Occasional Invaders: The Canary in the Coal Mine

Occasional invaders are pests, primarily insects, that live outdoors but will venture into structures in search of food, water, or shelter. Although they are not normally considered to be structural pests because they do not breed indoors, those that do get into the processing areas of a facility, or worse, into the product itself, will be considered a contaminant or adulterant. “Occasional invaders are considered to be nuisance pests for the most part,” said Clark Pest Control Food Safety Field Trainer and Content Developer Al St. Cyr. “But when they get indoors, they can quickly pass from nuisance to significant economic problem.”

Occasional invaders may include a variety of insects depending on the region in which your facility is located and the time of year. Some of the most common are centipedes, millipedes, ground beetles, crickets, spiders, and night-flying insects. In certain areas, boxelder bugs, stink bugs, and cluster flies also can become pests in the spring and fall. But no matter what the insect is, “these pests winding up in a facility demonstrate a lack of structural integrity,” St. Cyr said.

This lack of structural integrity means that other pests can get in as well. As such, said Western Pest Entomologist John Kane, “Occasional invaders can be kind of like the canary in a coal mine.” They are a warning signal that if they can get into your building, so, too, can higher-risk pests. “The presence of occasional invaders indicates permeability to pests,” he said.

Occasional invader entry also can be due to employee practices, Kane said. “When I see them, it implies that there is access somewhere within a reasonable distance. It may be a structural issue or a cultural issue—such as employees propping doors open.”

Thus, the best defense against occasional invaders is prevention. “What you need to do is develop a long-term strategy,” St. Cyr said.

Steps to consider for inclusion in such a strategy are:
 

1. Inspect the facility and property. Conduct a detailed, honest inspection of the facility and the property, using sticky traps to determine exactly the pests with which you may be dealing, St. Cyr said. Look at the history: “There is something that is attracting the pests. Find out what it is and remove it.” It also is important to look not only at the plant’s property, but also at any areas that are immediately adjacent that may be attracting the pests or providing conditions conducive to their survival. In some cases it may be necessary to take a situation into your own hands—such as the food processor did who was having issues with occasional invaders originating from the field of an adjacent airport. Because the airport would not mow the field, the processor eventually hired a lawn company to do so—which eliminated 90% of its problems.
 

2. Use glueboards at entrances. Using glueboards at doors can help reduce the migration of insects into the plant in the same way that flying insect traps can catch flies before they have a chance to move farther into the facility. One easy way to do this is to place glueboards in the rodent control stations that are set at these points and check them regularly for any insect captures.

Using glueboards by doors also can double as insect monitoring stations, Kane said, providing a warning signal that insects are gaining access and indicating a need to determine the cause.
 

3. Manage the exterior. “Bugs try to stay in their natural habitats,” said Guardian Pest Control Technical Director Hao Yu, so if you don’t create a “walkway” into a structure, pests are less likely to go there on their own. Such walkways could include mulch or other ground cover up against the building; instead, it is recommended that a six- to eight-inch non-vegetative buffer be maintained around the perimeter of the building. “If you can do a foot out, it’s even better,” Yu said.

The foliage around a building can also be attractants and enable pest survival, he said. “If you have boxelder trees outside, you will, for sure, have boxelder beetles.” Additionally, native plant species are better than exotic, as native species will support local insects, but will keep populations down because there is a natural balance. Exotic plants, however, can overly support a particular insect species, enable large populations to build, and increase the likelihood that this insect will make its way indoors.

This is an area where the pest management professional can be very helpful, St. Cyr said. They can examine what is planted and explain, for example, “Here’s what you can expect, and here’s how to prevent it or how you can change the plants to prevent it.” It is also in this respect where a PMP/plant partnership is particularly important. For example, he said, the pest management professional’s inspection may reveal that you need to take out plastic that was put beneath mulch or plants, and use natural rock or some other barrier instead.

Once attracted to and at the exterior of the building, the insects will find gaps and cracks to slip through and into the structure. Thus managing the exterior means conducting regular inspection and maintaining the structure and grounds, removing attractants, and sealing and repairing any gaps and cracks. While newer buildings are less likely to have insects invade through worn seals, loose siding, eaves, etc., inspections need to be regularly conducted to watch for the beginnings of any structural deterioration, etc.

Additionally, Kane said, “The way a building breathes is often overlooked.” That is, determining whether a structure, or area of the structure, has positive pressure (which will push insects out) or negative pressure (which will draw them in) enables corrective action, where and when needed.

4. Manage exterior lighting. “I frequently find exterior lighting is very important to occasional invader presence,” Yu said. The insects, such as night-flying insects, are attracted to the lights; then other pests, such as spiders, are attracted to the night-flying insects. To prevent this, LED, high-pressure sodium vapor, or halogen lights should be installed, which are less attractive to insects than incandescent and fluorescent lighting.

5. Manage the interior. While occasional invaders do not—usually—breed indoors, conducive conditions can enable them to survive longer and get farther into the building (and, even, sometimes breed indoors). For example, if ground beetles come in through loading dock door #7, where interior conditions are moist and dark, they will be able to survive longer and potentially move into processing areas.

Prevention is also important because elimination methods, such as fumigation, can kill the insects, but leave dead insects within the walls, which can cause secondary pest invasion, such as warehouse beetles, which feed on the dead insects.

6. Track pest records and seasonal impacts. “A good facility manager should evaluate pest management records on a regular basis,” Kane said. Track any trends, both seasonal and location within the structure, as this can point you in the direction of corrective action. When you do find a trend, follow the “5 Whys” of an iterative question asking:

a. Why is there a wasp on the glueboard? (It got in from outside.)

b. Why did it get in? (The door was open.)

c. Why was the door open? (It was propped with a wooden block.)

d. Why was it propped? (Employees wanted to get in and out easily.)

e. Why did employees want easy access? (They wanted to take a smoking break.)

The final answer explains the issue, its corrective action, and why an alternative solution (e.g., spraying for wasps) would not have worked. “It’s almost never a real mystery,” Kane said.
 

7. Educate employees. “From a pest control point of view, the fixes are usually simple,” Kane said. “The challenge is getting buy-in from management and employees.” For example, management may fix the issue by requiring that doors not be propped open, but if employees only comply in the presence of management, the issue will remain. The best way to get buy-in, Kane said, is to educate employees on the actual costs of occasional invader (or any pest) presence; explaining the tens of thousands of dollars that could be lost if a shipment is rejected for insect presence, a recall is required, or a food poisoning occurs. Then explaining, further, how this could lead to company cut backs, including worker job losses. “The consequences of failure to follow GMPs can be high,” he said. “Consequences are happening every day.” Thus, “compliance is safeguarding yourself and safeguarding your staff.”

8. Understand the pest. Beyond indicating an access issue, accurate identification and understanding of the type of pest found also can indicate further issues. For example, springtails can indicate a moisture issue; the predatory/scavenging nature of ground beetles can be indicative of dead insects in walls; fungus beetles can mean that roofing materials were contaminated during construction and need to be replaced; and what may initially be thought to be an Oriental cockroach could actually be a new invasive species of Turkestan cockroach. Pest species also can be a warning signal of needed corrective action.

By their very definition, occasional invaders only occasionally invade structures, and when they do, it is because there is something attracting them inside. Because of this, in most cases, the occasional invaders are a facility issue, with corrective action to be dealt with through structural or cultural improvements rather than pesticides. As St. Cyr said, “It’s not always easy, and it doesn’t always come out of a one-gallon spray can.”

The author is Editor of QA magazine. She can be reached at llupo@gie.net.