The short version
Wasp control in Colorado now revolves around the European paper wasp, an introduced species first recorded in Larimer County in August 2001 that Colorado State university extension calls very abundant in every urbanized county in eastern Colorado, plus Mesa, Montrose and Delta counties. It nests in grills, pipes, rock cavities and wall voids from Denver to Grand Junction and is treated with aerosol or dust at the nest, while western yellowjacket ground nests get dust at the entrance. Everything dies at the 18F winter.
- Wasps are most active from July to October in Colorado, with peak aggression in late summer.
- Professional removal costs $100–$600 depending on nest size and location.
- DIY methods are risky; stings can cause severe allergic reactions.
- Prevention includes sealing entry points and removing food sources.
- Ask about an inspection or a quote.
Front Range homeowners who opened the grill or the mailbox and found a comb inside, people in Aurora, Lakewood or Westminster with wasps going into a gap in the siding, anyone in Grand Junction with the same European paper wasp problem on the Western Slope, and property managers across Denver and Colorado Springs facing spring complaints. If the insects are fuzzy and there is wax comb, that is a bee colony and a beekeeper's job.
What to look for
Native paper wasps, the brown Polistes, still build open combs under eaves in Pueblo and the plains towns, but the newcomer has pushed them aside along the urban corridor. The western yellowjacket is the ground nester and the picnic pest. It uses old rodent burrows and gaps under decks and patios, builds a colony through the summer, scavenges hard in September, and, per Utah State university extension, dies off each fall with only fertilized queens surviving. Bald-faced hornets hang gray ball nests in cottonwoods and on eaves in Boulder, Longmont and Loveland. The climate keeps it honest. An 18F median winter low across our 19 cities kills every colony; nothing carries over. The European paper wasp is Colorado's main wasp now. It is yellow and black and slimmer than a yellowjacket, and it gets misidentified constantly. Colorado State university extension notes its earliest activity is sometimes seen in the first half of March, that each colony is established anew each spring, and that a nest may hold several dozen individuals by the end of summer. Small colonies, but everywhere. CSU lists its nest sites as outdoor grills, large bells, pipes, rock cavities and hollow spaces behind walls, which describes the average Colorado backyard: a grill on the deck, rock landscaping instead of lawn in a 16-inch-rain climate, and a house with vinyl or fiber-cement siding over a wall void.
- 1Visible nests under eaves, in attics, or in ground holes.
- 2Frequent wasp sightings near trash cans, picnic areas, or gardens.
- 3Chewed wood or paper-like material on structures.
- 4Audible buzzing from walls or ceilings.
- 5Aggressive behavior when approaching certain areas.
- 6Dead wasps near windows or doors.
- 7Multiple wasps entering a single hole in the ground or wall.
Why it’s worth acting soon
- Nest size and wasp numbers increase rapidly, especially in late summer.
- Increased aggression as food sources dwindle in fall.
- Structural damage from nests built in walls or attics.
- Health risks from stings, including anaphylaxis.
- Negative impact on outdoor activities and business reputation.
Treatment options and typical costs
Aerosol or dust into a cavity nest
Quoted after inspection
European paper wasp combs in grills, pipes, bells, fence caps and rock crevices are treated with a long-range aerosol at dusk or with dust puffed into the opening. The comb is removed once the wasps are dead. A pro will check every likely cavity on the lot, since CSU notes this species uses many odd spots.
- Time
- Same visit
- Best for
- European paper wasp nests in grills, pipes, rock landscaping and fixtures
Dust into a wall void behind siding
Quoted after inspection
When wasps are entering a siding seam or the hollow behind a wall, dust is applied at the entrance and the gap is left open for a few days before it is sealed. The pro should return to confirm activity has stopped. This applies to European paper wasps in wall spaces and to the occasional yellowjacket colony in a wall.
- Time
- One visit plus a check
- Best for
- Nests in hollow spaces behind walls
Dusting a western yellowjacket ground nest
Quoted after inspection
The burrow entrance is dusted at dusk, when Colorado's cool evenings bring the workers home early, and checked a few days later before the hole is filled. Nests under decks and patio slabs get the same treatment through the gap the wasps use.
- Time
- One visit plus a check
- Best for
- Yellowjacket nests in lawns, rock beds and under decks
Heptyl-butyrate trapping for western yellowjackets
Quoted after inspection
Western yellowjackets respond to heptyl butyrate lures. Traps hung in spring catch queens, and traps in late summer thin the scavengers around a patio, brewery beer garden or park. They do nothing for European paper wasps, which is the species most Coloradans actually have.
