When we started our research on ridding barns of rodents, we were bombarded with information on preventing them. Yes, of course, we know what we’re supposed to do to prevent them:

Use secure metal feed containers. 

Clean up spilled feed right away, using a damp cloth to wipe it up. 

Store alfalfa pellets as securely as sweet feed. 

Fix broken feed room windows or boards promptly, and if you see holes in the siding or walls, seal the areas. 

Screen off vents.

Remove garbage.

Cut away shrubbery growing close to the barn walls and doors.

Feed your barn cats (see sidebar).

Feline Patrol

Good mousers are well-fed, comfortable and content. Love ’em or hate ’em, barn cats are your best bet for keeping down the pest population in a stable.  The cat should be spayed and vaccinated regularly and remain on a stringent deworming schedule so that he does not become a potential disease carrier due to contact with various species of rodents. And you feed your barn cat. A hungry cat is going to head to the easy-picking fields for mice rather than spend time stalking one hiding in the barn. Mice and rats carry viruses and bacteria.  They transmit salmonella, leptospirosis, trichinosis and rabies. They spread mites, ticks, lice, fleas and internal parasites. Their droppings are disgusting, and they can nibble through leather goods and plastic containers.  A barn of 100 rats can lose over a ton of feed in one year to these hungry rodents. This doesn’t include feed that has been spoiled by rodent urine, droppings and hair. Mice and rats use electrical wires, vines, shrubs and trees to get into a barn. Once there, rodents damage building structures and may cause irreparable losses due to fire as a result of gnawing through wire insulation, exposing the live wires.

Admit There's a Problem
But what if the rodents have already invaded the premises? First, determine what’s going on. Clues to rodent problems include chewed surfaces, droppings and new holes in walls and corners. Ronald Dues, who owns DSI Pest Control in Stuart Florida, has horse-barn clients.  He says rodents prefer to be active at night, so if they feel secure enough to roam in the daylight, there are many.

Consider baiting and trapping by a professional. A pest-control company will identify the rodents and use the correct bait to alleviate the population. They’ll remove the carcasses and dispose of them. Get one that has worked around horses before and check horse-barn references.

Horse owners are understandably concerned about rodent bait, which is, after all, poison. Bait stations are generally tamper-proof and can be placed out of reach of the horses.  However, dogs and cats may be at risk, so make changes in their handling or place the bait stations out only in the evenings, when horses are in their stalls and pets are locked up.

Energetic barn owners can handle problems with the help of an agricultural agent who can identify the rodent population and help choose the bait, since, for example, the Norway rat is a meat-eater, while the roof rat prefers grain. Find out how to dispose of the carcasses properly.

Dues recommends zinc phosphide, or tracking powder, made by Bell Labs, sold as ZP Rodent Bait. It goes into a sealed container with an entrance and exit hole. The rodents track through it and take the poison back to the nest, eliminating the colonies.

Traps
If you don’t want to use poisons, traps can be used. Place traps near nests.  Professional wildlife trappers may also help with your problem (and they’re the ones to call if you’re dealing with small animals like opossums or raccoons).  They typically don’t use poisons but trap animals and then seal any access points in feed rooms and haylofts.

Sean Carruth, of Critter Control, a national wildlife trapping company, says you may never be able to completely rid a barn of rats and mice, as the number of entrance points is too vast. Rodents require only a half inch space to access any building. This means a constant watch on making your barn as unattractive to pests as possible.

Monitor potential entrance points for activity by stuffing newspaper in the holes or by lightly taping paper over them to identify if they’re still active. Once the holes are no longer active, seal them with caulk, wood, aluminum, CopperStuff-it or hardware cloth, to prevent the use of that entrance point again.