The shaded, dry space under a deck is one of the most common places for wasps to build in Boise. The joists and boards keep rain off the nest, and nobody spends much time under there, so a colony can grow all summer before anyone notices. Then someone steps off the stairs, mows near the edge or reaches under for a hose, and the wasps respond.
Here’s how to tell what’s nesting under your deck, how to check safely and what you can do to keep them from coming back.
Which Wasps Nest Under Boise Decks?
- Paper wasps. Long, slender bodies with dangling legs in flight. They build open, umbrella-shaped combs attached by a single stalk to joists and the underside of boards.
- Yellowjackets. Shorter, stockier and bright yellow and black. They build enclosed paper nests in hollow spaces under decks, in wall voids or in the ground beneath the deck. Yellowjacket colonies can get large by late summer and defend the nest aggressively.
- Bald-faced hornets. Black and white. They build large, football-shaped paper nests, usually higher up, but sometimes under elevated decks.
Our wasp identification guide has photos of each.
Why Decks Make Good Nesting Sites
Deck undersides offer protection from wind and rain, steady shade and a framework of joists to attach a nest to. Gaps between boards give wasps easy entry, and soil under low decks gives yellowjackets a place to dig. Food nearby, such as patio dining, open trash cans, fallen fruit and pet food, makes the spot even better for them.
How the Season Plays Out
In spring, a single queen that survived the winter starts a small nest and raises the first workers. Through summer the colony grows quickly. By August and September, a yellowjacket nest can hold hundreds or even thousands of workers, and they get more defensive and more interested in human food. After the first hard freezes, the workers die off and only new queens leave to overwinter. Old nests aren’t reused.
That means the easiest time to deal with a nest is early in the season, while it’s small.
Signs of a Nest Under Your Deck
- Wasps flying in and out of the same gap between boards or near the base of the stairs
- A steady flight path to one spot in the ground beneath a low deck
- Gray paper combs attached to joists when you look underneath
- Chewed, grayish streaks on untreated wood, where wasps scrape fibers to make paper
How to Check Safely
- Watch from a distance first. Look for where wasps come and go rather than crawling under the deck.
- Check in the cool of early morning or late evening, when wasps are less active.
- Wear long sleeves and long pants, and avoid strong scents.
- Don’t block a nest entrance or poke at a nest. Yellowjackets will defend it.
Anyone with a known allergy to stings should stay away from the area and let someone else handle it. Signs of a serious reaction, such as swelling of the face or throat, trouble breathing or dizziness, need medical attention right away.
Should You Remove It Yourself?
A small paper wasp comb, a few cells and a few wasps, can sometimes be knocked down early in the season. Larger nests, enclosed yellowjacket nests and anything in the ground or inside a void under the decking are a different story. Spraying into a gap often just makes wasps come out angry, and the nest itself may be somewhere you can’t reach without pulling boards. Our post on what to expect from wasp nest removal walks through how a professional handles it.
Keep Wasps From Coming Back
- Inspect early. Check under the deck in April and May for small starter nests.
- Close gaps. Seal openings into hollow areas and around the deck skirting where yellowjackets can get in.
- Remove old nests in winter, once they’re empty.
- Manage food. Keep lids on trash and recycling, clean up after outdoor meals, pick up fallen fruit and bring pet food in.
- Maintain the wood. Painted or sealed wood is less attractive to wasps scraping fibers for nests.
- Check the rest of the house too, including eaves, play sets and sheds. Our wasp nest removal tips cover other common spots.
Professional Wasp Control
Wasps and hornets are part of our residential pest control, along with spiders, ants, mice, rats and fall invaders. We offer quarterly, bi-annual and one-time service. Quarterly service plan customers get free return visits. No contracts; cancel with 30 days’ notice. We also handle wasps around decks, patios and entrances at commercial properties in Boise.
The University of Minnesota Extension has a helpful overview of wasps and bees, including how to tell yellowjackets from beneficial bees.
Wasps Under Your Deck?
ProGuard is based in Eagle and serves homes and businesses in Boise, Meridian, Nampa, Caldwell, Star, Middleton, Emmett and Garden City. Call (208) 352-2062 or contact us to schedule wasp nest removal.