The short version
Around Fort Collins, flies are busiest from about April into October. Find their source: trash, drains, compost or a dead animal. Remove it, then seal gaps and screens.
- Flies breed in something nearby.
- Check trash, drains and compost first.
- Tape a drain overnight to test it.
- Big shiny flies can mean a dead animal.
- Screens and door sweeps keep them out.
Anyone in Fort Collins who wants flies out of the house.
What to look for
Flies don't come from nowhere. They breed in something nearby. In summer heat, eggs become adults in about a week. Spraying the flies you see won't stop new ones.
- 1Flies gathering at sunny windows.
- 2Tiny fuzzy flies near sinks and drains.
- 3Shiny green or blue flies indoors.
- 4Maggots in trash bins.
- 5Flies around compost or pet waste.
- 6A sudden bad smell with flies.
Why it’s worth acting soon
- Flies carry germs onto food and counters.
- Populations grow fast in warm weather.
- A dead animal smell gets worse.
- Cluster flies return every fall.
Treatment options and typical costs
Source Inspection and Fly Identification
$75–$200
Expect a pro in Fort Collins to check drains, trash areas, pet waste, compost, floor drains and any spot where a dead animal could be hidden. The adults you see are only the symptom.
- Time
- 45–90 minutes
- Best for
- Every job; the species points to the breeding site
Sanitation, Source Removal and Drain Bio-Cleaning
$100–$350
Sanitation is shared. The pro treats and points out fixes; you keep it up. Expect a short written list.
- Time
- 1–3 hours
- Best for
- House flies, drain flies, fruit flies; the fix that lasts
Light Traps, Baits and Residual Resting-Surface Treatment
$150–$450
A pro should explain that adult control alone is temporary. If the source is not fixed, traps simply refill.
- Time
- 1–2 hours
- Best for
- Knocking down adults while sources are fixed
Exclusion: Screens, Door Sweeps and Air Curtains
$150–$450 (air curtains more)
Restaurants and shops in Fort Collins often add air curtains over delivery doors and back entrances. A properly sized unit pushes flies back whenever the door opens.
- Time
- 1–4 hours
- Best for
- Buildings with steady fly entry from outside
Prices are typical published ranges. Ask what’s included before you compare quotes.
Drain flies breed in the slime inside drains. A stiff brush and an enzyme cleaner clear it.Which flies show up around Fort Collins.
Fungus gnats hover around overwatered houseplants. They show up at windows on warm days. Cluster flies hide in attics and walls around Fort Collins for winter. A sudden swarm often means something died nearby. Blow flies are shiny green or blue. They breed in the slime inside drains. Drain flies are tiny and fuzzy. They breed in trash, compost and manure. House flies are the most common around Fort Collins.
Local flies conditions in Fort Collins.
A provider who works Fort Collins and Colorado every day can point out the specific conditions that matter most here, and getting the scope, price, and follow-up terms in writing makes it easier to compare options. Knowing Fort Collins's seasonal timing lets you schedule treatment before the busy stretch rather than after it, which usually means faster service and a more accurate quote. An inspection in Fort Collins usually starts outside and works inward, checking the foundation, gaps around doors and windows, and any moisture or clutter near the structure first. Around Fort Collins, the area is mostly urban, so flies pressure can differ from one block to the next depending on how tight the entry points are and how much food, water, or shelter is close by. Fort Collins sits in a semi-arid climate, and that sets the pace for fly activity here: spring through fall; cluster flies overwinter indoors.
Trash bins are the top source in summer. Keep lids closed and rinse bins every week or two.Fly season in Fort Collins.
Numbers peak in mid to late summer. Cluster flies move into walls in fall. Seal gaps before September.
Finding the source.
From Fort Collins out to Loveland and Greeley, trash bins in summer are the usual culprit. Likely a dead animal. Bad smell plus big shiny flies? Flies stuck to it mean the drain is the source. Tape over a drain overnight. Check trash bins, recycling and compost first. Watch where flies gather and where they're coming from.
