What causes massive amounts of flies?

Author: Ms. Maud Gibson II  |  Last update: Monday, October 27, 2025

Flies are attracted to many things inside and around your home, especially those derived from fermented or decaying organic matter. Whether it's human food or even something we don't think of as food, such as animal waste or trash.

What causes a sudden infestation of flies?

Decaying matter is one of the most common causes of a fly infestation in and around your home. As mentioned previously, flies are scavengers and eat dead and dying matter.

How do you get rid of a huge fly infestation?

Use cinnamon as an air freshener as flies hate that smell also. Spray house with lavender, eucalyptus, or lemongrass essential oils. Use fans or light candles. Get natural predators like Venus Fly Trap plants. Keep a clean house, kitchen and around and inside garbage cans. Clean up after your pets.

Why are there so many flies outside all of a sudden?

Certain environmental conditions have changed recently, which have become favourable for the flies - maybe an increase in food, a change in temperature and/or humidity, decreased populations of predators in the ecosystem (birds, spiders, etc).

Where are all these big black flies coming from?

Also known as buffalo gnats and several other common names, black flies are true flies found in areas with cool-water rivers and streams. Unlike mosquitoes, which lay eggs near stagnant water, black flies prefer running water. The larvae develop attached to submerged rocks and wood.

How to Get Rid of House Flies (4 Simple Steps)

How do you find the source of a fly infestation?

Most of the time, flies live in organic materials. Check for flies in places like the soil around houseplants or in your trash. They're also commonly found in bathrooms or in areas around or inside drains. You should also check for gaps along your house's foundation, windows, and doors.

How do you get rid of black fly infestation?

The only available effective treatment is a microbial pesticide containing Bacillus thuringiensis israelensis or Bti, which must be metered into the water in weekly treatments during periods of peak black fly activity. These products are also effective against mosquitoes.

Why are flies swarming the outside of my house?

Flies appear in outdoor locations wherever there are food sources and moisture. Dark areas also encourage breeding, while warm areas like open doors or vents attract flies preparing for hibernation. Here are the most common sources of fly infestations outside: Pet waste.

What smell do flies hate?

Cinnamon – use cinnamon as an air freshner, as flies hate the smell! Lavender, eucalyptus, peppermint and lemongrass essential oils – Not only will spraying these oils around the house create a beautiful aroma, but they will also deter those pesky flies too.

What causes flies in a clean house?

Flies get inside for a number of reasons, usually in pursuit of trash, rotting food, or moisture. A common house fly is attracted to decaying organic matter like feces and rotting meat. Drain flies, on the other hand, are attracted to moisture and will lay their eggs inside of drains.

What kills flies quickly?

Use equal parts dish soap and apple cider vinegar, and put the solution in a bowl or jar. Sprinkle sugar on top to further entice the flies. The dish soap will break down the flies and kill them, while the vinegar attracts them.

How long does a fly infestation last?

The entire life cycle of a cluster fly generally takes four to six weeks to complete. However, by invading and overwintering indoors, a cluster fly infestation can persist for several months and continue to be a nuisance until proper removal measures are implemented.

Why do I keep getting big flies?

If you have an uncovered dog food dish or even a dead rat in the wall this will be a fly magnet. Flies can smell rotting meat from several miles away, and since meat is the perfect food for maggots, it's a highly attractive place for flies to come to lay their eggs.

How do you fix a fly infestation?

Here are the 5 most effective natural remedies to get rid of flies:
  1. Make a Rotten Food Trap to Kill Flies. ...
  2. Try the Apple Cider Vinegar and Dish Soap Trap to Attract Flies. ...
  3. Trap Flies with Red Wine. ...
  4. Try to Get Rid of Flies with Essential Oils. ...
  5. Make Use of Fans or Candles.

What is the difference between house flies and cluster flies?

In general cluster flies are slightly larger and darker than your common housefly and tend to move more sluggishly. Adults grow to be 3/8th in length.

What does a swarm of flies mean?

Though flies can be attracted to your home by a variety of factors, such as stinky garbage, leaky pipes, or rotting food, a swarm of flies, particularly blow flies, could be an indication of a gas leak.

Does Pine-Sol keep flies away?

Create a fly and wasp repellent.

This DIY pest repellant should be a staple in the Southern home. Pour equal parts water and Pine-Sol in a spray bottle to spritz on outdoor furniture, the deck, and indoor areas where flies are most likely to flock, such as kitchen countertops.

What are flies most afraid of?

Afraid of shadows

Gibson and his team enclosed flies in an arena where the buzzing insects were exposed repeatedly to an overhead shadow. The flies looked startled and, if flying, increased their speed. Occasionally the flies froze in place, a defensive behaviour also observed in the fear responses of rodents.

What can I put down to keep flies away?

Homemade fly repellent spray: A mixture of dish soap, water, baking soda, and vinegar can be filled into a spray bottle. The mixture should contain a few drops of dish soap and a tablespoon each of vinegar and baking soda per cup of water. A few sprays of this mixture can be an effective fly repellent.

Why is my house full of flies all of a sudden?

Flies can emerge from several sources including food that's been left out, garbage that needs to be taken to the curb, windows or doors left open, and even as larvae in new houseplants. Drains are a common culprit, too, if water is rarely turned on in a sink or shower.

How to find the source of a fly infestation?

Trash cans, dirty diapers, dirty dishes, rotten foods, food debris, etc. are possible breeding areas for inspecting House Fly activity. Most of the time, when you find house flies inside, it is because they are coming inside the structures. Check cracks around windows, doors, and vents as possible entry points.

How to get rid of flies in the house quickly without vinegar?

Mix one cup of water and one teaspoon of cayenne pepper in a misting bottle and spray it near entryways and wherever you see flies. Other natural fly repellents include lemongrass, peppermint, eucalyptus, camphor, and cinnamon.

What is the best killer for black flies?

Apply Bacillus thurengiensis israelensis (Bti) to egg-laying sites in the form of Mosquito Dunks or Aquabac (for large application areas). Bti is a bioinsecticide used for larval control of black flies. Larvicides like Bti should be applied throughout the season when black flies are active for best results.

What causes a lot of flies outside?

There are a handful of reasons why there are so many flies in your yard, and it's usually easy to pinpoint which one is your problem. In general, flies swarm to wet organic material, ranging from what you're cooking on the barbecue to an unsealed garbage can.

What do drain flies look like?

Drain flies are very small, measuring between ⅙ and ¼ of an inch long. They have small, hairy bodies that are brown-gray or black that have a fuzzy appearance. Their wings are also hairy and shaped like leaves. When a drain fly is at rest, the wings sit over the body like a roof for protection.

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