Dehumidifier Kiln Drying and Insects

Cooler temperatures in a DH kiln aren't a reliable way to kill all insects, but the dryness will get some of them. May 18, 2010

I have read in other posts that you need a high kiln temperature to kill insects such as powder post beetles. I have a dh kiln that I only run up to around 105 degrees. I have seen evidence of pp beetles in stickered lumber prior to kiln drying but have never seen any post drying. Wouldn't the fact that you are bringing moisture content down to around 6% kill insects through desiccation?

Forum Responses
(Sawing and Drying Forum)
From contributor B:
Short answer is no. We also run a DH kiln (Nyle L200), and run the temp up to 140 F for four hours to sterilize our lumber prior to removing from the kiln. Are you following a certain KD schedule that has you stop increasing temp at 105? Curious as 105 degrees isn't a set point for our temp during any schedules for group I, II, or III. Irregardless, in the event that your kiln won't reach this temp - check the archives, lots of discussions about not only KD to sterilized, but also adding auxiliary heat to reach sterilizing temps in kilns that weren't capable.

From the original questioner:
I am pretty low tech in my lumber drying. My schedule consists of monitoring the water that comes out of the kiln on a daily basis and increasing the temperature, as needed, to keep the water coming out. I never have to go over 105 degrees to get down to 6-8% moisture. The 105 degrees is just my number. I guess the kiln will go to a higher temp but I am with the understanding that the lower the temperature, the better the end result in lumber quality. I have an Ebac DH that I have been using around 20 years and have always had good results - no checks or other defects. I noticed what appears to be powder post beetles - little piles of wood dust - on some stickered air dried red oak I put in the kiln this weekend. I am just concerned about any long term damage to the wood.

From contributor B:
Sounds like great results from your kiln. We've always had good luck sticking to the sterilization procedure described. For 25% to final MC, the kiln is usually running at 120 F. I always wondered if that was enough to sterilize - but everything we've ever been told says you have to get the core higher to be sure. I just can't chance selling lumber, or worse yet a finished product like hardwood flooring that isn't free of critters!

From Gene Wengert, forum technical advisor:
If one notices an insect in wetter lumber, chances are that it is not the lyctid PPB that inhabits dry wood. Rather what is seen is an insect that likes greener wood, so it will die when the wood is dry. Also, the lyctid PPB takes some time after the eggs are laid for the insects to emerge from the wood, so insects seen in green drying wood would not be the lyctid PPB. The wood can be heated in another chamber to 130 to sterilize the wood at that point. Of course, exposure of wood to the PPB later (after drying) can result in infection.