Defense Mechanisms

They scurry around, sneaking under doors and through cracks. They jump, gnaw and eat throughout the day. They bother your customers and maybe even frighten them. They’re not Mighty or Mickey…they’re just regular old rodents. More specifically, they are house mice and Norway rats. And many PCOs have to deal with them daily. “Rodents are certainly in the top five” pests PCOs treat for, says Dr. Bobby Corrigan, rodent control specialist, Richmond, Ind.

Controlling rodents doesn’t require the use of a lot of pesticides. In fact, controlling them doesn’t take a lot of baiting, either. But controlling rodents does require a lot of organization.

“Rodents are all around us,” says Corrigan. “Rodents really are wildlife like rabbits and tree squirrels. Rodents are naturally occurring in woods, fields, streams and lakes. Ideally, the best thing for rodents is to be organized.”

And as homes and businesses expand further into the reaches of the wilderness and undeveloped areas, rodent harborages are being disrupted. People are taking over areas traditionally held by rodents, forcing the rodents to seek out other areas to inhabit.

“With people building into wild areas, they’re getting rodents,” says Michael Chapman, Western Exterminating, Irvine, Calif. “As populations fluctuate, the mice will come in and look for shelter.” Also, with El Niño’s rash of rain and heat, more rodent infestation problems have surfaced. Many weeds have grown, and as these grasses die, Chapman says, the rodents are more likely to enter peoples’ homes.

Corrigan agrees. “Pest populations rise to meet resources. If there are lots of resources available, the population can explode,” he says.

Weed control and vegetation management must occur, together with inside treatment, Corrigan says. To prevent rodent infestations, PCOs must analyze possible source points (inside or outside); keep rodents out of buildings by pest-proofing; and monitor for their presence. The most successful rodent control programs begin with thorough inspections and should always be conducted before any control work is started. A good inspection reveals the extent of infestation, harborages, entry points, and the safest, most appropriate and cost-effective control program for the specific situation.

WHO’S WHO. The two most common pest rodents are the Norway rat and the house mouse. The Norway rat is the most important urban rat pest for most parts of the world and is found in every state. The house mouse is the No. 1 rodent pest in most parts of the world. House mice live within cities and towns, as well as away from buildings as field rodents.

Weeds and vegetation are the natural habitat of the commensal rodent, Corrigan says. Weeds are a natural habitat, while weed seeds and insects serve as a food source. Protein is very important for rodent reproduction, which they get from insects. Carbohydrates are provided from the seeds. Weeds outside of buildings provide cover from hawks, owls, snakes, cats, dogs and other predators. They also serve as sources of water and nesting materials.

In putting together a rodent control program, try to keep bushes away from around the house, recommends Paul Hardy, technical director for Orkin Pest Control in Atlanta. “Don’t use ground-hugging plants,” he says. PCOs should also inspect and monitor burrows. They need to take a step back from buildings and look for other possible rodent harborages, Hardy points out.

Experts agree that the best way to control rodents is from the outside of structures. “(We try) to reduce the rodent population that’s moving toward the building,” Hardy says. “The real trick is to keep the rodents out of the building.”

Rodent-proofing and an ongoing environmental sanitation program are the best two practices for providing long-term and cost-effective control in a rodent IPM program. Although rodent-proofing is perhaps the best way to eliminate a rodent infestation for your customer, many times both property owners and PCOs alike don’t try this preventive measure.

INSIDE AND OUT. Hardy says when treating rodent infestations, Orkin professionals use bait stations in three ways: around fence lines and secured with an anticoagulant bait; around the perimeter of the building, locked and secured; and inside the building, in selected areas, for example in shipping, storage and public areas. Orkin technicians put glueboards in the bait stations and then monitor for rodent activity. Hardy says he prefers to use more IPM techniques than pesticides for controlling rodent infestations.

“There is no advantage in poisoning rodents,” he says. “Putting out baits first is not what we do. In fact, it is probably the last.”

