When I first started harvesting green wood for my workshop, I was worried about bringing wood-boring insects into my workshop. It would be like letting loose 1,000 racoons into a Golden Corral restaurant.
So I got some advice from fellow woodworkers. All of the advice involved pesticides. And some of it sounded reckless. (Put the wood in a garbage bag with an aerosol bug bomb. Be sure to tie up the bag really quick!)
Years ago, I found this short article by Michael F. Potter, an extension entomologist at the University of Kentucky College of Agriculture, and it was exactly what I wanted. Potter recommends eliminating insects from the wood using your fridge or your oven.
I’ve been using his freezing method for several years, and it has worked brilliantly.
In short: Put the wood in your freezer and set it for -4° F. Let the wood stay there for seven days. Remove it. Done.
Potter recommends using a plastic bag to protect the wood, but he’s mostly concerned about finished household items. I haven’t found it necessary when freezing raw wood.
The article also discusses how to kill bugs with your oven and gentle heat. I haven’t tried this method yet. I want to experiment first with some test pieces that are green because the method might rapidly dry out the stock and check the ends. (Potter does recommend adding a pan of water to the oven to keep the humidity high. I am interested in this technique; I just haven’t had time to give it a go.)
Another bonus with the freezing method: If you keep the green wood in the freezer it won’t dry out and will stay green as long as it’s frozen.
All this is just another excuse to add a beer fridge insect deinfestation device to your workshop.
— Christopher Schwarz
Another good reason to use a freezer instead of an oven is that, if you’re working with larger pieces, it’s much harder to find a chest oven than a chest freezer
In the museum, where I volunteer, we freeze everything of wood, textile or paper that is new to the collection for 14 days at -20°. Well, as long as it fits the freezers.
Steaming is very effective but it does dry the wood out, as in kiln dried.
I’ve lived very far north most of my life. I have experienced 60 below zero, and most winters 40 below is not unusual.And our winters are long. Yet bugs live through it just fine. So freezing at -4 ? Why aren’t all the bugs who eat wood, dead here?
I bring air dried and some green wood into the house, and I’ve never experienced any wood boring insect mayhem. I have found live and dead insects and larvae in wood. Maybe I’ve just been lucky, or maybe Wisconsin’s wood borers aren’t as aggressive as Kentucky’s.
Maine Shakers in the late 19th and early 20th century worked wood while it was green and frozen. They made wee poplar strips that they wove into cloth in the middle of the winter, fresh off the log. And made 1/16″ maple bands for oval boxes, in December, before it dried. Lacking drum sanders they could plane the wood really thin, because it was green and frozen. It’s on my list of things to attempt.
Was in Alaska recently and talked to a local artist doing a residence at a native museum in Juno. They do the same with yellow cedar there in their weaving. Got to see and touch some of the fabric with and without. Makes a big difference in fabric.
Thanks Chris. The local wood turning club has done an excellent job of interfacing with folks who cut down local trees so that the wood can get used and i received some. It put it on my shelf to dry and a few months later I saw some dust piles indicating bugs in wood and freaked out. ACK! Tossed the wood and swore never again (till I read this). Been a year plus since this incident and no new bug dust piles so luckily looks like bugs stayed in the nice wet wood rather than transferred into my kiln dried wood. Phew.
I was gifted the logs from a freshly cut locust tree. When I opened them up, the last log was chock full of large, plump borers, probably why the tree had to come down. I placed it at the border of my back yard and the woods behind us, and watched the show. Every woodpecker in the area invited their extended family to feast on the log. A big pileated woodpecker then showed up, and made short work of it. Not all wood is destined for heat or the crafts.
The freezer is standard in museum land, essentially for everything timber or fibre based (and other things). We tend not to put things in the oven.
Many borers are only capable of utilising wood at at fairly narrow range of moisture contents, so if you cut down a tree and find bugs in it they will mostly die out as the wood dries and won’t be interested in your already dry stock. That’s nice reassurance but doesn’t help you keep the green piece they’re already munching on.
