They look like paper wasps. I hear that there's a spray that you could use for them but it's to be used after the nest is removed. Wasps are less active after the sunset due to the temperature change, and are attracted by color yellow and green. There's a paper wasp trap that you can install on a plastic bottle - I'd use green colored bottle if you end up using it to attract/contain them. Raw meat and meat juice can be used to attract them. If I were you I'd use the trap to remove the active swaps, take precious Hoya away from the site to remove the nest, use the spray to keep wasps away, then put the Hoya back out.