when do the queens generally emerge to start their new nests?

I'm in central PA.

As soon as conditions are right. We are in that transition process currently in SW Pa.

appreciate the reply, Bob!

thinking I should put out a couple wasp/hornet traps soon.

It takes several months for them to build and develop a brood and nest site.

I appreciate your help/knowledge, Bob!

Thank you!

I saw the first paper wasps of the season on Monday. Eastern, PA. It'll be weeks before nests start developing.

Nothing here yet. But we started this week with a good amount of snow on the ground. It’s finally back enough that we have been able to start spraying. We saw our first pavement ants yesterday.

They've emerged here but I won't get calls for them until mid June or later, usually later. I do see the foundresses out foraging well into May.
As Bob said they take time to build up as the foundresses have to start from scratch doing everything from initial site selection, building initial paper nest, egg laying and provisioning the brood. It's only when that brood emerges that growth becomes exponential.

I was hoping to thin out the queens in my local area, to reduce the chances of a nest where I mow.

It is very difficult if not impossible to compete with nature. At least on the scale that you have in mind. Particularly those that are mobile with flight capabilities. If the conditions are there, they will set up house keeping. They are great for the environment on the flip side.

It’s all about habitat.

Ever notice how few lightning bugs there are in a suburban area vs the country? I remember catching them all over when I was little. Too many people are overdosing their yards with pesticides.

yes, you're right, Bob.

I just feel better reducing (at least a little!) the chances of them nesting here.

kinda like reducing carpenter bees...yeah, they're still around, but the thirty or so I caught aren't.

Paint or replace the wood the carpenter bees are in to keep their pheromones from drawing new ones in.

thanks, EBL!