Taking the Bait

Annual Rodent Control Issue - Annual Rodent Control Issue

Chris Keefer, Ph.D., Syngenta technical service manager, shares five essential tips for baiting rodents.

August 5, 2021

© Sergey Bolkin | iStock

“Do your homework.” That’s the top advice Chris Keefer, Ph.D., a Syngenta technical service manager covering the southeastern United States, gives new technicians who are selecting a rodenticide and planning to bait at an account. PMPs must understand the pros and cons of different rodenticide active ingredients and formulations, but they must also have a solid grasp on rodent ecology and biology, Keefer said. To better understand baiting best practices, Keefer, who has worked in the industry since 1994, offered five of his top tips.

1. Don’t rule out baiting from the get-go.

“I really think PMPs should consider baiting for rodents at all accounts,” said Keefer, “and then after an extensive review of the variables of the account, make a final decision on whether baiting is appropriate or not.” Many variables can play into that decision, he said: Are children present at the account? What about domestic animals? Are there non-target animals that could come into contact with the bait? Keefer said people can be bait-shy when it comes to residential accounts. “But if you really assess the account and all these variables, you can come to an intelligent decision on whether or not baiting should be utilized at an account,” he said.

PMPs also should determine what type of rodent they are dealing with, Keefer said, and estimate the size of the target pest population. “That’ll tell you how much bait you may need in order to gain control,” he said. Then, determine the range of that target population. “Is it just a really small population in one room of the structure, or is it really spread out, and maybe it covers a vast area?” he asked. Then, PMPs can determine where they’ll have to apply baits to be successful.

2. Perform a proper inspection before baiting.

A proper inspection of the account will lead PMPs to the best spots in the account to bait, Keefer said. “You want to get the product as close to the target pest as possible without disturbing them,” he explained. In a proper inspection, Keefer said PMPs should be looking for signs of rodent activity. A major one is fecal pellets. Identifying those pellets allows PMPs to determine what kind of rodent is present in the account. “If you get into the literature, you can easily learn how to identify fecal pellets,” he said. Other signs to look for include gnawing damage, grease marks, burrows, runways, tracks in dust, urine stains and odors, Keefer said. Going straight to the source helps, too. “Interview the client or the folks that are there and ask them where they’re seeing rodents and where they’re hearing the sounds,” Keefer said.

Upon completion, a proper inspection should hint at the severity of the infestation and let PMPs know if the problem is localized in one area of the structure or more spread out. “By gathering this intelligence prior to implementing any of your control measures and any effort, you can maximize your effort and your time to gain superior control of the infestation,” Keefer said. Final steps should include examining rodent harborages and high-traffic areas to determine food and water sources. Finally, Keefer said, look at the least invasive control measure to non-target pests and the most efficient control strategies that can be implemented to gain control of the population.


3. Consider pre-baiting.

“Pre-baiting is essentially preconditioning the rodent to enter a bait station by placing small pieces of food or a food lure in that rodent station,” Keefer said. “So, this allows the rodent to enter the station and feed on whatever lure you put in there without any negative effects. Once you have sufficient activity within the bait stations, you can do the bait and switch and change that food lure out with a rodenticide.” Pre-baiting can help indicate where rodents are present and offer a more economical option when it’s time to actually bait by ruling out stations where rodents aren’t feeding. “You may go up to an account and you may have 50 stations at that account, and then if after pre-baiting, you have rodent activity in maybe 10 of those stations, then obviously, you want to put rodenticide in those 10 stations and maybe a few nearby stations.”

4. Know the different types of bait.

There are two main categories of rodenticides, Keefer said: anticoagulants and non-anticoagulants. These come in many forms, including blocks, pellets, liquids and soft baits, which Keefer said are especially popular now. First-generation anticoagulants are multiple feeding baits, Keefer said, which means rodents usually have to feed more than once to receive a lethal dose. “Some of the active ingredients include warfarin, and they work really well when rodents have high acceptance of the bait,” Keefer said. “But the problem with some of those is that there is documented resistance to those baits.” This can cause problems for the owner of the account, Keefer said.

Second-generation anticoagulant rodenticides (SGARs) are generally toxic to rodents in a single feeding, he said. These have active ingredients such as brodifacoum, difethialone and difenacoum. “They tend to be more effective, especially when there’s more food options available, because SGARs cause mortality after a single feeding event,” Keefer said. “There really hasn’t been any documented or scientifically demonstrated resistance to most of the SGARs. So these AIs inhibit coagulation of the blood, like the name suggests. It prevents clotting and it causes internal hemorrhaging.” And, he said, the good news for non-target animals is there is an antidote: vitamin K1.

5. Remember, each account is different.

Keefer said many companies just have one rodenticide and one formulation on the shelf. “Moreso true with rodents than say, maybe ants or cockroaches, every rodent account is different,” he said. “One size does not fit all. And I know that’s very cliche and people say it all the time, but that is ever so more true with rodents.” PMPs must understand the biology and ecology of the rodent they’re targeting with treatments and baits, he said. “Of course, you always need to follow that label, understand the label and even be familiar with the safety data sheet,” said Keefer. “And then, if you don’t know something, search for the answer and then ask questions to learn more and educate yourself as you move through this process of becoming an expert of rodents.”

The author is PCT’s senior editor.