- Time
- Spring through frost
- Best for
- Properties with September yellowjacket pressure and no findable nest
Prices are typical published ranges. Ask what’s included before you compare quotes.
Yellowjackets often nest in old rodent holes and gaps in garden walls. Watch for wasps flying low and steady into one spot.How the European paper wasp took over Colorado.
There are just a great many of them, in every hollow thing you own. Each colony is founded anew each spring and holds several dozen wasps by the end of summer, so no single nest is large. CSU reports activity sometimes seen in the first half of March, weeks before native species stir at altitude. It also starts early. The grill on the deck, the hollow fence post caps, the pipe end on the irrigation manifold, the rock landscaping that replaces lawn in a 16-inch-rain climate, and the void behind vinyl or fiber-cement siding all qualify. A Colorado backyard is full of those. The European paper wasp uses cavities: CSU lists outdoor grills, large bells, pipes, rock cavities and hollow spaces behind walls. Native Polistes hang combs in the open under eaves. It won because of where it nests. CSU now calls it very abundant in every urbanized county in eastern Colorado, and it has largely replaced the native brown paper wasps around houses. From Fort Collins and Loveland it spread down the Front Range through Boulder, Denver, Aurora and Colorado Springs to Pueblo, and over the mountains to Mesa, Montrose and Delta counties on the Western Slope. Colorado State university extension dates the European paper wasp's arrival to a single record from Larimer County in August 2001.
wasps activity by season.
Scheduling before the busy stretch, rather than after it, tends to mean faster service and a more accurate quote, and a local provider can point out the conditions that matter most in Colorado. In Colorado, checking the foundation, gaps around doors and windows, and any moisture or clutter near the structure usually turns up the conditions that are letting them in. The most useful first step in Colorado is to note where you have seen wasps and when they appear, because that timeline is what lets a provider focus on the right area instead of treating the whole property.
Yellowjackets sometimes nest in attics and wall voids, getting in through a torn vent screen or a gap in the soffit. Buzzing in a ceiling is worth a look.The Colorado wasp year from March to the first hard freeze.
Colorado has no multi-year nests, which is why a late-October nest away from the house can usually be left. Only mated queens survive. The median winter low across our cities is 18F, and long before it reaches that, a hard freeze in October kills every worker and old queen. Then frost. Hornet nests reach football size. Paper wasp combs in grills and fence caps hold several dozen wasps, yellowjacket ground nests are at full size and turning to scavenging, and the calls come in from patios in Denver, Boulder beer gardens and Fort Collins backyards. August and September are peak. Everything grows quietly through June and July in the 88F summer heat and 50 percent humidity, with workers taking over foraging. April and May bring the western yellowjacket queens out to claim rodent burrows in lawns and rock beds from Greeley to Pueblo, and bald-faced hornet queens to start gray nests in cottonwoods and on eaves. Open the grill and the mailbox that month and you will catch combs at a single queen and a few cells. On a warm afternoon in the first half of the month, per CSU, European paper wasp queens that spent the winter in a wall gap or under bark come out and start looking for a cavity. March is when it begins on the Front Range.
What a wasp control visit looks like at a Colorado house.
And ask what they do if the insects turn out to be honey bees. Ask whether the return check and the sealing are included, and whether they cap posts and pipes as part of the job. Before the visit, ask how many nests the price covers, since a Colorado yard rarely has just one. A hornet nest within ladder reach is treated at its opening and bagged. A western yellowjacket burrow gets dust at the entrance at dusk, when cool Colorado evenings bring workers home early, and a follow-up before the hole is filled. A comb behind siding gets dust at the seam and a few days before sealing, with a return check. European paper wasp combs in reachable cavities get a long-range aerosol at dusk or a puff of dust, and the comb comes out once the wasps are dead. Then the yard for yellowjacket burrows, and the trees and gutters for a hornet nest. On a house in Centennial or Broomfield that means the grill, the fence post caps, the pipe ends, the hose reel, the mailbox, the hollow patio umbrella pole, every gap in the rock landscaping, and the siding seams and fixture backs where a European paper wasp might have found a wall void. A pro on a Front Range job spends the first few minutes on cavities.
Grills, fence caps and rock beds: prevention for Colorado yards.
