Sunday, March 12, 2006

Powder Post Beetles

Perhaps you've been in an old barn or log cabin and have seen tiny holes in the timbers. More than likely, these are the handywork of a category of beetles known as powder post beetles. Ones that I've observed crawling (an "gnawling") on my timbers include the death watch beetle, the ambrosia beetle, and the true powder post beetle. From what I have read, the damage to my timbers in the picture above was likely inflicted by the larva of the adult beetles that hatched within the wood.

In an attempt to protect my frame from these pests for generations to come (or at least protect it until I can get it finished!), I bought into the idea of using a borate solution marketed as "Boracare." Applied as directed by the manufacturer, it did not prevent these beetles from infesting and damaging the wood my wood. Shocked by the degree of infestation that has already occurred to my treated timbers while sitting in the barns, I rechecked the label on the Boracare bottles (I have quite a collection - at $90 a bottle, I couldn't bring myself to throw away the plastic containers even though they were empty!). Sure enough, they have a disclaimer that basically says they won't guarantee their product to prevent infestation of your timbers. Hmmmm. Non toxic to humans and lasts forever... if it sounds too good to be true, maybe it is. Perhaps the Boracare will prevent reinfestation of my timber frame by these little pests. One can hope.

One particularly voracious beetle, the ambrosia beetle, especially likes yellow poplar, maple, walnut, and chestnut oak. This beetle works on green wood, prefers sapwood, and the ADULTS do the damage. I have left boards next to my sawmill overnight, only to return the next day and find that it looks as if they've been peppered with a shot gun. These beetles work FAST. Within 12 hours, they can bore about 1/8th inch into the wood. If you pour diesel on them, they back out of their holes and die within a minute. (I don't recommend diesel... its just what I had handy at the saw mill!) If you pour undiluted Boracare on them, they plow around, pull theirselves out of the puddle, and start boring again! I took a mason jar full of these live critters to a KY state forestry worker, and he took them to an entomoglogist at UK and they ID'ed them for me. It looks like they have two segments to their bodies, because their head is tucked under their midsection. They are usually black (sometime with a reddish segment) and about the size of a poppy seed. At certain times of the year, the air is thick with them flying and you might mistake them for gnats. They bore and lay their eggs in the sappy wood, where conditions are just right to grow "ambrosia" (beetle beer). When the youngsters hatch, they drink the fungal fermentation. This is what I've been told, and observations support this. Consequently, I've been told they do not work on dry wood, and would likely not re-infest my wood once it is inside my house and dry. I hope this is true, because they can take a beautiful (green) board or timber and perforate it in less than 24 hours. Years later, you can tell a board that has been damaged by this particular type of beetle (as opposed to other powder post beetles), because the hole they left will have black around it... from the fungal growth that happened because the wood was damaged while it had sap in it. The saw dust that comes out of their holes usually looks like little soda straws. I have even seen them working on _live_ yellow poplar trees. Believe it or not, I even found one in an ear of corn. (Sorry I have no personal pictures of these buggers on my farm right now - the picture above looks just like it though - right down to the reddish midsegment that looks like its head. Ambrosia Beetle ©2002. The Bug Network, Image Courtesy of: Steve Passoa - USDA APHIS PPQ)

Kiln drying at high enough temperatures for long enough periods of time is said to kill the adults as well as their eggs (this goes for all of the types of wood boring beetles), and while this was possible to do with our tongue-and-groove ceiling boards, it was not feasible for our timbers. Because I oversized the timbers in our house, I'll just keep telling myself that there's enough timber to share with the bugs. None of our old barns have fallen down yet from their munching.


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