When small flies show up in your home, the temptation is to call them all "fruit flies" and start setting out bowls of vinegar. The problem: a vinegar trap doesn't work on drain flies. A bleach treatment doesn't help with fungus gnats. And spraying the houseplant won't fix a kitchen issue.
Three different small flies show up in Guelph homes, and each one tells you something different about where the problem is. Here's how to tell them apart.
Fruit Flies
What they look like: About 3mm long, tan to light brown body, distinct red eyes. They hover around fruit, drinks, and food.
Where they breed: Overripe or fermenting fruit and vegetables, dirty recycling bins, dishrags with food residue, beer or wine residue in cans and bottles, garbage with food.
The lifecycle clue: Eggs hatch in 24–30 hours. A few fruit flies become a swarm in a week if the food source isn't addressed.
How to fix it:
- Throw out or refrigerate overripe produce
- Rinse all recyclables thoroughly
- Clean out garbage cans and recycling bins
- Wipe down counters where juice or beer may have spilled
- Run the disposal with hot water and a degreasing soap
- Set out apple cider vinegar traps — these do work on fruit flies
- Persist for 2 weeks to break the breeding cycle
Drain Flies
What they look like: About 2–5mm long, dark grey or black, fuzzy-bodied, with patterned wings. They look more like tiny moths than flies. They're slow, weak fliers and tend to rest on walls and ceilings near the drain they came out of.
Where they breed: Slimy organic buildup in drains — kitchen sinks, bathroom sinks, floor drains, shower drains, basement drains. They breed in the gelatinous bacterial film that builds up on the inside of drain pipes.
The lifecycle clue: They emerge directly from drains. If you tape a clear plastic bag over a drain overnight and find flies stuck to the inside in the morning, that drain is the source.
How to fix it:
- Forget about pouring bleach down the drain — it doesn't reach the slime
- Use a drain brush or pipe cleaner to physically scrub the inside of the drain
- Pour boiling water down the drain after scrubbing
- For floor drains and harder-to-reach drains, an enzymatic drain cleaner specifically designed for organic buildup is more effective
- Repeat over several days
- For persistent issues, professional drain treatment with industrial enzymes is the most effective approach
Fungus Gnats
What they look like: Tiny (2–3mm), thin, dark grey or black, with long legs. They look more like miniature mosquitoes than flies. They tend to hover around houseplants or hop along soil surfaces.
Where they breed: Wet potting soil in houseplants, particularly overwatered plants or plants with constantly moist top layers of soil. The larvae feed on fungus and organic matter in the soil.
The lifecycle clue: They live around plants. If the flies appear primarily near your houseplants — and especially if you've noticed them rising up when you water — that's fungus gnats.
How to fix it:
- Let the top inch of soil dry between waterings
- Use yellow sticky traps near plants to capture adults
- Apply Bti (Bacillus thuringiensis israelensis) products like mosquito dunks to the soil — kills larvae without harming plants
- Repot heavily affected plants with fresh, well-draining potting mix
- Reduce overall watering until the problem clears
- Bottom-water plants instead of top-watering during the infestation
The Comparison Table
Quick reference:
FeatureFruit FlyDrain FlyFungus GnatWhere they're seenKitchen, near foodBathroom, near drainsHouseplantsBodyTan, smoothDark, fuzzyDark, thinFlightQuick, hoversSlow, weakSlow, hoppingBest trapApple cider vinegarDrain scrubbing + enzymesYellow sticky + BtiSource to addressFood/garbageDrainsWet soil
Why Misidentification Costs Time
Each species needs a different approach. Common mistakes:
- Setting out vinegar traps for drain flies (no effect)
- Pouring bleach for fruit flies (doesn't address the actual source)
- Treating drains for fungus gnats (the flies aren't from there)
- Killing visible flies without finding the breeding source
A vinegar trap can catch hundreds of fruit flies and the population still doesn't go down — because every adult you trap, ten more are being laid in the unaddressed source. The fix is always upstream.
When to Call a Pro
Most small-fly problems are DIY territory. Call for help if:
- You've identified the source and treated it, but the problem persists
- You suspect a deeper drain or sewer line issue
- Fungus gnats are spreading across many plants
- Fly populations are large and you can't locate the source
- You're dealing with a commercial space (restaurant, café, food prep facility)
Professional treatment can include drain-line treatments with industrial enzymes, source-tracking inspections, and targeted treatments where DIY isn't reaching the population.
How Summit Handles Small Flies
For small-fly problems in Guelph and KW, Tateum's approach starts with identification — which species, and where it's actually breeding. Treatment depends entirely on the source.
For drain flies, professional enzymatic drain treatments and source inspection often resolve the issue. For fruit flies in commercial spaces, source elimination plus residual treatments in non-food areas. For fungus gnats, the focus is on environmental control and Bti applications.
Frequently Asked Questions
Are small flies a health concern?Fruit flies can carry bacteria from contaminated surfaces to food. Drain flies and fungus gnats are mainly nuisance pests with minimal direct health impact, though they can be allergens for some.
Why does my fruit fly problem come back every summer?Warmer weather speeds up reproduction, and summer produce in the kitchen creates more breeding sites. Tighter food storage and recycling habits in summer can prevent it.
Can I get fungus gnats from store-bought soil?Yes. Commercial potting soil sometimes arrives with fungus gnat eggs or larvae. Letting the soil dry between waterings prevents the population from establishing.
Do ultrasonic devices work on small flies?No reliable evidence that they do. Save your money.
Identify First, Then Treat
The 10 minutes you spend figuring out which species you have is the difference between solving the problem in a week and chasing it for months.
Summit Pest Control offers small-fly identification and treatment across Guelph, KW, Cambridge, and surrounding areas — including drain treatments and commercial food-prep environments.
Call (226) 780-6446 or request a quick estimate today.