Nobody wants bugs, rodents and other pests in their plants. But somehow they get in. Finding out the how in that “somehow” is a good first step toward keeping them out.
A big building like a food or beverage plant will inevitably have gaps, breaches, channels and other pathways of ingress – some intentional and necessary, some not – that can admit pests. And they don’t need much room. Even rats and mice can get through any space their skulls fit through – and that’s only 12mm and 6mm, respectively. In fact, they prefer tight spaces that provide good cover from predators.
No plant can be hermetically sealed. But awareness of where pest entry is liable to occur and of signs that it’s happening are key elements of an effective pest-control program.
Dock door seals can be an entry point for pests if they have gaps. Photo: Orkin
The first step is to realize that pests often gain access in ways that plant personnel rarely think of. As Chelle Hartzer, an entomologist and director of technical services for Orkin, puts it: “It’s always those non-obvious ones that can create problems!”
Hartzer sees roofs as a big potential problem, especially since many of them are not inspected as often as they should be. Roofs often have air handling systems, which can suck insects inside, and vents, which may not be screened properly. She also mentions dock plates: “Dock doors are often sealed pretty well, but the seals around the bottom plates are sometimes overlooked.”
Patricia Hottel, technical director at McCloud Services, says floor drains are her No. 1 overlooked source of entry, especially for cockroaches and drain flies. She says proper drain design can prevent pest problems.
“Maintaining drain integrity can help reduce the potential for activity,” Hottel says. “Proper drain design is also important where drains are accessible for cleaning and maintenance. Grates should be removable and baskets should be used to help capture solids and facilitate cleaning.”
She’s also not a fan of channel drains, saying they’re hard to clean and maintain, and should be avoided whenever possible. Also, one-way drain valves allow water to flow downward but block access to pests.
Building blocks
A building’s overall condition is key to its security against pests; the better shape it’s in, the less likely it is to have breaches where pests could enter.
“Older construction may be deteriorating in places, have older equipment that may have been retrofitted-in (fitting square pegs in round holes), and just wear and tear on the building,” Hertzer says. “That being said, I have seen older structures that are amazingly well taken care of with hardly a single gap that pests could take advantage of, and nearly brand-new sites that have more openings than a cheese grater!”
There are certain architectural styles and construction materials that are especially conducive to pest problems. “Corrugated metal buildings are one of the hardest structures to seal and maintain sealed,” Hottel says. “The corrugations create numerous locations where pests may enter.”
Pallets are one of the many vehicles available to “hitchhiking” pests. Photo: Rentokil
Flat roofs are liable to collect water, which can help breed bugs. They are, however, the norm for most industrial buildings. Macy Ruiz, a technical services manager at Rentokil, says roof problems can be mitigated in several ways, including: avoiding rubber roof membranes or coverings because moisture can collect under them, creating a haven for pests such as ants, plaster beetles, and springtails; avoiding rock coverings, which can attract birds and other pests; and cleaning gutters regularly.
Jerry Heath, product manager and staff entomologist for Industrial Fumigant Co. (IFC), mentions other potentially problematic construction materials.
“A lot of pre-fabricated materials are used in industrial construction – sheet metal-clad insulated panels for one – that provide wonderful harborage for insects and rodents as well as travel pathways to all elevations of a structure,” Heath says. “Hollow block walls are also notorious harborages. Both of these need penetrations for pest entry (but that happens soon enough), or uncapped tops/bottoms. False ceiling voids are another notorious harborage for many kinds of pests.”
Calling cards
When pests establish a way into a plant, they often leave evidence of their entry. For example, rats and mice leave sebum trails that show up as grease stains on materials like concrete. (These serve as markers that help the rodents find their way back into a building.)
“Rodents are notorious for their travel pattern indicators,” says Dominique Sauvage, senior director of field operations, training and quality at Copesan. “Rodents have an oily coat, which means they will leave rub marks (sebum) if the area is used often. These rub marks can be very subtle in some cases and can be an early indicator of a problem. Rub marks can also play a role in determining where the rodent is navigating as the marks will indicate a path well-travelled."
