How to Get Rid of Mosquitoes in Korea (And Why October Is Worse Than July)

Korean mosquitoes are worse in October than in July, and it is not your imagination. Seoul's own trap data puts 54.3% of the year's mosquitoes in September, October and November — October alone brings in roughly twice July's count. Extreme summer heat actually suppresses them, and they surge back the moment it cools. The fix is not a better spray: it is closing the four routes they use to get into a Korean apartment, and the whole lot costs about ₩11,000 at Daiso. We do this across twenty share houses in Seoul every year, so what follows is the order that actually works.

What you need before you start

Everything here is at Daiso. Prices are from Daiso Mall, checked 10 September 2026.

A screen patch, one drain trap and a pack of mats is ₩9,000 and covers most apartments. Add a second trap if your kitchen and bathroom drains are separate.

Why does the season peak so late?

This is worth understanding, because it tells you when to bother.

Mosquitoes thrive at around 26 to 27°C. Above 33°C their survival time can shrink to about a week, and as Professor Lee Dong-kyu of Kosin University puts it, at very high temperatures they conserve energy and refrain from flying. Heavy summer rain compounds it by washing larvae out of the standing water they breed in.

So during a Korean heatwave they are not gone — they are sheltering in cool, damp underground drainage. When the temperature drops into their comfort band, they come back up all at once. Autumn is also their spawning period, so the females feed harder to fuel egg-laying.

The Seoul Research Institute of Health and Environment's trap data shows the shift plainly. Between 2015 and 2019 the annual peak fell in July or August. Since 2020 it has landed in September, October or November — the latest on record being November 2022.

How do you actually mosquito-proof a Korean apartment?

Do these in order. Each step closes a route, and closing routes beats repelling what is already inside.

1. Check the 방충망 in daylight, from inside

Stand inside with the light behind the screen and look for pinholes, a corner lifted out of its channel, or a gap where the screen panel does not overlap the frame.

Expected outcome: you will find something. Screens in older villas are usually a few years past their life, and the failure is normally at a corner rather than in the middle.

Common pitfall: people check the big window and forget the small bathroom or kitchen one, which is the one that gets left open. Check every screen in the unit.

2. Patch it — do not replace it

Tape at ₩2,000 or patches at ₩1,000 handle almost everything. Cut generously past the tear, press it flat from both sides.

Expected outcome: a repair that holds a season. This is a landlord-safe fix — nothing is drilled and nothing is removed.

Common pitfall: taping over a screen that has come out of its rubber channel rather than pushing it back in first. If the whole edge has lifted, seat it again before you tape, or you will be taping air.

3. Fit a drain trap in the bathroom and the kitchen

This is the step almost nobody does and the one that matters most in autumn. A ₩3,000 silicone trap sits in the drain, opens under running water and seals shut afterwards.

Expected outcome: the route they use during heatwaves is closed. It kills the drain smell too, which is a fair trade for three thousand won.

Common pitfall: buying the wrong shape. Bathroom floor drains and sink drains take different traps — check the drain diameter before you go, or buy the five-flap 하수구 냄새 차단 트랩, which is more forgiving.

4. Seal the aircon pipe hole

In older villas the hole drilled through the wall for the air-conditioner drain pipe is often packed with nothing but a scrap of foam, or left open.

Expected outcome: one less permanent opening straight into the room.

Common pitfall: sealing it with something rigid that traps water against the wall. Use a flexible filler or putty, and leave the drain pipe itself clear.

5. Only now, run a vaporiser

With the routes closed, a 홈매트 mat in a plug-in vaporiser is genuinely effective in a shut bedroom. One mat runs about 15 hours, and the 45-pack at ₩5,000 covers a full season.

Expected outcome: an undisturbed night.

Common pitfall: running it with a window open for air. Choose one or the other, or you are venting the vapour and inviting the mosquito in the same motion.

What works, and what people buy that does not?

The pattern is that everything people reach for first is a repellent, and everything that actually works is a seal.

What if you are renting and cannot modify anything?

Every fix above is reversible. Screen tape peels off. Drain traps drop in and lift out. A vaporiser unplugs. Nothing here needs a landlord's permission or leaves a mark, which is deliberate — most people reading this are in a room they do not own.

If your screen is beyond patching, that is a repair request rather than a purchase. In a properly managed building the screen is the landlord's responsibility, and asking is reasonable. Our guide to what fully furnished actually means in Korea covers where that line usually falls.

Should you worry about disease?

Malaria exists in Korea at low levels, concentrated near the northern border, and Seoul steps up autumn malaria prevention as temperatures cool. Japanese encephalitis advisories are issued seasonally too.

For most residents in Seoul the honest answer is that the risk is lost sleep, not illness. But bites plus fever is a doctor's visit, not a wait-and-see.

Where does this fit in a first year in Korea?

Mosquitoes are one of a set of small domestic things nobody briefs you on before you arrive — along with the bins, the heating bill and what the drain smell in August means. Our first 30 days in Seoul checklist covers the arrival admin, and living in Seoul day to day covers the rest of the domestic learning curve.

We run furnished share houses across Seoul, and screens and drain traps are part of what we maintain rather than something a tenant inherits and discovers in September. If you would rather that were somebody else's job, tell us what you need.

Sources

Checked 10 September 2026. Daiso prices move — treat them as approximate after this date.

• Seoul Research Institute of Health and Environment trap data, via The Korea Times, warming climate extends Korea's mosquito season beyond summer — the 54.3% autumn share, the July and October counts, the seasonal shift since 2020, and the temperature thresholds
• Seoul 모기예보제 open data — the city's Digital Mosquito Monitoring System dataset
• Daiso Mall product pages: 보수용 방충망 테이프, 홈 매트 45매입, 하수구 냄새 차단 트랩, 욕실용 배수구 트랩, 원형 전기 모기채