The dog days of summer are here. For food processing facilities, that means that issues with flies are likely on the rise. These buzzing pests are more than just an annoyance—they spell danger. By understanding how flies operate, you can take action to reduce or even eliminate them at your facility.
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Explore This IssueJune/July 2015
Flies have very clearly been associated with disease causing organisms: E. coli, Salmonella, Staphylococcus, and more. Every time a fly lands, it is potentially spreading these dangerous bacteria, contaminating the food you produce and your equipment. Depending on where in the process that contamination occurs, the presence of flies could be putting people who eat that food at risk.
And while contaminated food and equipment is certainly the largest concern that flies pose to food processors, there’s another danger that flies can pose for processing facilities. Third-party audits and regulatory compliance are placing an increased focus on risk-based pest management programs. Cockroaches, rodents, and other pests food processing facilities often deal with are nocturnal or cryptobiotic, meaning that they like to hide, which makes them less likely to be out in the open during day-to-day operations. Flies are the complete opposite. They are out during the day and actively flying, and that makes them very visible to auditors and regulatory officials. Simply seeing flies might signal a concern about a facility’s entire pest management program.
Flies are more than just an annoyance. They are a real and present danger that needs to be addressed as part of a pest management program for a food processing facility.
The Science Behind Your Fly Problem
For food processing facilities, the most likely culprits for fly issues will be house flies, blow flies, and on occasion, bottle flies.
Adult house flies can live for up to 25 days—more than enough time for a single female house fly to produce a virtual army of flies. In her lifetime, she can lay between 350 and 900 eggs. Adult females of other filth fly species can wreak even more havoc; blow and bottle flies can produce as many as 2,300 eggs. Simple math will show you how quickly a relatively small fly issue can become a major problem for a processing facility.
Flies are attracted to mainly two things: heat and odors. Heat signals optimal living and breeding conditions, and odors draw them to potential food and breeding sources.
Food processing facilities naturally generate heat through the use of machinery. If heat is escaping through gaps, cracks, windows, and doors, it may be attracting flies toward your facility. Remember, a fly’s sole purpose in life is to reproduce; the optimal temperature for egg production is between 77 and 86 degrees Fahrenheit, so flies will seek out that temperature range. If your facility handles livestock or poultry, you may also be generating heat through the presence of animals and their manure.
Odors that are both good and bad to humans can be fly attractants. Flies have an extraordinary ability to detect these odors from great distances. While most house flies will fly about a mile to find food and breeding sources, they have been shown to be able to detect odors from as far as five miles away.
Think about what is in a five-mile radius of your facility. If your operation produces any odor that is attractive to flies, they can find their way from naturally occurring breeding sites, sewage treatment plants, farms, and even something as small as the carcass of an animal on the side of a road.
Using an Integrated Approach
Integrated pest management (IPM) is not a new concept to most processing professionals. The most effective way to resolve most pest issues is to use a variety of control or elimination methods. It’s no different for flies. By using what we know about fly biology, facilities can use a combination of tactics to reduce and eliminate fly issues.
Reduce fly attractants. The best way to solve a fly issue is to get rid of the things that are attracting flies. By working with your pest management provider, you can identify what on your property may be attracting flies. For most facilities, a fly problem on the interior isn’t likely. When it comes to breeding, large flies need very decayed organic matter to be successful. The odors created by these breeding sources are usually very strong, putrid smells—decaying animal carcasses, rotting organic materials, etc. Most often, these breeding sources will be outdoors.
If the breeding source is on your property, remove it. If it is not possible to remove it, your pest management provider can discuss with you ways to contaminate that breeding source to make it uninhabitable to flies.
If you’ve never had a fly issue before and one suddenly develops, your pest management provider may ask you questions about recent changes in process to see if there’s something new that could be attracting flies.
In many cases, the entire fly breeding source may not be on a facility’s property and flies may be attracted to your facility from other areas. In these cases, removing the breeding source may not be an option, so setting up a defensive perimeter is your next course of action.
Engineer your facility to fight flies. In combination with reducing fly attractants, putting measures in place to prevent fly entry into a facility is critical. For most processing facilities, the highest risk of fly entry can be found at receiving areas where livestock may be brought in or product spillage is occurring.
On the interior, preventing fly entry can be as simple as installing door sweeps, screens, air curtains, or plastic strip doors. Educating employees to keep exterior doors closed when not in use can also go a long way toward keeping flies out. Installing a gauntlet of insect light traps and other fly traps is another way to catch flies before they enter critical processing areas.
Engineering your facility to fight flies. may also mean working with your facility’s engineering team to reduce the amount of air escaping through door seals, window frames, and other openings. This reduces heat that may be attracting flies to your facility.
In addition, when possible, ensure that your facility has positive air pressure. What is positive air pressure? We’ve all experienced it—when you open the door to a building and feel air pushing back out at you. Positive air pressure works to deter flies because flies can’t or won’t fight against the air current escaping to enter the facility. Changing the air pressure of a facility may simply not be possible, however, if it is a core problem with the facility’s HVAC system.
Odor management systems. Many facilities may be able to drastically reduce or even eliminate fly issues by addressing odor issues. When used as part of an IPM strategy, odor management technology can be an effective way to deter pests from a variety of operations. At one time, food processing facilities needing odor management systems had to invest in expensive equipment that was messy and required ongoing maintenance. Today, there are alternatives available that are compact, cost-efficient, easy-to-maintain, and utilize environmentally friendly odor neutralizers that work to eliminate odors, rather than just mask them.
Positive air pressure works to deter flies because flies can’t or won’t fight against the air current escaping to enter the facility.
Fly baiting programs. Utilizing fly baits has proven one of the most effective ways to deter flies from a facility. However, traditional scattered/broadcast granular fly baits can be problematic in processing environments where loose baits can contaminate product when they are inadvertently spread by foot and vehicular traffic.
Pheromone-based fly baiting is an ideal solution. Granular fly bait containing pheromones can be strategically placed in bait stations around the facility so that flies are attracted to the stations before they reach openings in your structure. These stations also dramatically reduce the possibility of product contamination with loose bait. These newer fly bait formulations are considered much more attractive than their older cousins and use different active ingredients to kill the flies.
Parasitic wasps. It may sound like something out of a futuristic horror movie, but parasitic wasps are actually a very effective and truly green form of pest management that can significantly crush fly populations. These tiny, sterile, non-stinging wasps have a short life cycle with a singular mission: to reproduce. Unfortunately for flies, parasitic wasps depend on fly pupae to do that.
A pest management professional can install parasitic wasp release stations at strategic points on your property. Once they are released, these wasps begin to hunt out fly pupae in which to lay their own eggs. The wasp uses its non-functioning stinger to break into the fly pupae and lay its eggs. When the wasp egg hatches, it feeds on the immature fly. In doing this, the wasps prevent new flies from becoming adults.
You’ll need to work with a pest management professional to set up a parasitic wasp program as the wasp life cycle is short and populations will need to be refreshed periodically.
There’s no silver bullet to fly problems. Fly issues will be unique at every facility depending on the products being produced, processes being used, and environment surrounding the facility. To best protect your facility, work with an experienced pest management provider to address the specific risks present at your facility. This integrated, custom approach to fly problems will ensure that your facility is compliant with audit standards and, most importantly, the product you are producing remains safe from potential contamination.
Black is a board certified entomologist and vice president, technical services for The Steritech Group, Inc. She received her MS in Entomology and her BS in Agriculture from West Virginia University and has nearly 30 years of experience in the pest management industry. Reach her at firstname.lastname@example.org.