A factory with silos from above and a distance away


It’s important for food processors to understand the differences between fly species so that they can more quickly solve any potential issues. Whether the flies you’re dealing with are large or small, here’s what your pest professional is looking for in order to keep your facility fly-free and audit ready.

Small Flies

Small flies may seem like just a nuisance but they are actually a more common problem in food processing facilities than large flies. Additionally, large flies are usually in a facility as an incidental invader whereas small flies more commonly develop inside the plant, pointing to a larger sanitation issue that needs to be resolved.

Fruit Flies. Fruit flies are the most common of the small flies. They seek out sugary, malty or vinegar-type materials like soft drink dispensers, beer taps, over-ripe fruit or fruit wastes, trash cans or vending machines with product residues.

Phorid Flies. Phorid flies have a distinctive humped back and small head. They infest everything from food wastes, sewage, dead animals, feces and other moist organic material. Phorid flies can infest resources deep underground, such as cracks and crevices where wash water or mops continually feed organic material.

Drain Flies. Drain flies are small, fuzzy flies that resemble a moth. Unlike other flies, drain flies are not strong fliers and tend to spend their time in moist, slime-filled cracks, crevices and drains.

Small Dung Flies. Another drain-goer, the small dung fly resembles a miniature house fly. They are often found in areas with decaying materials.

Large Flies

Unlike small flies, large flies tend to be incidental invaders in a facility. Different types of large flies indicate different problems, so property identification is critical in remedying the situation. For example, large flies found indoors during cold months could be developing on rotting food sources that need to be cleaned. Cluster flies aren’t necessarily attracted to food – they are more likely to enter through cracks and crevices in the building. Once you know the large fly species, you can begin to resolve the issue.

Want this information and more for your team? Download our full PDF resource on Fly Management