Other Other Than A Spray, What Other Ways Are There To Kill Wasps And Their Nests In Hard To Reach Areas?

Other than a spray, what other ways are there to kill wasps and their nests in hard to reach areas? - other

I have wooden staircase leads to a lake behind my house. Apparently the wasps built a nest under the measure itself and have no access to reach the crest between the tables. This has been unsuccessful. How can I kill the wasps and to tear the nest, without the boards?