A year of flies in Fort Collins.
- Spring: flies return. Check screens. - Summer: peak season in Fort Collins. Empty trash twice a week. - Fall: cluster flies look for a way in. Seal gaps. - Winter: fix screens and doors.
Which fly is it?
- House fly: gray, a quarter inch, everywhere. - Drain fly: tiny, fuzzy, moth-like wings. - Blow fly: shiny green, blue or bronze. - Cluster fly: big, slow, golden hairs. - Fungus gnat: tiny and black, near plants. - Fruit fly: tan with red eyes, near ripe fruit.
Cleaning a drain fly drain.
- Scrub: run a stiff brush down the drain. - Enzyme: pour in an enzyme drain cleaner at night. - Repeat: do it daily for a week. - Check: tape over the drain to see if flies still emerge. - Skip: bleach alone doesn’t clear the slime.
Keeping flies out.
- Screens: patch holes in windows and doors. - Sweeps: add door sweeps to exterior doors. - Trash: keep lids closed and rinse bins. - Compost: cover it and keep it away from doors. - Pets: pick up waste daily.
Fly traps that actually help.
- Sticky ribbons: fine for garages and sheds. - UV light traps: best for kitchens and businesses. - Bait traps: hang them outside, away from doors. - Swatter: still works for a few strays. - Skip: bug bombs. They don’t reach the source.
If something died nearby.
Follow the smell and the flies. Wear gloves, bag it, and disinfect the spot. A wall may need a small hole opened. The flies stop once the source is gone.
Flies and pets.
Pet food and waste draw flies fast. Pick up food bowls after meals. Clean up the yard daily in summer. Flies biting a dog's ears are usually stable flies. Ask your vet about protection.
Flies at a business.
Restaurants and food businesses need a steady routine. Seal dumpsters and clean them weekly. Use air curtains or strip doors at busy entries. Schedule drain cleaning and regular service visits.
Flies and food safety.
Flies land on trash and then on food. Cover food outdoors and wipe counters often. Throw out food flies have landed on for long. Keep fruit in the fridge in summer.
What a fly visit looks like.
The tech looks for the source first. They check trash areas, drains, attics and gaps by doors. Then they clean, seal or treat what they find. Traps help confirm the problem is gone.
Screens and doors.
- Screens: patch holes and check the corners. - Doors: add sweeps and keep them closed. - Patio doors: a screen door helps in summer. - Fans: a fan by the door keeps flies moving on.
Compost and yard waste.
Flies breed in wet, rotting material. Keep compost covered and turn it often. Bag clippings. Pick up fruit and pet waste every few days.
Trash day habits.
Bag food scraps tightly before they go in the bin. Rinse bins every couple of weeks in warm weather. Keep lids shut and park bins away from doors.
Questions to ask before you sign.
- What kind of fly is it? - Where are they breeding? - What will you clean, seal or treat? - Are follow-up visits included? - Is dead animal removal extra?
What affects the price
- Whether a dead animal must be located and removed.
- Number of drains needing bio-cleaning.
- Fly species and where it breeds.
- One-time visit versus monthly service plan.
- Home versus restaurant or multifamily building.
- Travel distance and local labor rates.
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What bothers you most about flies?
When to call for help
Call if you can't find the source after a few days. if you smell something dead in a wall. if cluster flies come back every fall. Businesses usually need regular service.
What you can do yourself
Most home fly problems are DIY. Find the source and remove it. Clean drains, rinse bins and fix screens. A pro helps with hidden sources, walls and attics.
Flies in Fort Collins
In denser parts of Fort Collins, dumpsters, alleys and restaurant trash are the big sources. With about 16 inches of rain a year, damp spots around Fort Collins also breed small flies. Summer highs near 87°F in Fort Collins speed up the fly life cycle, so trash and compost need extra care.