Other appliances you can use are a heat gun and a box to heat the wood core to 56°C (°134F) for a half hour , or for small ítems, heat the core in a microwave to 60°C (140°F) for 1 minute. Don’t come crying to me if you burn your house
https://research.fs.usda.gov/download/treesearch/12473.pdf
One caveat. Wood borers will re-infest the bark in live edges, given the chance.
Hi Chris. I live in a freezer (Alaska). I have been storing my wood in an unheated shed for years. I didn’t even know I was eliminating wood boring insects! I suppose I never had to think about that particular problem.
Facts Only
Christopher Schwarz harvests green wood for his workshop.
Michael F. Potter is an extension entomologist at the University of Kentucky College of Agriculture.
Potter recommends using a freezer set to -4° F for seven days to eliminate insects.
Potter recommends using an oven with a pan of water to maintain humidity for heat-based insect elimination.
Museum professionals freeze new wood, textile, or paper collections for 14 days at -20°.
Maine Shakers in the late 19th and early 20th century worked with green, frozen poplar and maple.
Alternative heat methods include using a heat gun to reach a core temperature of 56°C (134°F) for 30 minutes or a microwave to reach 60°C (140°F) for one minute.
Wood borers typically operate within narrow moisture content ranges.
Wood borers can re-infest bark on live edges.
A USDA Forest Service research document is cited.
Executive Summary
Eliminating wood-boring insects from green wood is a primary concern for woodworkers and museum curators. While chemical pesticides are often suggested, non-toxic alternatives center on extreme temperature shifts. Freezing is a widely adopted method; professional museum standards suggest 14 days at -20°, while a common workshop recommendation is seven days at -4° F. This method also preserves the "green" state of the wood by preventing drying.
Thermal alternatives include using an oven, heat gun, or microwave to reach specific core temperatures. However, heat carries the risk of rapidly drying out the stock or causing checks in the wood, which can be mitigated by adding water to an oven to maintain humidity. There is some anecdotal uncertainty regarding the necessity of these measures, as some individuals in extremely cold climates report no insect infestations despite storing wood in unheated sheds. Ultimately, the efficacy of these methods may depend on the specific species of borer and the moisture content of the wood.
Full Take
This discourse is a blend of anecdotal experience and professional guidance, moving from the personal workshop to the museum archive. The strongest version of this narrative is that temperature control—specifically deep freezing—is a safe, effective, and reversible way to manage bio-hazards in organic materials without resorting to hazardous chemicals.
The text operates primarily through "social proof," aggregating testimonials from woodworkers, museum volunteers, and historical accounts of the Maine Shakers. It presents a decentralized knowledge base where professional entomology provides the baseline, but practitioners refine the application through trial and error. A notable tension exists between the "laboratory" requirement (specific temperatures and durations) and the "environmental" reality, where individuals in Alaska or Wisconsin observe that nature's own winter doesn't always kill all borers, yet their workshops remain clear. This suggests an unstated assumption: the difference between a dormant insect in a forest and an active infestation in a concentrated workshop environment.
The root paradigm is one of stewardship—preserving the integrity of the material while protecting the sanctuary of the workspace. The implication is that human agency is enhanced when we move away from "reckless" chemical interventions toward an understanding of the biological limits of pests.
Patterns detected: none
If this were a coordinated influence campaign, it would likely use "fear appeals" regarding the destruction of valuable collections to sell a specific brand of industrial freezer. The actual content is a peer-to-peer exchange of hobbyist and professional techniques, lacking any commercial driver.
Bridge Questions:
1. Why does the "natural" freeze of a northern winter fail to eliminate borers while a controlled freezer succeeds?
2. How does the moisture content of "green" wood specifically shield insects from extreme cold compared to seasoned wood?
3. To what extent does the "museum standard" of -20° for 14 days differ in efficacy from the "workshop standard" of -4° for 7 days?
Sentinel — Human
The text reads as a personal reflection synthesizing practical, experiential knowledge about wood preservation and insect control, framed through personal experimentation rather than objective reporting.