[Rodent Control] Bolstering the "4 Lines"

For reasons of both food safety and regulatory compliance, pest management professionals must design and carry out rodent control programs that eliminate existing infestations and keep the premises rodent-free.

Adding to the complexity of our task is the need to comply with the inspection standards of a variety of non-governmental inspection agencies, not all of which (yet) adhere to exactly the same definition of what constitutes adequate pest management practices — and not all of which agree on which practices are permissible.

How can pest management professionals who wish to serve the food-processing and storage industries navigate the narrow strait between regulatory requirements and the need for perfect rodent management results on one side, and third-party inspection standards on the other? Beyond the placement and maintenance of those little silver and black boxes, how does one accomplish effective rodent control in food plants? The purpose of this article will be to:

• Describe those considerations that must be taken into account when designing a rodent control program for a food-processing plant or warehouse.

• Describe options for setting up and conducting preventive rodent control programs outside of and inside of food plants and warehouses.

• Describe what to do when, despite preventive measures, a rodent infestation becomes established in or around a food-processing plant or warehouse.

• Describe what an actual service visit should consist of, as this pertains to rodent prevention and control.

WHO IS OUR CLIENT? Our clients absolutely cannot afford rodent contamination and they must have effective rodent control and prevention. Not only are our clients obligated to comply with the provisions of the U.S. Food, Drug and Cosmetic Act, which states that any food produced or stored under conditions whereby it may become contaminated is deemed unfit for human use; they also live and die by their third-party inspection scores, and must have compliance with inspection agencies’ standards. They must protect their brands at all costs, and this is why they pay outside inspection agencies to be tough in their judgment of their facilities’ food safety picture.

If we as pest management professionals understand these facts and act accordingly, our clients will reward us with their continuing loyalty.

KNOW THE DEFENSE LINES. The three lines of defense? No, four! Dr. Bobby Corrigan has made the point that, though our industry now accepts that there are three lines of defense in a well-designed rodent management program (fenceline, exterior and interior), there really is an additional line of defense that comes before the other three. That is, the careful analysis of each facility’s unique structural condition, the rodent pressure on the facility, and the inspection standards to which it must conform.

The first step in preventing and controlling rodents in a food-processing or storage facility — the "first line of defense" — is careful situation analysis. We need to know what amount of defense is needed. After all, too much time spent checking unneeded rodent devices means time taken away from other service elements — like thorough inspections. Too little rodent equipment means some rodents might find their way into the building and survive long enough to do damage.

Assess the rodent pressure on the facility. Are mice abundant around the plant? Do conditions exist immediately outside and in the close surroundings that are conducive to rodent infestation? Are there burrows beneath the building, or in the ground nearby? Conditions conducive to rodents mean that more rodent pressure is on the facility, and more equipment is going to be needed. More doors will need to be protected, and spacing of devices will need to be closer. Depending on how serious the rodent pressure on a facility is deemed to be, exterior rodent control devices (bait stations, traps, or some combination of both) might be spaced closer than 50 feet apart, or as much as 100 feet.

Here are some conditions that might be considered conducive to migration of rodents toward a plant, thereby increasing rodent pressure:

• Cluttered storage of old equipment ("boneyards").

• Weeds growing against the building, or among stored equipment in a "boneyard," or along nearby railroad tracks.

• Food odors or warm air currents emanating from the building, especially if the building is old and not very tightly constructed.

• Infested premises nearby.

Assess the structure itself. Is it a newer building with tight door seals, or an old building with holes and gaps and multiple additions and renovations? Newer buildings typically mean fewer opportunities for rodents to enter. Older buildings will often have a higher rodent pressure index by virtue of their less-tight construction.

Also part of the situation analysis is to answer this question: What inspection agencies will be involved in rating food safety in this facility (there may be more than one)? What do these agencies require in terms of equipment used, and in the spacing of the equipment? Good sense should always rule, but if the inspection agency responsible for assessing food safety in a particular facility has rigid "yardstick" standards for how rodent control devices are to be placed and how far apart they are to be spaced, these must be obeyed.