And from late August on, keep trash, compost and fallen fruit covered, since that is when the scavenging starts. Hang a heptyl-butyrate trap at the lot line the same month. Fill old vole and ground squirrel burrows along the foundation and under the deck in April, before a western yellowjacket queen claims one. For yellowjackets, the yard matters more than the house. Reset loose rock tight. Seal siding seams and the gaps behind lights and hose bibs so combs stay out of wall voids. Plug fixture and bell cavities with mesh. Cap the posts and pipe ends. Then close what you can. Anything with a comb at that point is one queen and a few cells, and a broom handles it. In Denver, Lakewood and Grand Junction yards with rock landscaping, look into retaining-wall gaps and boulder crevices. Check the ends of pipes on the irrigation manifold and any decorative bell or lantern. Lift the mailbox lid and the caps on hollow fence and deck posts. Pull the cover off the hose reel. Open the grill hood and look under the grease tray and behind the tank. Start in the first half of March, when activity begins on the Front Range. The European paper wasp's list of nest sites, per CSU, doubles as a spring checklist.
When a Colorado wasp nest is urgent and when it can wait.
In every wait case, mark the spot, keep kids and dogs clear, and confirm nothing is flying on a sunny afternoon after the first hard freeze before you remove it. A bald-faced hornet nest high in a cottonwood away from the house in October, since the 18F winter is coming and the colony is weeks from dead. What can wait: a European paper wasp comb of a few dozen wasps in a fence cap on the far side of the yard, which you can handle at dusk this weekend. Treat it today when anyone in the home has a known venom allergy; the American College of Allergy, Asthma and Immunology puts potentially life-threatening reactions at about 3 percent of adults. The CDC's count of 788 sting deaths nationally from 2011 to 2021 is why nests by entries are handled as a safety issue. Treat it today when a western yellowjacket nest sits under a deck stair, beside a door or under the patio in Aurora or Colorado Springs, because by August thousands of workers are a few feet from daily traffic. Tape the gap, shut the door and get a pro out. A comb in a wall void that has found a gap into a bedroom sends wasps toward lamps each night. Treat it today when wasps are inside the house.
How to compare two wasp quotes in Colorado.
Two quotes that match on nests found, return visits, sealing and removal can be compared on price. check the applicator's license with your state pesticide agency; the EPA and the National Pesticide Information Center both list them. Ask what they do if the colony is honey bees. Ask whether heptyl-butyrate traps are offered for September yellowjacket pressure, and whether that is a separate seasonal service. Are post caps and cavity plugs offered, and at what price? For a hornet nest, is it treated and removed, or treated and left, and does the company recommend waiting for frost on a high nest in October? For a yellowjacket burrow, is the follow-up check and the fill in the price? For a wall void, is there a return visit before sealing, and is the sealing included? Then check the pieces. If one quote names three nests and the other names one, the higher number may reflect a better inspection. A Colorado quote for one comb is rarely the whole job; CSU's list of European paper wasp sites means a thorough pro checks the grill, posts, pipes, rock beds and siding seams and prices what they find. Ask both companies how many nests the price covers and where they looked.
What affects the price
- Nest size and number of wasps.
- Nest location: ground, eaves, attic, or high areas.
- Accessibility: hard-to-reach nests cost more.
- Species: hornet nests may require special equipment.
- Time of year: late summer nests are larger and more aggressive.
- Number of nests on the property.
- Follow-up visits to confirm the nest is dead.
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What is your biggest concern about wasps on your property?
When to call for help
A comb inside the grill or a fence cap, found in spring while it is small, is usually yours to handle. when a bald-faced hornet nest hangs over a path or is above ladder height, and whenever someone in the house has reacted to a sting before, given the American College of Allergy, Asthma and Immunology's finding of a 60 percent chance of a similar or worse reaction the next time. for any western yellowjacket nest in the ground, under a deck or beside a patio, because by September the colony is at full size and scavenging. Call when wasps are going into the wall, since CSU lists hollow spaces behind walls among the European paper wasp's sites and the comb is out of reach of any can.