Rodents also enlarge small openings by chewing, which leaves teeth marks and sometimes telltale particles of wall material.
“Rodents are chewing machines,” Ruiz says. “They will gnaw at small holes to make them bigger and allow them to squeeze inside. They may also chew wiring. Gnawed product or packaging on a pallet may indicate a rodent has been at work on that pallet or in that area.”
Traps, an integral part of most pest control programs, can furnish clues as to where pests are getting in, Hottel says.
“Some of the rodenticide baits are specially colored and will fluoresce in the droppings of the rodents that have fed on it,” she says. “If we are using one of these colored baits on the exterior and see colored droppings on the interior, it is a good indication that the rodents moved in from the exterior. We can also use traps or monitors to help determine patterns of activity and link the captures to probable entry points.”
Hertzer suggests a decidedly lower-tech indicator: blocking a suspected entry point with a crumpled piece of paper. “If the paper gets pushed out or moved, you know that is an active spot and to focus on that first, then get to those areas that aren’t active … yet,” she says.
Hitching a ride
Finding breaches in buildings is not the only way pests get in. They often come in as stowaways.
“Absolutely, there are tremendous opportunities for pests to enter as infested commodity ingredients, in shipments of all kinds, and as hitchhikers,” Heath says. “Every kind of shipment should be subject to some level of inspection or sampling. Sometimes it is routine for certain commodities to be fumigated prior to shipment or fumigated in transit by rail -- flour for example.”
Food and beverage plants constantly admit all kinds of materials and equipment, any of which can harbor pests: incoming ingredients, trucks and other vehicles, pallets, forklifts, even new equipment.
“It is extremely common for pests to make their way into a facility by infesting incoming product or hitching a ride on pallets, in equipment, or in machinery that is used to move product around a facility,” Ruiz says.
Guarding against “hitchhiking” pests can be tricky, in part because the risk depends in large part on how responsible a plant’s suppliers are.
“If they have a great pest management program in place, it’s not too likely that they will be shipping in pests,” Hartzer says. “If you have a supplier that may not be as invested in their program, it’s more likely something could come on one of those shipments.”
Ways to prevent “delivered” pests include: carefully inspecting all incoming products, for things like small holes in product packaging, webbing, casings, droppings and live or dead insect and rodent pests; not leaving supplies sitting outside or on open loading docks; having new equipment cleaned and serviced before installation; and using plastic pallets when feasible.
Alex Blahnik, field training manager for Wil-Kil Pest Control, says pest arrival is a good reason not to have excessive supplies of ingredients on hand. “Any food facility that is serious about preventing pest infestations will inspect all inbound food products, practice the FIFO (first-in, first-out) concept and not order more product than can be used in a reasonable amount of time,” he says.
Heath cautions that employees can also unwittingly transport pests. Roaches sometimes enter lunchboxes, and bedbugs can hide in clothes (although he notes that most food plants aren’t favorable environments for bedbugs).
Plugging the gap
Once it’s known how pests are getting in, the task then becomes keeping them out: repairing the breach, hole or gap so that pests can no longer get in. The methods and materials used in such repairs vary by case, but Ruiz identifies some general principles that should be adhered to.
“The first principle in exclusion is to make sure there is no existing pest issue that can create problems,” she says. “Sealing an opening in a wall before confirming that the activity has been removed could cause a secondary pest issue. For example, if you seal a rodent into a wall and it dies there, its decomposing body may attract other pests.”
Choosing the proper material is crucial. Hottel cautions against relying solely on expanding foam, which she calls “one of the most overused and ineffective sealing materials.” Ruiz says that, depending on the details of a repair, pest-proof materials might include 18-mesh screening or smaller, concrete, silicone-based caulks, metal flashing or hardware cloth.
Pest experts say fixing breaches is a lot like running a pest-control program in general: Take the initiative, get it done and stick with it.
“Acknowledge the problem,” Heath says. “Don’t ignore it or sweep it under a rug. Maybe it’s an easy fix, or maybe it’s a capital expense. Keep the issue open as a deficiency and be honest about communicating what is feasible to be done in the short term to mitigate, and/or prospects for a long-term solution.”