Fly tips from the experts
Where are the flies coming from?
The kind of fly tells you where to look. Around Fort Collins, Colorado, note its size, where it gathers and when it shows up. Then go after the source.
Small flies near drains
Tiny, fuzzy flies near a sink or shower usually breed in the slimy film inside the drain. Scrub the drain with a stiff brush. Spraying the adults won’t stop them.
UC IPM: drain fliesHouse flies around doors and trash
House flies breed in garbage, pet waste and rotting plants. Clear those out first, then add screens and keep doors closed. Traps help, but they don’t fix the source.
EPA: managing fliesSlow flies at the windows in fall?
In colder states like Colorado, sluggish flies at upstairs windows in fall, winter or early spring are often cluster flies. They spend winter in attics and walls but don’t breed indoors. Sealing gaps outside in late summer keeps them out.
University of Minnesota Extension: fliesBased on guidance from university extension services and the EPA.
How we check our sourcesLocal research
Flies in Fort Collins, CO: what the public record shows
Before you compare quotes, it helps to know which flies actually live in Colorado, when they are busiest around Fort Collins, and what the state figures look like. Everything below links to the agency or university page it came from.
Most common fly in Colorado homes during cool months
Flies appearing indoors in fall and winter in Colorado are usually overwintering cluster flies from the lawn, not a sanitation problem.
Colorado State University ExtensionFly species recorded in Colorado
- House fly (Musca domestica) — Non-biting; breeds in manure, garbage, lawn clippings, decaying produce. 45 days at 60°F to 7 days at 95°F. Carries bacteria and viruses causing diarrhea, cholera, food poisonin…
When flies are busiest around Fort Collins
Cluster flies enter buildings late August–September and reappear on warm winter days; fruit fly numbers peak late summer and early fall.
CSU Extension notes cluster flies are particularly abundant at higher elevations in Colorado; the house fly is not the most common indoor fly in the state.
Sources: Colorado State University Extension; Texas A&M AgriLife Extension; University of New Hampshire Extension; Flies (Home and Landscape). Figures are quoted as the source prints them. How we check our sources
Simple ways to keep flies away
- Keep trash bins closed and rinse them.
- Take trash out often in summer.
- Repair window and door screens.
- Add door sweeps.
- Pick up pet waste daily.
- Clean drains with a brush and enzyme cleaner.
A good quote names the fly, the source, and what will be cleaned, sealed or treated.Did you know?
A house fly generation can take ten days in heat
Drain flies are sometimes called moth flies
Questions people ask
Do flies mean there is a dead animal in my wall?
A bad smell is another clue. Big shiny flies swarming often mean a dead mouse. Sometimes.
What are the tiny flies in my houseplants?
Yellow sticky cards help. Let the soil dry out between waterings. Usually fungus gnats.
How do professionals get rid of flies?
They find the source first. Then cleaning, sealing, traps and, if needed, a targeted treatment.
Can flies come from my neighbor's property?
Your own trash and compost still matter most. House flies travel a mile or more. Yes.
Why do I suddenly have big shiny flies in my house?
Around Fort Collins, a sudden cluster of shiny blue or green flies often signals a dead animal in a wall or attic: Bertone and colleagues found blow flies in 48% of 50 North Carolina homes in 2012. Treat it as a rough guide, not a local count.
Are drain flies common in houses?
Yes. Around Fort Collins, the fuzzy little flies on a bathroom wall are drain flies, and they are ordinary: Bertone and colleagues found them in 74% of 50 North Carolina homes in 2012.
Are cluster flies common in Fort Collins?
Yes, they're a fall and winter nuisance around Fort Collins. Seal gaps around windows and siding before September.
When is fly season in Fort Collins?
Flies are busiest from about April into October. Cluster flies also appear at windows in winter.
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Sources (12)
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 Fly Exterminator · Updated September 11, 2026 · How we write these guides