Pests can run, crawl, fly and hitchhike their way into the facilities we service. Some paths are obvious like a door which is left open or poorly sealed, and some not so obvious. Here is a list of the ways pests can enter a building and the methods for preventing entry:

1. Dumpster Compactors. Not only can dumpster compactor chutes provide entry points through poorly sealed chute designs, but the dumpsters themselves can attract and serve as breeding sites for pests. In fact, the dumpster box could be transporting pests to and from the waste disposal site depending on how the box is handled. If the garbage is merely emptied and the receptacle is not cleaned, fly maggots and other insects can continue to thrive inside the residues left behind. If the old dumpster is dropped at the waste disposal site and a new box delivered, it can bring pests with the recycled dumpster. This is one of the reasons that monitoring this area is so important to make sure that rodents or insect pests are not being transported to the site. Facilities should have a program in place for cleaning dumpsters, and dumpster pads, especially during the warm weather months, and sealing around dumpster compactor chutes to prevent pest entry.

2. Trailers And Totes Held For Animal Feed And Farms. Though a great way to reduce the amount of food waste going to landfills, holding food for animal feed can potentially provide a path for pests. Traditionally, feed trailers are not routinely cleaned, which means that residues inside the trailer after loads are dumped can support pests. If the food waste is dry, it could provide an area for stored product pests to develop. If the food waste is moist and organic, filth flies can breed. These trailers may be transported to sites which are less sensitive to pests and whose on-site sanitation is even more poor. We have traced more than one rodent infestation in a food plant to the handler of feed totes. In one case, mice were brought into the facility on the totes. In another example, rats were introduced to the site via trailers returning the totes.

3. Employees. Several urban pests are excellent at hitchhiking. These include the German cockroach and the common bed bug. We routinely find that when these pests inhabit workplaces, they arrive on the belongings of employees. Having a separate area for employees to store their belongings, including lunches, is critical. Monitoring these areas for pest activity is also important with regularly scheduled employee locker clean-outs as a part of the monitoring and inspection process. Facilities should have a policy in place to deal with employees who have been found to be the sources of pests such as bed bugs. These policies should be established prior to the first incident because it will require the involvement of multiple departments, including human resources, when a situation is identified. A timely response means having the action plan in place well in advance.

4. Trailers Used For Pallet And Cardboard Storage. It is not uncommon for facilities to use a trailer to store pallets or other items as a way to increase warehouse storage space. However, often, it is difficult to completely seal around the warehouse door frame/trailer door junctures to exclude pests. Often these doors are left open to allow forklifts easy access to the stored items. Unfortunately, it also provides easy access for pests. These gaps, particularly along the base of the trailer, can be six or more inches wide. Most food facilities would not allow a 6-inch wide gap in a warehouse wall, yet they allow these imperfect seals around storage trailers. These trailers are an extension of the warehouse when used for routine storage. The use of trailers with roll-up doors tends to provide a slightly better seal against the dock than trailers with double doors that swing open. The double doors on the trailer create additional space between the dock and trailer and should be avoided when possible. The best remedy is to keep the dock doors closed while not in use.

5. Incoming Shipments. Just like pests can hitchhike on employees, pests can also hitchhike on raw ingredients and other materials coming into the building. A good inspection of incoming goods is required to make sure any unwanted guests are excluded. Once the product has been accepted into the site, it can be difficult to establish responsibility for the pest infestation. An infestation also can go unnoticed until populations have reached critical numbers. A good example of this issue is pallet mice that can be harboring in the center of a palletized product stack. Pallet mice can remain inside that stack where food is available and begin to infest neighboring products. Numbers can build up quickly and compromise food safety. A proper inspection program can help reduce this risk. Check between the top and bottom decks of the pallets while elevated on the forklift to look for droppings at a minimum.

6. Negative Building Pressure. One of the most expensive structural deficiencies to correct is a negative pressure situation, yet it can be responsible for bringing a wide variety of insects into a structure. In worst case scenarios, negative building pressure can make it almost impossible to open a door because the force of the outdoor air pressing toward the door is so strong. Negative pressure can pull insects into a building whether they want to come inside or not. Insect attractive lighting, building temperatures and food odors emanating from the structure can add to the complexity of the issue.

7. Improperly Functioning Air Doors/Curtains. Air curtains can provide a false sense of security when it comes to preventing pest entry, especially if the right air door is not selected and maintained. Over time, the doors may not function as well as originally installed, or may not have been installed correctly in the first place. An improperly functioning or poorly installed air curtain can do more damage than no air curtain by pulling insects into the building. The proper air stream should be 2-5 inches wide at the nozzle with a minimum air velocity of 1,600 fpm (feet per minute) of air, 3 feet above the floor and across the entire span of the door opening. Food facilities should periodically check their air doors for proper functionality. If a building has a negative air pressure issue, it may be difficult to find an air door or curtain strong enough to compensate for the force from the outdoor air. Negative air flow must be considered in selecting the right air curtain.

8. Dock Plates. Because of their nature, gaps around the dock plate may be required to permit movement. The best dock systems consist of a plate which is lowered from an upright position into a trailer versus the dock plates which are incorporated into the floor. Dock plates that are incorporated into the floor will have spaces around the plate that need to be sealed with brushes or plates. Special care is needed to ensure a proper seal where the dock plate seal meets the door seal. In addition, there will be chain pull openings, which require sealing. There are several different door seals available, including seals for the chain pull area, to exclude pests. Xcluder is one product line offering dock plate seals, door seals and dock plate chain pull seals.

9. The Wrong Screens Used For Doors, Vents And Windows. Most insects will be excluded using normal sized window screens. The average mesh is designed to exclude pests like house flies and mosquitoes. However, some insects, like fungus gnats and thrips, will get through normal window screening and require a smaller mesh screen. In the search for zero insect activity, these smaller mesh screens may be necessary, depending on the type of exterior pest pressures. PMPs should consider working with customers on this additional level of exclusion. BioQuip and U.S. Netting are two suppliers of finer mesh netting for small insect exclusion. In addition to the right size mesh, all screens should be tight-fitting and repaired if tears occur.

10. Floor Drains. A sewer system can provide an ideal harborage for pests like small flies, cockroaches and rats, which then travel into facilities. Drains, which are seldom used for water management, can be particularly problematic. Maintaining drains through cleaning and proper grating is essential in helping keep pests from migrating into structures through sewer highways. If a drain is not needed for waste water management, consider having the customer cap it. If it is needed and supporting pest entry, consider using special caps or screened “socks,” which will allow liquids to flow down the drain but help keep pests out. Some of these exclusionary devices are designed for insects only and not rodents. Liquid Breaker Green Drain is an example of a one-way valve insert for insect exclusion.

Pat Hottel, a member of the Copesan Technical Committee, has almost 40 years of experience in the pest management industry. She’s been with McCloud Services in South Elgin, Ill., since 1980 and serves as technical director. Hottel holds a bachelor’s degree in entomology, a master’s degree in educational technology, and is a B.C.E.

Copesan is an alliance of pest management companies with locations throughout North America. To learn more, visit