Chapman says with its many commercial accounts, Western also aims to create a “triple perimeter” — at the fence, along the exterior of the building, and inside with glueboards and snap traps. And with residential accounts, he says, baits are rarely used baits, because of liability — the houses may be too close together and in neighborhoods, people are frequently out in their yards. “I don’t think (baits are) always necessary in those situations,” he says.

Being organized is a big part of rodent control, Corrigan says. “The best way to prevent rodent infestations is to be organized so you can easily spot their evidence,” he says. “They may be there, but you can’t see them.” He says PCOs need to pest-proof buildings by closing gaps, including under doors, to ¼-inch for mice and ½-inch to exclude rats.

Depending on the availability of food, such as garbage, rodents may move to a location where it’s easier to survive. “Sometimes rodents are close to buildings and they move in because of the cold,” Corrigan says. “Not that they have to, but it is much easier to move in.” Corrigan also says rodents may move into a garage where food is available, such as bird seed and dog food. Chapman agrees, saying that dog food in certain locations may lead to higher rodent populations.

But in addition to using pest control techniques inside the building, an even more important issue may be to prevent the rodents from being able to get inside in the first place. “I see this as a big weakness of our industry,” says Corrigan. “We do a lot of great work on the inside but overlook the outside.”

Hardy says that if PCOs do away with the food and water sources, they will frequently eliminate the rodent problem. “Get rid of standing water, monitor outside trails and droppings and stop up all holes,” he says.

One of the most important aspects of rodent control is how the PCO or technician goes about his or her treatment. “Once inside, it is important for the service technician and PCO on the job to understand there is no magic wand,” he says. “We allow rodent populations to expand because of how we live. PCOs need to analyze the situation.”

Hardy agrees that technicians play a crucial role in the process. “The key to rodent control is the technicians. The technician has to deliberately think ‘If I were a rat, where would I be?’ They have to think like a rat,” Hardy says.

Chapman says Western discusses rodent control and biology in the technicians’ initial training program. The company also uses two videotapes, one addressing how to anchor traps securely, and another about rodent-proofing techniques.

While it is important for technicians to be well-trained, PCOs need to realize the program to eliminate rodents has many aspects. PCOs should use a methodical approach when controlling rodents — you can’t assume anything, Hardy says. So what is the best way to eliminate a rodent infestation? Three words, Hardy says. “Monitor, monitor, monitor.”

Sidebar: Roof Rats Live The High Life

In several coastal and tropical U.S. cities (for example, San Diego, Houston and Honolulu, the roof rat (or black rat) is the most numerous and most significant rat pest species. Controlling this rodent is different than controlling others because of how its living habits differ from those of other rodents.

“Professionals have to think differently with roof rats. They have to look up in deep, dark crevices because that is where they are,” says Bobby Corrigan. “They are different than Norway rats — they’re much more secretive.”

Roof rats are a tropical species in the United States — they originated from Southeast Asian jungles. Since they are arboreal and lived in treetops, they adapted and acclimated to cities by moving higher up to the roofs of buildings.

Because roof rats prefer the elevated areas of treetops and roofs, they are by nature more elusive and less dependent on the food and harborage resources of humans. The dense growth of trees, shrubs and vines, woodpiles, sheds and accumulated yard rubbish all contribute to infestation of this rat.

“Buildings are trees to them,” Corrigan says. “They travel on telephone lines and trees. Those are the natural lines to travel.”

Michael Chapman, Western Exterminating, Irvine, Calif., agrees. “In California we deal with roof rats, and they are better climbers,” he says. “They like vegetation and vegetables, which we have a lot of.”

Any vegetation that climbs and provides dense cover is habitat for roof rats, Corrigan notes. So it becomes important to make sure vines, clinging ivy and the fronds of palm trees that are touching roofs are removed.

Sidebar: Top Ten Rodent Signs

1. Feces (droppings)

2. Gnawing damage

3. Burrows

4. Runways

5. Tracks

6. Grease marks

7. Urine stains

8. Visual sightings of live or dead rodents

9. Rodent sounds

10. Rodent odors (especially for mice)

Source: Mallis Handbook of Pest Control