still of the night. The deathwatch name came from when a person was dying and the house was still and quiet, the beetle clicking sound was heard.

BOSTRICHID BEETLES

  • SHAPE OF EXIT HOLE: Round
  • SIZE OF EXIT HOLE (inches): 3/32 to 9/32
  • WOOD TYPE: Soft and Hardwood
  • AGE OF WOOD: New
  • FRASS: Fine to coarse powder, tightly packed
  • COMMENTS: These beetles rarely re-infest wood inside a structure.

ROUND HEADED BORER

  • SHAPE OF EXIT HOLE: Round - Oval
  • SIZE OF EXIT HOLE (inches): 1/8 to 3/8
  • WOOD TYPE: Soft and Hardwoods
  • AGE OF WOOD: New
  • FRASS: Coarse to fibrous, mostly absent
  • COMMENTS: These beetles do not re-infest wood inside a structure. Occasionally, these beetles can be found inside. Their source is mostly likely infested firewood.

FLAT HEADED BORER

  • SHAPE OF EXIT HOLE: Oval
  • SIZE OF EXIT HOLE (inches): 1/8 to 1/2
  • WOOD TYPE: Soft and Hardwoods
  • AGE OF WOOD: New
  • FRASS: Sawdust-like, tightly packed
  • COMMENTS: This beetle does not re-infest the wood inside structures

OLD HOUSE BORER

  • SHAPE OF EXIT HOLE: Oval
  • SIZE OF EXIT HOLE (inches): 1/4 to 3/8
  • WOOD TYPE: Softwoods
  • AGE OF WOOD: New and Old
  • FRASS: Very fine powder and tiny pellets, tightly packed
  • COMMENTS: The life cycle of this beetle can last from 3 to 12 years. Because this is such a long period of time, considerably damage can be done before the beetle is noticed, because of the few number of exit holes does not reflect actual damage inside the wood.

TREATMENTS FOR WOOD BORING BEETLES

The treatment for re-infesting wood boring beetles tends to be the same for all the beetles. There tends to be two types of remedies for these beetles.
NON-CHEMICAL solutions revolve around the reduction of moisture in the wood. Re-infesting beetles require a minimum of 20% moisture content for them to re-infest the wood. If the moisture level can be reduced, then the beetle may just leave the structure. See MOISTURE CONTROL.
CHEMICAL solutions usually involve treating the infested wood with a borate solution, usually BoraCare or Timbor, both restricted pesticides. Therefore, you will need to hire a pest management professional for this. Occasionally, with excessive infestations, a structural fumigation may be required.
Even if a chemical treatment is pursued, the reduction of the moisture content in the wood should also be pursued.

If you have any questions, please ask Pestdude!

Also see the following links:
PESTICIDES
CHOOSING A PEST MANAGEMENT PROFESSIONAL