First, I suggest you read through our POWDERPOST BEETLE CONTROL article. There you will learn the best products to use when treating this pest. As explained in the article, TIMBOR is really only good for preventative treatments and won't help much for anything established and currently active. The BORACARE is clearly the product needed here if you wish to get the much needed penetration for complete control. Remember, what you see at the surface of the wood is only the tip of the iceberg; most of the action will be deep down at the center of support beams and other large important structural members of the house and therefore be out of sight.

Second, there is no "fumigation" option other than tenting the house that would help. Total release aerosols aren't going to penetrate the wood where the larvae are feeding so forget this approach.

Third, as our article explains, it's generally best to treat as much of the lumber as you can. Since you have a crawl space and what sounds like an accessible attic, you should be able to see any activity and focus your attention on these areas. And be sure to treat surrounding wood. Wall voids are difficult to spray and if you feel they could be active in such spaces, get the FOAMING TOOL and inject the Boracare as we explain in our article.

Lastly, the only aerosol that can help at treating the problem would be something like the BAYGON or PT-CYKICK and in order for either work, they must be injected directly to beetle galleries and access points. To accomplish this, you'll need to drill holes large enough for the injecting straw of the aerosols to fit where you want to treat. Drill patterns should be spaced 6-8 inches apart and the goal is to create a direct way for the aerosol to reach deep into the wood where the larva are feeding. Failure to "hit" galleries with the drill holes means the treatment will usually fail which is why Boracare is almost always your best bet when you need maximum coverage. The penetrating quality of Boracare makes it worth the extra cost since you know it will get deep down where it matters most when dealing with this pest. The advantage of the Boracare is that you won't have to worry about drilling anything; it will penetrate and get to where it's most  needed.

Here are direct links to the products and information listed above:

http://www.powderpostbeetles.com/powderpost-beetle-control

http://www.bugspray.com/catalog/products/page51.html

http://www.bugspray.com/catalog/products/page52.html

http://www.bugspray.com/catalog/products/page1069.html

http://www.bugspray.com/catalog/products/page157.html

http://www.bugspray.com/item/pt_cykick.html

Powderpost beetles can do a lot of damage if given the chance. In most cases, they're not detected till something significant has been discovered so whats happened is fairly common. Also, it's not uncommon for their activity to be limited to one piece of wood. In other words, they could be in just that one piece (and hopefully so). That being said, the first order would be to treat the wood with activity, along with all the other accessible areas, to insure the problem is not more wide spread and that if it is, the damage won't get worse.

Once the area has been treated with something like the Boracare we have listed in our powderpost beetle control article, it would be wise to get a knowledgeable expert to inspect the floor joist to see what needs to be done. In most cases, "sistering" or attaching another joist to the damaged one will do the job. Leaving the old one in place would be fine and probably best; the new one would then take on the weight of the structure and the old one would be left to support what it can.