Rethinking Rodent Management

On Jan. 1, a new law took effect in California prohibiting many uses of second-generation anticoagulant rodenticides (SGARs).

Commonly referred to by its state Assembly Bill name, AB 1788, the law aims to reduce the risk of secondary poisoning to non-target wildlife like mountain lions, coyotes and birds of prey, which may eat poisoned rodents, by restricting the industry’s use of baits containing brodifacoum, bromadiolone, difenacoum and difethialone.

It was enacted despite the state’s burgeoning rat population. Last year, Orkin named Los Angeles the second-rattiest city in the U.S., with San Francisco earning fifth place, and San Diego moving up 13 spots to #19. The rankings were based on the number of new rodent treatments Orkin performed for residential and commercial clients.

Other pest management professionals saw requests for rodent control increase as well. “It was an influx of calls that I never experienced, not with my company or any company I’ve worked with, and I’ve been in the industry going on 21 years,” said Kat Herrera, owner of Kat’s Pest Solutions, which specializes in rat control in Los Angeles County.

The COVID-19 pandemic made the problem worse. Neighborhoods located near closed restaurants were “bombarded” with rats seeking food, water and shelter, even during the daytime, she said. Customers were scared and more properties needed exterior maintenance programs using SGARs because “the rats were going crazy,” recalled Herrera.

Kevin Mills, owner of Mills Pest Management in Burbank, Calif., agreed. “I’m not a big fan of baiting in general but there is a time and a place for it, especially lately because the rodent populations have been so bad, the rodents continue to be relentless, that baiting had to become more a part of my rodent control program,” he said.

Mills and other pest management professionals said rat behavior has been unusually aggressive. Determined to get indoors, the rodents have chewed multiple new openings in structures or chewed through sealed openings; they gained access to homes and crawlspaces through old sewer lines or by chewing holes in new plastic sewer lines.

“I feel like California officials and the public do not fully understand the rodent situation we currently find ourselves in. If they did, I would like to think they would have held off on passing AB 1788 and waited for a better time to implement it,” said Mills.

A GROWING MOVEMENT. PMPs said AB 1788 was driven by politics, not science. Even so, anti-rodenticide sentiment is becoming more than a California-only issue.

In June, activist group Raptors are the Solution, which sponsored AB 1788, called on the Biden Administration to place a national moratorium on the use of anticoagulant rodenticides (ARs) following an April 2021 University of Georgia study that found 83 percent of deceased bald eagles and 77 percent of golden eagles tested were positive for ARs.

In July, the province of British Columbia announced an 18-month ban on the sale and use of SGARs, with exceptions, to allow for a science review and promotion of SGAR alternatives. Proposed legislation in Massachusetts would require customers to sign documentation stating they understand the secondary poisoning risks associated with SGAR use. And discussions about eliminating or restricting the products are being held in some local municipalities and on social media.

“I think there’s definitely increased interest in it when it comes to the activist groups, but I don’t know if that’s necessarily translating into increased legislative success,” said Ashley Amidon, vice president of public policy at the National Pest Management Association.

Nonetheless, PMPs said customer attitudes about rodent control is shifting. A growing number of residential clients want rats removed but not harmed, while commercial clients are questioning the need to use SGARs on their properties.

“We’ve had customers in Oregon and Washington before even SGARs were restricted in California reach out to us asking about them and then coming to the conclusion that they didn’t want second gens used at their facility,” said Ashley Roden, a regional entomologist at Sprague Pest Solutions, which provides service in 10 western states, including California.

Roden said she is seeing more online articles appear in the Northwest about secondary transfer of rodenticide to non-target wildlife, and activists recently advertised their anti-rodenticide stance on billboards and buses.

“I think people are becoming more aware of what products are being used for rodents and they’re having more questions about it and our employees need to understand what product makes the most sense for their accounts,” said Roden.

IMPROVING STEWARDSHIP. As a result, pest management companies are adjusting their rodent management protocols.

In California, some have begun using first-generation and acute rodenticides in situations where trapping and rodent proofing aren’t enough to achieve control and where SGARs are no longer allowed. It’s not a simple product swap, however.

Alternative rodenticides typically aren’t as palatable as SGARs and PMPs feared rats would bypass these baits for the tastier food waste now filling trash receptacles as California restaurants reopened from pandemic shutdowns in mid-June. “The hot dog wins,” said Herrera.

First-generation and acute rodenticides also may require multiple feedings to achieve knockdown, a real challenge when faced with high rodent pressure.

