Keep These Tiny Pests on Your Radar

Columns - From the Advisory Board

Small flies can cause just as big a problem as their larger cousins. Here’s what to look for, and what to do if you spot them.

April 4, 2022

Chelle Hartzer is consulting entomologist at 360 Pest and Food Safety Consulting

For food processing, any insect issue is a problem. Not only is it potential contamination, it’s a reputational issue when it hits the media and people avoid the product. Take the recent news of the recalls at the Family Dollar chain and the recall of Abbott baby formula as examples.

One pest issue that often gets overlooked is small flies. While little, they can cause a mighty problem.

There are three main species of small flies most prevalent in food processing facilities: fruit flies, phorid flies and moth flies. The adults measure about .125 inches (.32 centimeters), and the small size means they are often unnoticed until populations are significantly high. For some reason, they don’t cause the same immediate concerned reaction that German cockroaches, Indian meal moths or even large flies, such as house flies, cause.

Flying blind when it comes to small fly problems is a huge mistake.

The adult flies result in food contamination when they get into foods. While some foods have set defect action levels (DALs) in the United States, consumers have exceedingly high standards. Finding insects or insect parts in food is unacceptable to customers. Small flies can get into food almost anywhere along the processing system.

They could be present in incoming raw ingredients. Small openings in equipment allow them to contaminate the food while in the processing stage. They can also get into the food just prior to packaging and adulterate the final product. There’s even the chance of them getting into packaged products if they are not sealed well.

Small flies can cause just as big a problem as their larger cousins. Here’s what to look for, and what to do if you spot them.

Small flies are an indication of a sanitation problem. The immature stages are living and feeding in moist organic buildup. Drains are a likely culprit, but don’t stop looking there. Spread your wings and look at any location that may have a damp area with food material mixed in. Finding these hidden food resources allows them to be cleaned and the residues removed. By cleaning them, it eliminates the fly larvae at the source. It has secondary benefits as well. By reducing those food resources, it also reduces the chance that other pests may use them and become established. Cockroaches, in particular, like the moist environment and the food.

These insects can carry pathogens as they fly from an infected source to different food and food contact surfaces. Large flies, such as house flies, have long been known to carry pathogens that can cause disease in humans. More recently, small flies have been shown to transfer many of the same pathogens. In a study published in the National Library of Medicine, fruit flies were shown to transmit E. coli, Salmonella and Listeria. They can pick up bits of contamination on their bodies and transfer them from one location to another. In a study published in the Medical Journal of Entomology, moth flies were found to have more than 80 different bacteria on their bodies as well as multi-drug resistant bacteria.

The good news is small flies are relatively easy to control. Finding the sanitation issue and cleaning that is often enough to eliminate small flies. Since the adults do not fly very well, or far, from the source, the sanitation issue is typically close to where adults are seen. Sticky traps and insect light traps are somewhat effective to monitor for small flies; they do have to be close to the source to attract the adult flies. Partner with your pest management team to identify breeding sites and clean those on a regular basis. Since most small flies develop from egg to adult in as little as seven days, cleaning on a weekly basis can have a big impact on reducing small fly populations.

It is important to remember that pest problems occur in food processing. It happens. They have all the items they need for development: food, water and shelter. Having a robust pest management plan in place to prevent insect issues as well as responding quickly when issues do occur can save time, money and reputation. Even the smallest pests, such as small flies, can cause massive problems.

So the next time you see a few small flies, don’t fly off the handle! Start to investigate and eliminate the sources so your facility and its food stays safe.