Do-It-Yourself Rat Control
Part 2: Chemical Rat Control (Poisoning)
Note: Setting poisons for rats is a hazardous activity that is best left to professionals. The following information is presented for informational purposes only. Always be sure to read and follow all label instructions when using any pesticide product. Baiting should be looked upon as an adjunct to exclusion and trapping, not as a replacement for non-chemical measures.
Disadvantages of Using Rodenticides
Controlling rats by with rodenticides has a number of disadvantages:
Poison baits designed to exterminate rats are often toxic in varying degrees to humans and other animals. Although the amount of rodenticide that would be needed to kill a larger animal is usually more than than that needed to kill a rat, nonetheless many domestic pets and other non-target animals, and occasionally humans, are accidentally poisoned by rodenticides every year.
Some (but not all) rodenticides exhibit secondary toxicity, which means that the a poisoned rat may itself be toxic to other animals. If another animal (like a dog or cat) eats the poisoned rat or its carcass, that animal in turn may be poisoned by the rodenticide remaining in the rat's body.
Because it may take several days for a rat to die after eating most rodenticides, poisoned rats can die inside wall voids or other inaccessible structural elements of a building. Aside from the stench (which can be overpowering and may last for several weeks), rat carcasses serve as a breeding medium for flies and other pests.
Displaced ectoparasites like fleas, ticks, and mites will often seek new hosts when the rat they were parasitizing dies. Many of these parasites are vectors of potentially serious diseases.
Advantages to Using Rodenticides
When used properly, rodenticide baits have several advantages as part of an effective rat control program. For example:
Rodenticide baits enable effective control of even large rat populations where trapping would be impractical.
Using weather-resistant baits in tamper-resistant bait stations provides longer-term, wide-area control with minimal maintenance.
Rodenticide baits in tamer-resistant bait stations can be used outdoors, whereas few rat traps are suitable for outdoor use.
Professional exterminators usually use rodenticides primarily in rat-prone exterior areas, or inside buildings whose construction is such that dead rodents are unlikely to be trapped in inaccessible areas.
Proper Use and Placement of Rat Poisons
The single most important part of using rodenticides is to make them inaccessible to children, pets, or non-target animals. The best way to do this is to use tamper-resistant bait stations.
Using bait stations not only reduces risk; it can increase effectiveness. Rodents are prey animals whose lives depend on avoiding predators. Bait stations provide a protected, enclosed place in which rodents feel more secure -- and in which they are more likely to eat a lethal dosage of bait. Rats are also finicky and won't readily eat spoiled food. Bait stations help keep the rodenticide fresh and palatable.
Bait Station Placement
The placement of bait stations is similar to that of traps. The stations are secured in place along rat travel paths. The rodenticide bait is then secured inside the station, and the station closed and locked.
Bait stations installed inside buildings may be secured using screws, nails, or construction adhesive. Exterior bait stations can be secured by attaching them the exterior walls of a building, or they can be secured to the ground using stakes, lag anchors, or earth anchors. All bait stations must be sufficiently secured that a child or domestic animal cannot move, shake, or open them.
Exterior bait stations are typically mounted along exterior walls of buildings, along fence lines, along wharfs and piers, and in other rat-prone areas adjacent to structures. They can also be anchored to the ground adjacent to rodent burrows, hidden in ground cover near shrubbery, under sheds, and in garbage storage areas. They should not be used in areas frequented by children or in places likely to be flooded.
Almost all of the rodenticides available to unlicensed individuals are anticoagulants. These baits are widely considered to be the less hazardous than other types of rat poisons because they are slow-acting and because they are more easily antidoted in the event of accidental ingestion. One of the better ones is Just One Bite Rodenticide, whose active ingredient (bromadialone) is the same used in many professional rat poisons.
Paraffinized anticoagulant baits come in a variety of shapes and sizes to fit popular bait stations. Baits sealed in paraffin are more weather resistant than grain or meal baits, less likely to be tracked by rodents through sensitive areas, and may actually be better accepted by rats because they provide something for them to gnaw on.
Whatever bait is used, however, poisoning should be looked upon as only a small part of an overall rat control program. Sanitation, harborage reduction, and exclusion are the real keys to long-lasting protection against rodents.