What you can do yourself
Where DIY stops is the wall and the ground. A comb in the hollow behind siding cannot be reached with spray, and sealing the seam pushes the wasps inside. A western yellowjacket burrow in a Greeley lawn has thousands of workers by August, and the CDC's finding that 84 percent of sting deaths are men lines up with a man on his knees at a burrow with a can. A pro brings dust, a suit, a return check and the option of lure traps. Pay for walls, ground nests and hornets; keep the grill for yourself. Colorado is friendly DIY territory for the European paper wasp, because its colonies stay small. CSU puts a nest at several dozen wasps by the end of summer, and a comb inside a grill, a pipe or a fence cap in Arvada or Thornton can be handled with a long-range aerosol at dusk and a scrape the next morning. In March and April, when CSU says the earliest activity begins, a comb is a single queen and a broom does it. Check the grill, the mailbox, the hose reel and every hollow post before you use them.
Where you live matters
Applicators are licensed by the state agency listed in the EPA and NPIC directories. Housing at a median value near $530,000 is largely newer frame construction with siding over wall voids, grills on decks and fenced yards full of hollow posts, which is a long list of cavities. CSU reports the European paper wasp's first Colorado record from Larimer County, home to Fort Collins and Loveland, in August 2001, and its spread since then covers every urbanized county on the eastern plains, from Greeley and Longmont through Aurora, Lakewood and Centennial to Pueblo, plus Mesa, Montrose and Delta counties around Grand Junction. The median winter low of 18F ends every colony each fall; no nest in the state survives to a second year. Across the 19 cities we track the median summer high is 88F, humidity sits around 50 percent and rain totals about 16 inches, which is why so many yards from Denver to Colorado Springs use rock landscaping and why CSU lists rock cavities among the European paper wasp's favorite nest sites. Colorado wasps live on a short, dry, high calendar.
Simple ways to keep wasps away
- Open the grill, mailbox, hose reel and every hollow post in March, when CSU says European paper wasps first stir, and clear any starter comb.
- Cap fence posts, pipe ends and patio umbrella poles, and plug bell and fixture cavities with mesh or foam.
- Seal siding seams and the gaps behind lights and hose bibs before April to keep combs out of wall voids.
- Rake and reset rock landscaping in spring to close crevices, or accept that boulders will host a comb or two.
- Fill old vole and ground squirrel burrows along the foundation so western yellowjacket queens cannot move in.
- Hang a heptyl-butyrate trap at the lot line in April to catch yellowjacket queens.
- Cover trash, compost and fallen fruit from late August through September.
- Store the grill with the cover on and the hood closed all winter; an open hood is a March nesting site.
Jot down where nests turned up this year. Queens often pick the same eaves and gaps, so you'll know where to look first next spring.Did you know?
Paper wasps build their nests from chewed wood fiber mixed with saliva, creating a water-resistant paper material.
Yellowjackets become more aggressive in fall as natural food sources dwindle, leading them to scavenge near humans.
Bald-faced hornets are actually a type of yellowjacket, despite their name and black-and-white coloring.
Questions people ask
How do I identify a wasp nest?
Look for papery, umbrella-shaped nests under eaves or in shrubs (paper wasps), or gray, football-sized nests in trees (bald-faced hornets). Yellowjackets often nest in ground holes or wall voids. You may see wasps flying in and out of a single opening.
Can I remove a wasp nest myself?
Small, exposed nests can be removed at night using a wasp spray, but risks include stings and incomplete removal. For safety, especially with large or hidden nests, hire a professional.
When is the best time to treat a wasp nest?
Early morning or late evening when wasps are less active. Treat in spring or early summer before colonies grow large. In Colorado, June is ideal for early intervention.
How long does professional wasp removal take?
Most treatments take 30–60 minutes on-site. For dust treatments in walls, full colony die-off takes 1–2 days. A follow-up visit may be needed for removal.
Are wasps beneficial to the environment?
Yes, wasps prey on many garden pests like caterpillars and flies. They also pollinate some plants. However, their benefits usually don't outweigh the risks when nests are near people.
What should I do if I'm stung by a wasp?
Clean the area with soap and water, apply ice to reduce swelling, and take antihistamines for itching. Seek emergency care if you have signs of an allergic reaction, like difficulty breathing or swelling of the face.
What stops people from dealing with wasp nests?
In Colorado, fear of stings, nests that are hard to reach, and not noticing them until they're big.
How seriously do people take wasp problems?
In Colorado, most people act once a nest is near a door, deck or play area, where stings are most likely.
Sources (15)
The facts in this article come from the public sources listed above. Every home is different, so ask the company you talk to about pricing and what’s included. Published by Wasp Exterminator · Updated September 11, 2026 · How we write these guides