Hey there fellow beekeepers:
Someone said nothing better than untreated burlap, but there is; and it's free for the picking.
If you or a friend or neighbor has cattle, just pick you up a sack of dry cow patties. This makes a smoke superior to all in my opinion. Matter of fact, sometimes here in La. we make a "smoke" in a small iron pot on the porch, we have no misquito or gnat problems, then.
Try it; you'll like it, and best of all it's free. I'm lucky to have a huge supply, but again, a little goes a long way.
All the best,
casper_zip