To address these concerns, some companies have made comprehensive changes to their rodent control protocols, putting renewed emphasis on integrated pest management (IPM) principles.

They’re also hedging their bets, with AB 1788 potentially the beginning and not the end of rodenticide use restrictions. “This could be one step of many steps to come that limit the availability of those tools for us to use,” said Blair Smith, technical manager at Clark Pest Control, a Rollins company based in Lodi, Calif.

To prepare for this potentiality and to reduce the need to change protocol yet again in the near future, Clark Pest Control now requires any use of rodent bait to be justified by historical data or by current monitoring of rodent activity using non-toxic blocks. Armed with this data, technicians know when to implement a toxicant and if activity drops off, when to remove and replace it with a monitoring block in that station.

“The changes we implemented are an attempt to really drive home the IPM principles that we should be doing at all times,” said Smith. “Bait is a tool but it’s not the first line of defense,” she reminded.

Clark’s new strategy applies to accounts even where SGAR use is still permitted, including in Nevada where it provides service. “Even in a location where they’re still allowed to be used, we will not be blindly putting out rodenticide. We’ll reduce it back to a non-toxic block if the data shows that there aren’t rodents feeding on it,” said Smith.

Sprague Pest Solutions also revised its rodent management protocol because of AB 1788, in addition to an analysis of internal data that found the company was using more rodenticide in bait stations than it had stations with documented rodent activity. That underscored an opportunity to improve stewardship.

Sprague now takes “a more holistic view of rodent issues,” said Roden. Not all of the company’s locations are required to adhere to the California law, but trapping and exclusion take precedence and rodenticide use is not prescribed anywhere unless rodent activity is documented. The company has added first-gen and acute rodenticides to its product lineup and is training field staff on how and when to use these products. Previously, Sprague relied mainly on SGARs when rodenticides were needed.

“We’ve done lots of training this last year on rodenticides. You really have to know your product and the active ingredient in them,” said Roden. As well, technicians must understand rodent behavior and how that behavior influences product selection. The company is training technicians how to improve monitoring for rodent activity using monitoring blocks, snap traps, game cameras, remote monitoring devices, and “old fashioned” methods like flashlights to spot sebum marks, hair and droppings and flour and cornstarch to track footprints. Proper bait station placement also is a focus.

Other tools being used by PMPs to combat rodents include organic rat repellent spray, self-resetting exterior snap traps and rodent fertility control. No one tool promises to be the silver bullet. “Not even the second generations were silver bullets,” reminded Roden.

Customers ultimately may pay more for rodent control. “Our prices have had to go up,” said Herrera. Monitoring takes time and because some first-generation and acute toxicants aren’t single-feed products, she’s had to move some clients to weekly service. Callbacks are up and she’s had to make “repairs on top of repairs” at structures due to the intense rat pressure. The cost of materials and shipping has increased as well, she said.

Still, customers appreciate pest control providers who are prepared to address rodenticide concerns. “It makes customers feel better if you already have a plan; you’ve already thought about these things and you can talk to them about secondary transfer, how we’re mitigating that,” said Roden. “We need to be thinking about these things before our customers are.”

A DOMINO EFFECT? PMPs in California expect more rodenticide-use restrictions like AB 1788 to be enacted in the future. Exemptions to the law could be eliminated, as could the use of first-generation and acute rodenticides.

And with California being a bellwether state, other states and provinces could follow suit. “What starts in California ends up rolling across the country,” cautioned Chris Reardon, executive director of Pest Control Operators of California.

It’s too early to tell just yet how AB 1788 is impacting PMPs’ ability to control rodents in California, said Reardon. PCOC plans to gather data on rodent populations to help determine the impact.

In the meantime, PMPs expect the California rodent population to remain robust since using snap traps and currently approved rodenticides make it harder to crash these populations.

“I fear that it’s probably going to continue to get worse and there’s going to be some adverse consequences as a result,” said Mills, who performed more rodent work in November 2020 than at any other time in his company’s history.

This is particularly concerning from a public health standpoint. In 2018, Los Angeles experienced an outbreak of Typhus caused by infected fleas carried on mammals like rats. Cases of the disease continued to be reported through June 2021. The risk is greatest for people living in homeless encampments where rat populations are unchecked. The City of Los Angeles does not have a comprehensive vector control program to control rodents.

“I think PMPs will continue to stay busy with rodent work, which is great for PMPs but not so great for everyone else,” Mills said.

The author is a frequent contributor to PCT.