Randolph, Wisc. pest control specialist Kyle Stiemsma is describing a job he set up at a dairy last year. “The guys turned on their silo unloader,” he says, “and there were about twenty rats that jumped off the 60’ silo. About half of them survived, and took off running; every time they’d kick it on, there were rats running everywhere, and when they emptied out the silo, there were burrows all over the bottom of the silo.” The problem, says the owner of Terminator Pest Control, was lack of sanitation. “There was grass three feet tall and weeds everywhere.” To maintain co

ntrol he says, “Keep a 3’ wide band around buildings, where it’s clear of debris, grass and weeds; spray with Roundup and put down a barrier of stone – anything will be a huge help…you just have to keep on top of it if you’re doing it yourself or hiring somebody else to do it.”
 
Stiemsa’s family-owned company is among 6,000 members of the National Pest Management Association. Greg Baumann, the group’s vice president of technical services, says there are a number of good reasons to hire a professional pest control service, and among them are the many other things dairy farmers have to worry about. “This is not something that they want to spend a lot of time on,” he says. “In addition, an extra pair of eyes is very good because somebody from the outside could find some maintenance issues that might not be obvious to people that are looking at it every day. And these people are trained in pest management; it’s their area of expertise.”
 
And, he says, there are very good reasons for dairy producers to get control of any rodent infestations. For one, they can scare the animals, reducing productivity; and, they’ll literally eat up the profits by devouring the food. “They may not eat a lot,” says David Drake, University of Wisconsin Extension wildlife specialist. “But if you accumulate that amount that they’ve eaten over the course of a year, it might add up to a sizeable figure.” And in mixed feed, they’re also depriving the cattle of minerals and nutrients carefully selected to balance the herd’s diet.”
Drake lists a number of other threats posed by rodents. They’re disease carriers; they also are hosts to mites, ticks, fleas and other ectoparasites. Those unsavory traits, plus the fact that they bite, makes them threats to human health as well. And, he adds, “They’re rodents; they’re constantly gnawing on stuff, so they can chew through power lines.
 
They can do structural damage by chewing through rafters, boards, things like that as well.”
For those producers who are inclined to try to control their own rodent problem, Drake says the most effective method is to use a rodenticide; some are sold over the counter, while others require a pesticide applicator’s license. He recommends enclosed bait stations to avoid poisoning the cattle or other non-target animals. And if you use a blood-thinning agent like Warfarin, your work doesn’t end when you place the traps; you have to pick up the carcasses, or pets and wildlife could eat them and get secondary poisoning.
But whether you try your own hand at extermination or hire it done, there are measures you will need to take to keep the rodent population down. Drake doesn’t think it would be worth the time and money to completely eliminate rats and mice—many facilities are full of holes, and “It doesn’t take much more than ½” or so of a gap for some of these smaller mice species to get in,” he points out—but you can make it less appealing to them. He recommends limiting the available of food; don’t put feed out in open hoppers, for example, and clean up right away after feeding. Also, eliminate all open, standing water sources, like puddles or farm tanks; that will handle the big Norway rats that are problems throughout the country, although it may not affect the mice.
In addition, Drake says, “you’ve got to get rid of all the hiding places. If you think about raised hoppers that are on legs above the floor, all those areas that rodents like to hang out around; they’re up in the rafters. If you have ground silage bags, the rodents will be inside there; if you’ve got grain storage, it is near impossible to keep rodents out of those areas—you’re providing both shelter and food.”
Baumann chimes in, “Sometime the rodents are not going to have to go to the food; the food will come to them. With some of the operations today, you have conveyors and what have you, and people see, ‘OK, there’s a little seam that’s opened up, and you have some feed spilling on the floor. No big deal; I’ll eventually sweep it up.’ But if it stays overnight, for example, and rodents might be most active at night, you’re creating a food source then.”
Norway rats, says Baumann, are called “commensal” rodents. That means, in essence, they share the table with humans; in colder climates, they’ll seek out a warmer place to stay, even if it’s yours. NPMA preaches Integrated Pest Management (IPM), and Baumann says rodenticides by themselves will not solve the whole problem; IPM requires three steps: “First, you do a thorough inspection to find if there is evidence of infestation. You identify the problems—what kind of rodent it might be; what kind of maintenance needs to be done, is there a hole in the wall where these things are getting in, is there excessive feed spilling somewhere? And then the third step is control measures. It could be repair work; it could be just a difference in practices, and it might be the use of rodenticides, as well.”
When the situation is under control, the dairy owner needs to keep an eye on it to make sure it doesn’t blossom anew. That could mean bringing in a pest control specialist on a regular basis to look for new potential problems. 
Stiemsma says upon visiting the farm, his company will make a list of what the operator needs to do to cut back on harborage for rodents. Debris, and overgrown grass and weeds, provide the animals shelter and cover; they’ll start burrowing, and the population will grow. “Eliminate these junk piles here, try and clean this area in the cow yard that there’s a lot of burrowing around the foundation or around bunkers, anything like that where a lot of stuff accumulates and just doesn’t get cleaned out.”
Where he sees a lot of burrowing has taken place, he pours in tracking powders and baits; he’ll typically offer a monthly follow-up service but may have to revisit several times a month where needed. Stiemsma doesn’t lock his customers into contracts; sometimes they’ll want to take care of it themselves, after Terminator has knocked the rodent population down.
But he’s not sold on over-the-counter rodenticides. “It’ll work,” he says, “but it takes more of it to kill them, whereas the stuff that we use takes a very small amount, and it kills them quicker.” In addition, he says federal regulations are changing, and non-enclosed baits will no longer be accessible to non-professionals in the near future. And he says rats, in particular, are hard to control because they’re neophobic—that is, afraid of anything new, and that includes traps. Rather than consume the rodenticide, they’ll avoid it for a time.
And Stiemsma—whose father started the business in 1993 after his dairy barn burned down—doesn’t mind a little four-legged competition, either. “It’s all right to have a few cats around,” he says, “as long as you don’t overfeed them with cat food, they’ll be much more likely to go out hunting.” Hunting for mice, that is. When rats are the quarry, that’s when farmers give Stiensma a call.