Pest Management in Food Processing Warehouses

Once the infestation is found, it’s essential to remove it. In a warehouse, this is typically a forgotten ingredient. Removing and disposing the container and its contents will remove not only the food that the insects are consuming, but also the bulk of the infestation itself. Inspection and monitoring must continue to determine where the infestation has spread. Sometimes it has spread to a point where we cannot remove all sources. Fumigation, heat, or freezing may be solutions in these situations, but even these strategies are typically temporary. Sanitation must be present to prevent reinfestation.

Commensal Rodents

Commensal rodents are the rodents that actively attempt to get into and live in our facilities. They include the house mouse, Norway rat, and roof rat. These rodents typically enter a warehouse through unsealed parts of the building or in a pallet. Warehouses with docks are particularly susceptible to rodent entry, because completely sealing dock doors, plates, and levels can be difficult and costly. Even the most perfectly sealed facility can be vulnerable to rodents as a result of poor employee practices, such as leaving man doors propped open and not fully closing dock doors. Rodents are drawn to the shelter or food these facilities may provide and, once inside, immediately look for areas to hide. Balers, unused equipment, and other dark spaces make great homes for rodents. If not discovered quickly through inspection and monitoring traps, they can move, spreading throughout the facility.

Rodents, particularly mice, are also often brought into a facility in infested pallets. They are called “pallet mice,” and they make their homes deep within a pallet of ingredients. They usually enter from the underside and may not be visible from the outside of the pallet. When these pallets come into the facility and are placed for use, the mice begin to leave the pallet and spread throughout the facility. This can be particularly frustrating for a facility with excellent sealing and employee practices, who are unknowingly letting in a Trojan horse containing mice.

Monitoring and control: Multi-catch traps are the standard monitoring tool for rodents inside a facility. Sometimes, it may make sense to place them on the exterior of a facility if the PMP needs to know how big a population is or if they cannot risk a poisoned mouse dying inside the facility. Otherwise, it’s common to trust exterior rodent stations to inform whether or not the exterior population is present and active. This is judged by the amount of bait or monitoring blocks that are digested, droppings left behind, or gnaw marks on the station.

The key to control, particularly for pallet mice, is inspection at receiving. Employees trained to look for evidence of rodent activity may be able to identify infestations and reject infested pallets before they enter the facility.

When there is evidence inside the facility, whether that is droppings, live or dead rodents, nesting evidence, or other damage, PMPs can start to develop a control strategy. Snap traps with attractive lures are an excellent choice for quick control. The success of a snap trap program in a warehouse will be dependent on placement, lures used, and competing foods. A good snap program requires equal parts patience and creativity; placing the same traps in the same place with the same lure will rarely get your population under control. An aggressive snap trap program may need to be supplemented with rodenticides, where safe and legal, to apply and exclusion.

Flies

Flies that impact a warehouse are typically divided into two broad categories: small flies and large (or filth) flies. Though similar in so many ways, there is an important difference between the two. Small flies typically come from the interior, while large flies usually come in from the exterior. We may find both inside a facility, but when we are looking for the source, it will vary based on which fly is present. Small flies are a group that includes many species, and each has its preferred habitat and needs. Identifying the fly in the warehouse is an essential first step, because it will dictate whether the PMP should look primarily inside or outside for the source. This may also lead us to a particular food source. Identification, therefore, really gears the PMP’s inspection in the right direction.