What 30 Years Has Taught Us About Wasp Nests in Pennsylvania

Know your enemy. Respect the hole in the ground. And please make sure it isn't a honey bee before reaching for the spray.

After treating more than 1,000 wasp and hornet nests across the Lehigh Valley, we've learned one thing very clearly: late summer is when these colonies mean business.

By August, many social wasp colonies are reaching their largest populations of the season. Nests that started with a single queen in spring have spent months producing workers, expanding the nest, and gathering food. Now colony growth is in full force as reproductive queens and males begin to be produced for the next generation.

Unfortunately, this is also when homeowners tend to discover them—often by accident.

That Hole in the Ground Deserves Respect

One of the most common calls we receive this time of year starts with something like:

“I was mowing the lawn and suddenly got stung six times.”

Ground-nesting yellowjackets can establish colonies in abandoned rodent burrows, voids beneath landscaping, retaining walls, tree roots, and other protected spaces. The entrance may be no larger than a quarter.

What you can't see is what's underneath it.

A mature yellowjacket colony can contain hundreds or even thousands of individuals, depending on the species and conditions. Stepping near the entrance, running a mower over it, or sticking a garden hose into the opening can trigger a defensive response from a lot more wasps than the handful you saw flying around.

Our rule after more than 1,000 nests?

If insects are repeatedly flying in and out of a hole in the ground, give it space.

Know Your Enemy

Pennsylvania has a surprising number of little striped things capable of stinging you, and they're not all the same.

Yellowjackets commonly nest underground or inside structural voids and can aggressively defend the colony.

Bald-faced hornets construct the large gray paper nests commonly seen hanging from trees, shrubs, and structures.

Paper wasps typically build smaller exposed comb nests beneath soffits, railings, decks, and other protected areas.

European hornets are much larger and often establish colonies inside hollow trees or structural voids.

And then there are honey bees, which aren't wasps at all.

Correct identification matters because the appropriate response can be completely

different depending on what you're dealing with.

Please Don't Spray Honey Bees

Seeing a cloud of insects does not automatically mean you have a wasp nest.

Honey bees may temporarily gather in large clusters while swarming, establish colonies inside structures, or forage heavily around flowering plants.

County Pest maintains its own apiary and performs honey bee removals and relocations when practical. A honey bee colony should not be treated like a yellowjacket nest simply because both insects can sting.

Identify first. Treat second.

That's Integrated Pest Management in its simplest form.

Wear Protection—or Call Someone Who Does

One lesson becomes increasingly obvious after treating this many nests:

Protective equipment exists for a reason.

Approaching a mature yellowjacket or hornet colony in shorts and flip-flops with a can of hardware-store spray is a remarkably unfair fight—and you're not the one with the numerical advantage.

Professional treatment isn't simply about having a stronger product. It involves identifying the species, understanding where the colony is located, evaluating possible secondary entrances, choosing the appropriate treatment method, and wearing the protective equipment necessary to safely work around a defensive colony.

The Nest You See May Not Be the Nest

This is especially important with structural nests.

Watching wasps disappear beneath siding or through a small opening doesn't mean the nest is sitting directly behind that hole. Colonies may occupy wall voids, soffits, rooflines, hollow block, insulation cavities, or other protected spaces.

Simply sealing the entrance can sometimes make the problem worse by forcing insects to search for another exit—which may be inside the house.

That's why inspection matters.

Late Summer Is Peak “I Didn't Know That Was There” Season

Throughout spring and early summer, colonies can remain surprisingly easy to overlook.

Then populations increase.

More workers are traveling to and from the nest. More food is required. Nests expand.

Activity becomes easier to see.

And suddenly the shrub you've walked past for three months contains a bald-faced hornet nest the size of a basketball.

Or the harmless-looking hole beside the shed turns out to have several hundred very unhappy occupants.

What 1,000+ Nests Have Taught Us

After enough wasp calls, the advice becomes pretty simple:

Know what you're dealing with.

Respect ground nests.

Understand that the ten wasps you see may represent hundreds more you don't.

Don't seal an active structural nest without understanding where it leads.

Wear appropriate protection.

Never assume honey bees are wasps.

And when the nest is large, hidden inside a structure, underground, difficult to access, or simply outside your comfort level—call a professional.

There are plenty of DIY projects worth tackling around the house.

Picking a fight with several hundred yellowjackets doesn't need to be one of them.

If you need help you can find more information here.

County Pest Control — Where Service Meets Science.