I've used borax and boric acid many times as a pesticide mostly against mold and rot on wood and other building materials like drywall. It works well for insects like termites and ants too, and it even makes the wood fire retardant. But it leaches out if the stuff gets too wet, so it won't last long out in the rain....so it's not much good for outdoor uses like fence posts. For bamboo, I learned years ago at a workshop that you want to cut stalks at least three years old....these are fully mature. With many species you can distinguish the older canes because the ring of wax just under each node will turn from white to black. After harvest, it's then recommended to leach the bamboo for a month or more under water, preferably running water. For whole canes this can be done by tying them together in bundles and then making a raft of them, and then pile heavy things on the raft so that it is held just under the surface. If you want split bamboo, it's easier to split it green, and then bundle the splits and leach them....split bamboo will often sink of itself; or will need a lot less weight to hold it under. Then after the leaching, pull it out and let it dry slowly in the shade. The water supposedly leaches out the starch and sugars in the fibers, which are the main attractant to insects. Drying slowly helps the bamboo cure with minimal cracking....which is desirable for whole canes for building purposes. There are all kinds of exotic treatments to be read about out there....some involve cutting the bamboo, and leaving it in the grove, held up by the surrounding bamboo, and then right away standing the cut ends in a bucket of preservative, so that the transpiration of the green top will suck the solution up through the fibers....this however would leave the bamboo unleached and full of sugars etc. An even more intensive design I saw involved welding several metal barrels together end to end, without the ends on the center ones, so as to create a long metal tube that could be sealed with a removable lid. Bamboo canes are loaded into this, bottom ends all toward one end, and a small amount of water added. The whole thing is then stood up and a fire kept going under the bottom end. Supposedly the water boils and forces it's way up through the channels in the bamboo and then condenses back down, which dissolves the sugars, melts the waxes, and alters everything such that the stuff is preserved in it's own juices. After a few hours of this it's left to cool and taken out. Recalling it makes me interested to read about it again and see if it's myth or fact...has anyone else ever heard of this?