Finally, find out something about the rodent history of the facility. Are mice typically caught inside? How many mice are typically caught in a year? You’ll make a different decision about placements of rodent control equipment in and around a plant where only one mouse has been caught in two years than in a place where numerous mice are caught each month. Previous pest control log book records usually are available, and can provide the history that is needed in order to assess the frequency and likelihood of rodent invasion.

Continuing beyond the planning phase and into the day-to-day execution of the rodent control program in a food plant or warehouse, the pest management professional servicing a food-processing or storage facility must remain involved in situation analysis, and get to know his or her client’s operation as well as possible. The pest management professional must be able to answer such questions as:

• What is manufactured here?

• What raw ingredients and supplies are brought in?

• Where do raw ingredients and supplies come from, and how do they get here? (By truck? By rail?)

• What operations take place in each of the plant’s areas?

• How are the products manufactured or stored here distributed?

• How are goods organized and segregated — raw materials, finished product, product on hold, rejected/inedible product, waste?

By knowing what processes take place, the pest management professional can identify pest vulnerable areas to which he or she must pay particular attention within the plant. By knowing something about the origin, transport and acceptance of raw ingredients, the pest management professional can keep a wary eye out for hitchhiking rodents. Similarly, by taking interest in the distribution chain, the pest management professional can help his/her client prevent infestations from happening after products leave their dock. In short, a technician who has studied the process flow to some extent is better equipped to anticipate and prevent problems, and to more readily understand what is happening when an infestation does arise.

This line of defense is not always available for placement of equipment, but when it is, it’s useful. Rodents commonly travel along interfaces between "wild" and "tame" areas. The fence itself provides a vertical structural guideline along which rodents will travel, just like a wall. And just beyond the fence might be an area of unmowed grass or weeds, which provides cover and a continuous influx of new rodents. Therefore, fencelines can be excellent places to intercept mice and rats and reduce their populations before they have a chance to move close to a building.

Options from which to choose for fenceline devices include bait stations anchored to the fence; or enclosed trap placements. Either one will remove mice, and possibly rats, from the population pressure bearing on the facility itself.

It may be that a remote perimeter exists, though there is no fenceline. For example, a retaining wall, access drive or property border (the interface between wild vegetation and a groomed lawn), might present opportunities for intercepting incoming rodents. Safety must be a primary consideration, however. In the absence of a secure fence, think twice or three times about the use of rodenticides, even in anchored tamper-resistant bait stations. In less secure situations, enclosed trap stations might be of some value in reducing the number or rodents — especially mice — that are able to approach and threaten a food-processing facility.

Depending on the intensity of rodent populations adjacent to the facility being protected, bait stations or traps placed around the fenceline or remote perimeter might be as close together as 50 feet or even less; or they might be 100 feet apart. The frequency of this service is typically monthly or twice monthly.

This is our last chance to intercept and catch and/or treat for rodents before they get inside. There are at least four options for devices along the exterior perimeter of a building:

• Bait stations containing toxic bait. Use a block formulation, with the blocks secured inside of an anchored bait station. The bait stations must be anchored in some way — either by fastening them to a concrete patio block; by staking them into the ground; or by fastening them to the asphalt pavement or to the building itself.

• Bait stations containing non-toxic bait. This is an option if your client has made a corporate decision to reduce pesticide use. Ounce for ounce, rodenticides represent a big opportunity for reducing pesticide use. Non-toxic bait blocks can be installed in bait stations for monitoring purposes; a "hit" on one of the non-toxic bait placement triggers a temporary switch to toxic bait in that location only. When activity ceases, the toxic bait is again replaced with non-toxic monitoring bait.

