There is so much bad advice on this thread; I just had to chime in.
First of all, DO NOT TRY AND BOLT IT TOGETHER.
Second of all, Weld-Wood will never work. It is an epoxy and will stick to your truss rod, making it inoperable. Don't do it.
You absolutely do NOT want to use epoxy, particularly not thickened epoxy. The goal is to bring the pieces of wood back into alignment, and you will never do that with any kind of epoxy, plus (as I have already stated) epoxy will get into the truss rod slot, and will make your truss rod all but inoperable. Epoxy has basically no place in guitar repair, EVER.
The correct repair for that one is to replace the neck. If you can't do that, take it to a good repair shop. At my shop, what we would do is work some Tightbond into the cracks (probably just with our fingers, but in some instances we use a syringe with a fat needle on the end). To clamp it, we would wrap sections of bicycle innertube around the neck repeatedly, probably 8-10 wraps around the area. Pull it as tight as possible with each wrap, and it gets tighter and tighter, and pulls every thing together. This probably would not work with this crack, but it might. If it does, make sure you do not get your guitar hot, as the glue will at the very least creep, and may just let go all together.
But the right repair is absolutely, without question, to replace the neck.
Light
"Cowards can never be moral."
M.K. Gandhi