Does anyone have an answer to stopping wasps mostly from flying under or crawling between the deck boards of a raised deck and making nests in between the floor joists?
Every year this is a constant battle and a complete pain to deal with.
I have hung differnt things to lure in Bees but they are attracted to sweet things which the wasp is not.
I dont know of any spays that could be sprayed underneath to deter them before they make a nest.
We had a warm day yesterday here in South Jersey and i actually saw a wasp already.
Let the battle begin!
Tell me your secret!

Probably the best way to get a handle on them is to get them early. This means killing the wasp that is starting the nest when it is just her and no other workers present. In doing so, this may mean that you crawl under there and hit them with wasp freeze one at a time. If the colony is established later in the season and you can't score a direct hit on the nest with wasp freeze, you can get a dust that penetrates voids sort of like smoke. It will eventually make it to the nest and kill the wasps. Google Drione dust if you are interested in the dust. You'll need a duster from the company.

If the insects under your deck are honeybees and not wasps, call a professional. You can't eliminate a colony of honeybees on your own. Anyway, by dealing with the wasps early and by knocking down their nests, it makes the area less attractive to future wasps.

Spray the underside of the deck with WD-40. It'll keep them from building for a while. You'll probably need to respray every couple of months.