• Bait stations containing multiple-catch or snap traps. One version of this option is the large metal "rat cafeteria" with a Ketch-All or Tin Cat inside. Another is a plastic exterior bait station with snap traps inside. Either way, this option offers the advantage of ensuring that the animal that interacts with your control device does not survive long enough to get inside the plant (Bobby Corrigan calls this a "dead mouse walking") and cause contamination before it expires. Exterior traps have been shown to work very well as a line of defense against rodent invasion. Exterior traps are especially attractive as an option for Organic programs, where non-chemical means of control must be considered before the use of pesticides is justified.

• Bait stations containing snap traps and toxic (or non-toxic monitoring) bait. This is an option if both rats and mice are a possibility, or to affect those mice that, for whatever reason, might not choose to interact with a trap.

Depending on rodent pressure and condition of the structure, as well as on requirements of the outside inspection agencies visiting the plant, exterior devices might be anywhere from 40 feet to 100 feet or even more apart. Service frequency is typically monthly or twice monthly, though at least one inspection agency specifies that exterior devices must be serviced weekly.

Here’s a riddle: When is a mouse trap not a mouse trap? Answer: When the mouse trap is placed next to a door or alongside a wall inside of a food-processing plant or food warehouse. Inside of the plant, a mouse trap — whether Ketch-All, Mouse Master, Corner Cat, or some other brand — is a monitoring device, not a mouse trap. A mouse caught inside is a signal that something has gone wrong with the outer levels of defense — the things that were supposed to prevent any mouse from getting inside. A mouse caught inside of the plant is a big deal, and catching a mouse indoors must trigger a sequence of events whose purpose is to ensure that the mouse’s entry route is found and plugged, and that any further mice that might have gotten in are eliminated.

Whichever type or brand of devices is used indoors, and however widely or closely they are spaced, it should be expected that a rodent capture inside of a food plant or warehouse will not be treated as a routine occurrence. The action equivalent of clanging alarm bells, wailing sirens and bright, probing searchlights should result from any mouse caught inside.

At the very least, a mouse caught inside should result in the following activities:

• Document the catch.

• Investigate to find out how the mouse got inside. Did it hitchhike on a pallet of product or ingredient? Did it crawl in through a gap beneath a door? A detailed inspection must be conducted in the area near the trap in which the mouse was caught.

• Communicate to management what they need to do in order to support your efforts to bring their facility back to pest-free status. This might be: making repairs to a door; establishing/enforcing a policy of keeping doors closed; restoring a forgotten 18-inch inspection aisle; or conducting careful inspections of trailers delivering ingredients into the plant prior to unloading the trailers.

• Close the loop. This means that management signs off on the work they completed. The pest management professional states in a log report that no further rodent activity can be detected, and that it is time to return to a monitoring status.

Additional actions that might be triggered by a mouse capture include addition of more equipment (additional multiple-catch traps, snap traps, or even secured non-toxic or toxic bait placements) on a temporary basis. When this is done, make sure to show the position of temporary additional equipment on the facility’s equipment diagram. Make sure all non-permanent devices are removed from the plant and deleted from the facility map after the crisis is resolved.

As in the case of exterior devices, spacing of devices inside should be decided upon while considering not only the "yardstick" standards with which we are all familiar. Much more important is the actual risk associated with any potential entry point. A facility with high mouse pressure on it might need mouse traps between each pair of dock doors; in buildings with low mouse pressure and a history of few or no mice caught, multiple dock doors might be protected by only one trap for every three or four dock doors.

Depending on rodent pressure, condition of the building, the inspection agency’s standards, and some other factors, devices might be spaced as closely as 25 feet or less, or as much as 50 feet apart. Service frequency for interior devices is almost always weekly. This is not just because of stated rules pertaining to service frequency; it is also because no inspection agency would tolerate a decomposing rodent inside of a trap, and weekly service is the bare minimum for ensuring that no decomposing mice are found in process areas.

Editor’s note: For guidance on individual inspection agencies’ requirements pertaining to device placement, spacing, and service frequency, visit www.pctonline.com.

The author is technical director at Plunkett’s Pest Control, Fridley, Minn. He can be reached at jbruesch@giemedia.com.