Abundance of House Flies

As we venture in and out of buildings be might have a piggy-backer, the house fly (Musca domestica) joining us indoors. This fly is not only a big nuisance insect, but it can sometimes carry other organisms that can cause diseases in humans and domestic animals. This makes suppressing house fly populations very important.
House flies are ¼-inches in length, light grey in color and have four longitudinal black stripes on their thorax. They also have a pair of large, red-brown compound eyes and sponging mouthparts, so they are non-biting flies.
Adult house flies live up to three weeks and are active during warmer weather. The adult female flies deposit eggs in clusters of 50 to 100 within a variety of moist, decomposing organic substrates including animal manure, accumulated grass clippings, garbage, spilled food and animal feed. The eggs usually hatch into larvae within 12 hours. The larvae then feed on the decomposing organic material as they continue to grow in size. Then the larvae will stop feeding and migrate to drier substrates to pupate. Adult flies will emerge within three days to four weeks, depending on the temperature.

Some Suggestions for Control:

Non-Chemical Control Options:

Frequently clean surfaces and properly dispose of food and other organic materials within a sealed garbage bag. Garbage containers should be closed and placed away from doors to prevent fly breeding and entering buildings. The garbage container should be cleaned a couple of times a month with soap and water to decrease amount of accumulated organic matter. Make sure that windows screens and screen doors do not have holes in order to minimize house fly access. Retail buildings can install air curtains above exterior doors to make it harder for flies to enter. Several types of traps are available that do not contain toxic chemicals, such as sticky traps and ultra-violet light traps. All traps need to be placed at least 5 feet away from food processing areas to avoid contamination. Sticky traps need to be replaced frequently as they loose their effectiveness with time. In addition, a fly swatter can be used to kill the occasional invader!

Some Chemical Control Options:

Chemical control should not be the only control option used, since the overuse of insecticides may lead to secondary problems such as insecticide resistance and increased allergies and other health problems. Some house fly insecticides are sold as aerosol sprays or bait formulations and can be applied to such areas as dumpsters. Several insecticidal sprays labeled for house fly control in and around buildings contain permethrin, tetramethrin or resmethrin. Fly baits are usually sugar-based and contain a compound that attracts the adult flies. The flies that feed on these baits are then killed after injesting the insecticide.

Photo of house flies, Musca domestica Linnaeus (Diptera: Muscidae), mating. Photo by Dr. Bart Drees, Professor and Extension Entomologist.