Rat Ice: It's Complicated

The extensive burrow networks of Norway
rats in city parks have been hard to treat
safely, until now. (Photo courtesy of Matt Frye)

New York is planning to rely more on dry ice as a safer and effective treatment for rat colonies living in city parks.  But the logistics of labeling and marketing frozen carbon dioxide as a rodent control product have proved to be challenging.

Toxicity of carbon dioxide to rats is nothing new. When placed into a rodent hole and covered with soil, pelleted dry ice (frozen CO2) slowly evaporates filling the burrow with the gas and displacing the oxygen. Such treatments are low-in-risk for humans, leave no toxic residues, and pose no risk of secondary wildlife or pet poisoning.

Until now, the only barrier to its use was that dry ice was not registered as a pesticide and technically could not be used in commercial pest control. But last year, with the help of the National Pest Management Association, the rodent control product manufacturer, Bell Laboratories, agreed to work with the U.S. EPA to develop a label for dry ice pellets. The EPA, in turn, moved quickly last June to support the new "Rat Ice" label.

Unfortunately, as of today, Rat Ice is not available through any pest control supply distributor.  Of course, different forms of dry ice are readily available through many gas suppliers, liquor stores and grocery stores. But forget using over-the-counter dry ice. It's not legal.

Rat Ice will be a proprietary product sold as a conventional pesticide and distributed through normal supply channels along with a label.  For example, if your local pesticide distributor warehouse agrees to serve as a supplier, they will purchase and store the ice in special freezers and sell them just like any other pesticide.

According to Bell Laboratories technical rep, Scott Smith, Rat Ice will be sold in 1/2 and 3/4 inch pellets. Purchasers will be issued a label to place on their transport box, and will take from the distributor to the job site.

"Working with a perishable product like dry ice is complicated," Smith said. "We have retained a national distributor to transport the ice to local distributors, and plans are looking good on paper, but we fully anticipate some "aha!" moments ahead."

Challenges for Bell include enlisting distributors willing to handle inventory that literally evaporates if not sold soon enough.  Also, there's a question about whether PMPs will buy a product that is similar to one they could purchase at their corner grocery store. And how will pest control companies located far from big cities and big distributors get the product?

Smith is confident that a good system will be in place by the time Rat Ice hits the market. But it will take time.  Expect several months before product roll-out takes place, he said.

As someone who has struggled to find a convenient-to-use version of dry ice for research, I like the idea of the pelleted formulation. It will make application to burrows easier and safer.  And our industry has generally played well by FIFRA rules long enough, I believe the issue of "product swapping" will be minimal.

Rat Ice is no silver bullet, but it may revolutionize the way many PMPs and city health departments do rodent control. In tests conducted in 2016 by the City of New York, dry ice pellets inserted into rodent burrows reduced the number of active rat burrows in one park from 60 to just two. Another city park saw a reduction of 368 burrows down to 20. Impressive.

Cost for Rat Ice has not been determined, but the quick kill and low risk associated with this product should make it a popular option, especially for anyone who does a lot of Norway rat control.

If this concept works, and I hope it does, the PMP tool box may have to expand to include high-end coolers to keep your CO2 in solid form.  Just be ready to explain to your boss why you keep a Yeti® in your pickup.