by Steve Sproul California General Contractor #450095
Powderpost beetles are second only to termites in their destruction of wood. The name Powderpost, comes from the extremely fine, flour-like fecal matter, called ³frass² that is pushed out of infested wood by emerging beetles. Because the dust-like powder is lose in the feeding tunnels, it may continue to sift out long after the adults have emerged and after the infestation has died out.
Adult powderpost beetles are small elongated, flattened, reddish-brown to black beetles. They range in length from 1/12 to 1/5 in. They are attracted to light and often can be found on window sills in infested rooms. They are generally brought into buildings on wood that contains their eggs or larvae. They prefer hardwoods such as ash, oak, mahogany, hickory, maple, walnut, bamboo and wicker. In nature they attack only old well
seasoned d wood. Almost all of the attack will occur in the sapwood. Oak firewood, two to four years old, is a common source of infestation in the home. Indoors, Powderpost infestation may be found in hardwood flooring, rough sawn timbers, plywood, barnboards, and hardwood articles, such as tool handles, crating, furniture and picture frames. An infestation begins when the female deposits her eggs in the surface pores of the wood or crawls into old adult emergence holes and deposits her eggs. Eggs hatch within 10 days, and larvae tunnel through sapwood, usually following the grain. Mature larvae are curved wormlike, cream-colored grubs. The larval stage is completed in two to eleven months. As the larvae matures, it chews to within 1/8 in. of the surface of the wood and prepares a small chamber. Adults will emerge two to three weeks later and are commonly seen in April or May. The emergence holes are round, 1/32 to 1/8 in. in diameter and there are large quantities of frass packed at the surface.
Powderpost
beetles will not lay eggs in sap wood with a starch content of less than 3%. They can live in wood with a water content of between 8% and 32%. Because green wood is commonly about 50% water, attacks are generally confined to partially or wholly seasoned wood with a moisture content of 10% to 20%.
Infestations die out on their own as conditions change in the wood. Over time, the starch contend in sap wood will naturally decline, so the wood becomes less susceptible to attack. The most seriously damaged structures are unheated buildings, which tend to have increased moisture and humidity.
Controlling Powderpost beetles-There are four methods of control. If the infested wood can be easily removed- one piece of oak baseboard or flooring, for instance, this would be the preferred method. Small articles such as antique tools or a picture frame may be heated in a kiln or placed in a freezer where rapid temperature change does most of the killing. If the infestation is widespread, fumigating may be called for. Methyl bromide is the preferred chemical because it will kill all stages of life including the eggs. Fumigation will kill all insects present, but will do nothing to prevent future infestations.
Painting/sealing the wood will help prevent it from becoming infested if all pores are plugged, but it will not control insects already in the wood. Adult females will use existing exit holes to get back into the wood and find pore spaces to lay their eggs.
The final treatment alternative is to spray the surface of the infested wood with insecticide. By placing a thin layer on the
outer surface, adult females will come in contact with the treatment will be killed, but any larvae living deep in the wood will not be affected. This surface treatment helps to prevent reinfestation and over time will thin out populations. The infestation will remain active for some time after treatment, and even if the adults are killed upon emerging they still produce exit holes.
Proper coverage is of great concern with the surface treatment. Spraying the top surface of flooring or the outer surface of baseboards still leaves the underside untreated and gives the beetles continued access to the wood.
Contact: Steve Sproul General Contractor CA lic.#450095 707-953-1708
Comments or Questions (I'll give you the straight stuff!)
stevesproul@comcast.net
11/10/2009
/BODY
