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Sharing a post about Powder Post Beetles

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I read this description on another site, it's written by Dr Gene Wengert. It's a great concise description of the powder post beetle we should worry about:

"As a review, the lyctid powderpost beetle is the only insect that gets into kiln dried or under 15% MC hardwoods.  This insect does not fly around long distances, so you need a source of infection...usually other nearby infected wood or bamboo.  A lot of foreign hardwood is infected.

So, it will rarely, if ever, be found in air-dried wood (too wet), so it is not necessary to sterilize wood in the kiln as the MC was too high when the lumber went into the kiln and there is no source of infection in the kiln.  Any air dried insects, like the ambrosia beetle or anobiid beetle, do not live in wood under 15% MC, so again, sterilization is not necessary in kiln drying.

Once the lumber leaves the kiln, if it is over 8% MC, it could be subject to infection...that is, drying or even sterilization in the kiln process provides no protection after drying, other than low MCs.

The key for identification of the lyctid PPB, in addition to low MC, is that is makes exit holes that are round and 1/32 to 1/16 inch in diameter.  The ambrosia beetle (likes very wet wood) also makes 1/16” diameter holes but because of the moisture differences, it is easy to tell which beetle made the holes.

When the beetles leave the wood, they make the visible holes we see.  Then, mom and pa are looking for each other to breed...they like wood dust and other wood debris, so a clean floor, etc. will help eliminate their breeding ground.  The pregnant female now flies up to the wood and looks for nooks and crannies to lay her eggs.  She has a tiny tube that extends from her body that she sticks down in the crannies.  So, she loves red oak and ash with their cellular openings, but not smooth woods like maple, basswood, etc.  the eggs hatch in a few months and the little worms, called larvae (singular) and larva (plural), then slowly make small tunnels in the wood for the next year...sometimes three years.  When cold, they are inactive.  Finally, one warm day, they convert to a flying insect and burrow their way to the surface and the cycle repeats.  This long life cycle is also useful in identification, as most hardwood insects have several broods per year, which means that other insects will bore to the surface perhaps a month after the insects' eggs were laid.

This cycle length of the lyctid PPB is why it is rare that an infestation will be seen in KD lumber during the first six months after leaving the kiln.  In fact, it is rare the first year after leaving the kiln because the females have to find the grainy wood, lay eggs, have at least 8% MC, and then the larva have to grow for 6 months before they make holes as they leave the wood.

Note that termites leave nuggets or pellets behind, but the PPB leaves very fine dust.  Note that activities of insects in air drying will result in tunnels and sometimes fine dust, but these alone do not indicate an active PPB.  In fact, in KD lumber such past activities are frequently misinterpreted as an active infestation.

So, why should you heat sterilize wood?  Such an activity allows us to positively swear in court that when the lumber left the kiln it was free of viable eggs, and insects.  Any infection later is due to infection later, perhaps in storage.  If the kiln drying storage is clean and has no foreign wood, then it is virtually impossible during a few weeks or months of storage to get the lumber infected...the MC is too low and there are no nearby insects hatching from adjacent lumber.  Any infections occurred after the lumber left the kiln facility.  Even in a solar kiln, without high heat, this conclusion is true, as described in the above paragraphs."

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