To successfully exclude rodents in commercial food facilities, you need intel. Rodent expert Dan Collins shares tips for improving your intelligence gathering.

Rodents are the most common and successful mammals on the planet. They are highly adept at hiding, reproducing and using olfactory cues to navigate complete darkness.

“Their will to survive and ability to breed and adapt in facilities is unbelievable,” says Dan Collins, who has studied rodent behaviour for 30 years. Collins currently works as a consultant, and his previous experience includes serving as the director of pest management at Rose Acre Farms, a leading egg producer in Seymour, Ind. Before that, he owned Collins Pest Management and served as technical director of Action Pest Control.

Collins shared tips for rodent inspection, monitoring and exclusion in commercial food facilities at a PCT virtual conference in 2021.

STICK TO AN INSPECTION PROCESS. Collins adheres to a five-step inspection process when inspecting for rodents. “I cannot do pest control without it,” he says. This includes identifying the pest; looking for the source, extent and severity of the problem; identifying conditions that support the current or a potential infestation; determining best practices to eliminate the pest; and follow up.

His systematic approach to rodent management assesses the risk. He has a list of about 50 questions that when answered during the facility’s initial inspection helps “laser focus our efforts” on managing rodent-vulnerable areas. For instance, the list asks where the compactor is located, where entry doors are situated, where high-traffic patterns exist and whether the facility has a “boneyard” or outdoor space where equipment is stored.

When you consistently follow it, the inspection process becomes ingrained, and you’re less likely to miss key details compared to doing a haphazard assessment. “You have to be able to repeat what you do over and over, or you don't get good at it,” says Collins.

USE THE RIGHT INSPECTION TOOLS. To conduct an accurate inspection for rodents, you need the proper tools. For Collins, these include a flashlight, screwdriver, vice grips, tack puller screwdriver, offset screwdriver, mirrors and long and wide metal spatulas or scrapers. You need tools that will help you open holes and drains; the tack puller screwdriver helps reset tiles in drop ceilings, where rodents are active, he says. 

Another key item is a scientific ruler for measuring openings. Technicians often wrongly assume that if you can slide a pencil under a door, the gap is large enough for a mouse to enter. But mice typically can squeeze through a 6-millimeter gap, and “many pencils are wider than 6 millimeters,” points out Collins. As such, always measure gaps.

He also uses the ruler to measure incisor teeth marks on bait blocks to help identify the rodent. “If the incisor marks are two millimeters, I know I’m dealing with mice. If it’s four millimeters wide, I'm dealing with rats,” he says. 

EMPLOY MONITORING DEVICES. Monitoring helps you determine when and where rodents are active, the size of the population and whether they’re visiting traps.

Rodents typically become active about an hour after lights-out or people leave the facility. “You have to understand when those animals are active to best manage them, even if you're doing exclusion,” because “you have to do other things besides exclusion to knock them out,” Collins says.

Game cameras are “an awesome tool” for monitoring rodents remotely, he says. They help you track the animals’ travel patterns and behaviors, and sometimes where they’re getting in. A game camera in a drop ceiling helped Collins find where mice were slipping through a hole in the wall to get into the cafeteria’s dish carousel below. “Had I not had that camera up there, I probably would have never found this small entry point,” he says.

This insight also pushed the customer to make changes. Previously, dirty dishes were left sitting on the conveyor line overnight, which provided food for the mice. “We stopped that practice, obviously,” recalls Collins.

Electronic rodent monitoring devices or ERMDs let you monitor hard-to-reach areas, such as locked control rooms, attics or the tops of equipment without needing to move and scale ladders at every service visit. They help you monitor sensitive and high-risk areas around the clock and provide proof of surveillance to third-party auditors. ERMDs track when and where rodent activity is occurring so you can hone your control strategy, and they alert wildlife technicians to trap activity, prompting onsite service visits.

The devices also can help eliminate the “insanity” of continuous trap checking, says Collins. He had an account with 275 rodent traps that were checked once a week. Over a period of four years, his technicians checked 57,200 traps, finding one rodent. ERMDs may provide a less labor-intensive solution to scenarios like this.

Collin has some concerns about ERMDs providing false negative and false positive readings. He’s also worried companies may cut prices for rodent management at food facilities because less labor is required. As well, companies may use the devices as a marketing gimmick versus taking an integrated pest management approach, relying on ERMDs to do the job instead of properly training employees in rodent control.

ERMDs “will never replace a well-trained pest management professional with experience,” says Collins. 

