I have a technical question that I have been unable to find an answer for...Does a vacuum drying process, such as use in I Dry, using similar vacuum pressure and temperatures, kill the lyctid powderpost beetle (eggs, larva, pupa, and insect? I would like to have an original citation for any tests that have been done....English, German, or whatever language.
Second, has anyone put wood with active lyctid PPB in a vacuum system, used the vacuum and temperatures normally used and seen no activity over a year's time? Obviously, the wood in this case needs to be held a year in 70-90 F, as freezing delays the activity. Further, the life cycle of the insect, from freshly laid eggs to h emerging of the insect is roughly a year, so inspection for a year after drying would be needed.
Here is an issue I have. An oak floor has lyctid PPB. The wood was supposedly dried in an IDry.. in conventional drying cases, as we go over 150F, we can correctly assume that when the wood leaves the kiln, it is free of the living insect, eggs, larva, pupa. So, we look for an infection occurring after vacuum drying. So, with IDry or similar vacuum system, can a statement be made about freedom of vacuum wood fromPPBs? If yes, what proof is there? If the vacuum is turned off and the wood is heated to 133 F through and through while in the chamber, are there recordings of the temperature that could be used to "prove" this sterilization was used?
Looking at the specs on the iDry web page is says
"Heating: Electric (185F max temp)"
That suggests to me that it can do a sterilise cycle at the end of the drying process?
I don't have the answer for a vacuum alone system. The iDry only uses a partial vacuum (like going to ~30,000 ft) which probably isn't enough to kill bug eggs.
I also found this Patent for killing bugs in wood via vacuum desiccation, but it doesn't specifically mention PBB, so may not apply directly, but they had done some research on time / temp / vacuum that was needed to kill the various bugs.
US7739829B2 - Killing insect pests inside wood by vacuum dehydration - Google Patents (https://patents.google.com/patent/US7739829B2/en)
Gene, I don't have the references to back it up, but several years ago I was told (by Den Socling) that deep vacuum and RF vacuum kilns will kill all bugs, eggs and larvae, but shallow vacuum kilns such as the iDry require heat sterilization.
I was under the impression that the vacuum had to exceed -27" in order to kill all bugs.
I recall Jim Parker telling me that the iDry used heat to sterilize when I toured his manufacturing plant in 2019.
Unfortunately I don't have any technical docs to back that up.
Not real proof. But a real world trial i call it.
When I first got my idry, 4 years ago, I dried some oak and ash. It would have gone to at 150 -160 F at 8" of vacuum. I found this wood still stickered (only 4 rows)like it went from my old yard into the kiln on my shelves in my shop a year or so later with the tell tale small piles of sawdust on the board below, It was only under 4 boards. I could not tell how fresh the sawdust was. I quickly removed and burned that wood. I have since ensured I turn the kiln up to 165F for the sterilization part of a cycle of drying. This ensures the wood goes above the 150F .
I store all KD wood in my climate controlled shop. I have never seen any other signs of the PPB in the shop. I know I would have dried other contaminated wood from my old yard as it was all stored together. I still have a lot of the oak stored on shelves with no signs. I check all the time looking for sign.
I am a lot more concerned now as I have gathered more knowledge and take great care to ensure my yard is clean. If people want their wood sterilized because they have seen signs of insects, I only allow the wood on my property the day it goes in the kiln. I then ensure the kiln goes to 165F for at least 24hrs.
Bear in mind that vacuum is not an accepted way to kill insects in wood, according to government specifications. Fumigation and heat are the accepted methods.
I have looked into this, off and on, for quite some time and although PPB mortality is vague, there is some detailed research of using vacuum to kill other insects, most notably in bulk seed crops such as rice, wheat and corn to avoid long storage damage and get away from using pesticides. Also, there is a case for using non pesticide or heat sterilization techniques or more typical household items where pesticides are not a good alternative, such as eradication of bedbugs and their eggs.
https://academic.oup.com/jee/article/109/3/1310/2648749 (https://academic.oup.com/jee/article/109/3/1310/2648749)
Of interest to me is that in many cases the cause of death seems more of an oxygen deprivation scenario, vs a pressure or vacuum level dependent. The two are coupled however, as the lower the vacuum, the lower the oxygen levels. -29 inHg is the number I seem to find most often. 1% oxygen seems to be significant and 0.1% seems to be unsurvivable, and the research is loosely termed ULO (Ultra Low Oxygen) extermination. There is also some research going on that is using inert gas under pressure, such as nitrogen, to displace the oxygen and achieve a ULO environment.
The moisture content of the material the insects are in also have a significant input, with some research indicating desiccation was the main cause for mortality. ULO treatments will kill them at all moisture levels of host material, however increased moisture levels will increase the treatment times significantly. Seeds and some other substances can't be dried to as low a level as wood, so that's why ULO is important.
Personally, I have a hard time agreeing with the vacuum desiccation theory, because if true, then any DH or dehydration unit would kill all life cycle phase of the insects, including eggs. I can see desiccation killing fluid filled larvae, but not so much eggs.
As Gene mentions, according to my licensed professional exterminator, (we have discussed this many tines) the only two methods that he can sign off to an insurance company is heat and fumigation using an approved pesticide and technique.
Just throwing this out there. Do any of you know if radiation has been used to sterilize lumber? Several years ago, a controversial business south of here in Mulberry, started irradiating food. It was deemed safe, but the food was not readily accepted by many. If it is an effective treatment on lumber, I wonder if it would be cost effective.
Food Irradiation | US EPA (https://www.epa.gov/radtown/food-irradiation)