PLACE TRAPS, THEN BAIT THEM. Except in facilities with severe rodent infestations, Collins will bait traps initially without setting them. This lets rodents get comfortable with the traps. A game camera helps him gauge the critters’ willingness to take the bait. Once rodents are visiting the trap regularly, Collins sets it.

It’s important to explain to customers why you are taking this approach, he says.

Without pre-baiting traps, you might catch 90 percent of the rodent population, but “we need to get to 96 percent reduction to crash the population. To do that, we need to habituate these animals to those traps, because if you don't, the likelihood of getting to 96 percent control is very low,” he says. Then, the rodent population rebounds, the customer is unhappy, and you get called back.  

EMBRACE RODENT EXCLUSION. “Exclusion is without a doubt one of the most important tools we use,” says Collins. Every pest management company doing rodent control should be providing exclusion services, he says.

It is, however, a “millimeter by millimeter” job, says Collins. That’s because rodents don’t need a large gap to get into a food facility. “If their head will fit through it, their body will follow,” he explains. A house mouse can penetrate a quarter-inch or 6 millimeter crevice opening; a rat only needs a half-inch or 12 mm.

Such gaps often are found where there are door thresholds, pipe and utility penetrations (both interior and exterior) and holes or crevices in walls and floors.

An overhead door is “the most rodent-vulnerable door in the entire facility,” says Collins, who urged PMPs to closely inspect the corners of the door compression seal that meets the ground. Mice often chew through that rubber gasket and gain entrance to the facility, he points out.

Gaps under personnel doors pose similar challenges. Collins has even found mice living inside a hollow door. They got inside by chewing a hole in the bottom, floor-facing edge of the door.

Thoroughly inspect the “dark, shadowy corners” under equipment to find entry points, adds Collins. This will require getting down on your hands and knees.

While exclusion is highly effective at preventing rodent intrusions, it can cause rodents to pop up somewhere else. “Once you seal them out, it doesn't mean you've got them 100 percent sealed out,” so look for other areas where they may emerge until you’ve eliminated the population, he says. 

USE THE RIGHT TOOLS FOR EXCLUSION. A self-professed “tool jockey,” Collins recommends several tools for exclusion work. Topping the list: commercial-grade manual and battery-operated bulk caulk guns that hold 16- to 32-ounce cartridges or “sausages” of sealant. These can be bought at concrete supply stores, not big box stores.

Other important tools are tin snips that cut left, right and straight so you can smoothly cut metal in hard-to-reach corners; angle grinders and cutting heads with dust collection systems; hammer, cordless and corded drills; mixing tools for mixing bulk sealants; and hand tools like hammers, pliers, putty knives and wrenches. A wide range of fasteners also is key; fender washers are “critical,” he says.

Collins advised outfitting separate toolboxes for different kinds of exclusion jobs, such as concrete sealing and door sweep installation. Then, equip each service vehicle with the boxes so technicians have all the tools they need to do this work efficiently.

Employees must be trained on how to use these tools, some of which require respiratory protection, reminds Collins.

APPLY THE APPROPRIATE MATERIALS. Rodents are tenacious and have strong incisors. They can chew holes through hardware cloth that isn’t strong enough. They can chew through expanding foam “like a knife through butter,” and even chew holes in hollow block walls, says Collins. As well, they can pull up the edges of metal, hardware cloth and metal fiber material that isn’t secured and sealed down.

He advises against using expanding foam in food facilities and only installing door sweeps and compression seals that contain a rodent-proof metal-polyester fiber mesh. This material also can be installed in floor and wall crevices, in holes and around pipe and wire penetrations. Just don’t cut the material in a food facility, as the resulting metal shavings pose a food safety risk.

Use a commercial-grade elastomeric polyurethane sealant to cover the metal-poly mesh (except when used to fill weep holes) so rodents can’t push or pull it out. Self-leveling sealant is for horizontal surfaces; a more rigid sealant is best for vertical services. Hydraulic cement and sheet metal are other options for sealing up wall holes. Sheet metal, however, must be sealed around the edges to prevent the intrusion of stored food product pests into the facility.

Hardware cloth is a metal wire screen used to secure openings. The best is woven and galvanized. For mice, use 24-gauge wire; for rats, use 19-gauge, which is thicker. Install hardware cloth with screws and fender washers, not staples, which rats can pull out.

Collins spoke at the PCT Pest Control in Food Processing & Commercial Facilities virtual conference, which was sponsored by Bell Laboratories, Woodstream and Corteva AgriScience, which makes the ActiveSense electronic rodent monitoring system.