Eco-Friendly Pest Control

Environmentally friendly options for pest and rodent control in the barn include hygiene efforts, trapping, and biological controls.

Poison, poison everywhere. While this has been a solution in the past for the problem of rodents, flies, and other pests, today many horse owners are trying to find less potentially harmful ways to control vermin than the perennial pesticides. Not only can these chemicals be harmful for the environment and any pets or livestock that might ingest them, but they also can kill the beneficial insects that are flies' natural predators. Flies also are becoming more resistant to many pesticides after generations of exposure, according to entomologists. Keep your farm's rodent and insect populations in check with the eco-friendly options we'll describe.

Rodent and Varmint Control

According to Shea Porr, PhD, assistant professor of equine science at Virginia Tech's Middleburg Agricultural Research and Extension Center, diligent cleanliness is the first line of defense against rats and mice. If the barn is clean, rodents won't be attracted to spilled feed or tempted to establish nesting sites convenient to this veritable buffet.

"Having snug, well-fitting doors on tack and feed rooms can help keep pests out," says Porr. Check walls, flooring, and ceilings for cracks or separations where rodents might come through--especially in corners or around water pipes or vents. These holes can become a rodent freeway. If there's space under any door, add a threshold that meets the door more closely.

Seal any cracks wider than ¼-inch. Mice can wiggle through an amazingly small space; any place they can stick their head through, they can get their body through. Poke coarse steel wool into small holes in floors, walls, corners, or odd-shaped crevices, as mice won't chew through it. They can, however, chew through calking material or spray-foam insulation. For larger holes use lightweight sheet metal or fine mesh wire screen, nailed into place.

Jenifer Nadeau, MS, PhD, associate professor and equine extension specialist at the University of Connecticut, says you can't close off soffits or other openings important for ventilation, but you can cover them with wire mesh.

Also, don't underestimate the pest- preventing potential of a simple sweep with the weedeater. "It ... helps to eliminate brush weeds and grass around your buildings," says Nadeau. Then rodents won't have protective cover and hiding places around the buildings' exteriors. Don't store hay or straw in or next to the barn; a stack of bales creates ideal hiding/nesting places.

When disposing of spilled grain, soiled bedding, or any other debris, haul it away from the building so it won't attract nearby rodents. Store tack and horse blankets up off the floor, as a heap of cloth or leather items makes a wonderful hiding place for rats and mice. A rodent-proof tack room is best, but if that's not possible, tack can be stored in a well-sealed trunk or cedar chest (which not only keeps out mice but also deters moths and insects).

"When storing blankets, pads, bedding materials, etc., it helps to move these periodically, to deter or disrupt nesting activity," says Nadeau. Use an organized system of hanging on the wall, rather than piling on the floor.

Although tack and equipment storage is important, "keeping feed in closed bins is probably your best deterrent," says Porr. "Containers made of metal or heavy plastic (that rodents can't chew through) that are covered and cleaned regularly will help. Don't leave bags (of feed) out where rodents can chew them. A good barn cat can also help," she says.

According to Thomas Barnes, MS, PhD, wildlife extension specialist at the University of Kentucky, proper barn hygiene and feed storage also are the best means of deterring larger varmints such as opossums and racoons.

Using Traps

Inexpensive wooden-base snap traps (rat or mouse size) can be effective for rodent control. Mice are easy to trap because they're less suspicious than rats and more attracted to bait. It takes more strategy and persistence to catch elusive rats, and Barnes says they can be extremely difficult to control without poisons.

The best tactic is to use several traps (sized according to your type of rodent infestation) and place them wherever there's evidence of rodent activity (e.g., droppings, signs of gnawing). "Look for the oily spots where they're going in and out of a hole or rubbing against wood, and place sticky glue traps along their travel areas," says Barnes. "Glue traps are easier to work with than snap traps, though you have to deal with the animal once it's been caught."

"You don't need expensive commercial (glue) traps," he adds. "You can buy the sticky chemical (nontoxic polybutene) to spread on cardboard to make your own sticky traps. If you don't want cats, dogs, or horses stepping on sticky traps, put them inside a PVC pipe of proper diameter for the rodents to go through them." According to Barnes, rodents like to travel through small areas because they feel safe when doing so.

If you decide to use bait in your traps, Barnes suggests a mixture of peanut butter and oatmeal. "Rodents are attracted by the odor of peanut butter. Make a bait ball and put it in the middle of a piece of PVC pipe and then place glue traps on either side of it," he says.

Position snap traps so a rodent must travel directly over the trigger. "A trap along a wall should extend out at a right angle, with trigger end touching the wall along their runway," says Barnes. Rodents use whiskers as feelers to follow the wall and are likely to feel their way around a parallel trap rather than walk over it.

"When using any kind of traps, put them in pairs," he advises. "If a rodent jumps over the first one he may land on the second one."

If a rat is too suspicious to try bait, use a muskrat trap covered with a small piece of cloth. Anchor traps securely, using wire to secure snap traps to overhead rafters, beams, or pipes when trying to catch pack rats or roof rats.

"There are humane live traps if you don't want to actually kill the rodents, but you have to check these often," says Nadeau. While traps are safer than using poison, they are more labor intensive. You must check them daily and reset or rebait them, removing any dead rodents.

Other traps include flip boxes that toss mice into an escape-proof container when they pass over a triggering mechanism or enter a hole in the side of the box.

"Some methods don't work for controlling rodents," cautions Barnes. "For instance, ultrasonic devices don't work at all. There are no repellents that actually work."

You'll never completely eliminate a rodent population, but you can reduce it to a manageable level if you are diligent. And as long as the rodents keep moving in, you must continue control strategies.

Because such products are not only poisonous to pests, but also to horses, dogs, and other animals, "most people are against using rodenticides, but if you have a bad infestation, trapping may not be enough," says Barnes. "You may have to hire someone to use rodenticides to clean out the rodents and get the population down to where you can then keep it down to a manageable level with other methods." However, this should typically be used a last resort, he notes.

If dealing with larger invading critters such as opossums and racoons, you might solicit the help of a certified wildlife operator. "Opossums are quite easy to trap using a sweet and fishy bait in any type of live trap," explains Barnes. "Raccoons are much harder to deal with as they don't necessarily like live traps ... In some cases raccoons can become trap shy if they have been partially caught, and then it is almost impossible to catch them again."

Barn and Pasture Fly Control

Now that we've addressed the pests that scurry, let's discuss the ones that flutter. Fly traps and biological controls, along with good manure management, can be effective in an integrated pest control program. Good sanitation practices are the best way to eliminate breeding sites for flies that mate in manure (houseflies, stable flies, horn flies, etc.).

"The flies need moisture to breed," says Nadeau. Therefore, manure piles should be covered to prevent flies from breeding in them. A compost pile, on the other hand, should be left uncovered. Several universities have done studies on the pest ramifications of leaving compost piles ¬uncovered.

"We're doing some static composting research right now, to see how management- friendly composting can be," says Porr. "We have a pile that's been in compost since December 2009 and had no fly problem on that pile, and we only turned the pile a couple of times during that ¬period."

Another benefit of this management method, of course, is that "once it's had time to compost, manure makes good fertilizer," she explains. "Then you can spread it on fields and pastures as fertilizer, without spreading parasites or flies." Thus, composting is another way to reduce fly load on your farm.

"If you do it correctly, and the temperature of the compost gets over 130ËšF for three or four consecutive days, this will kill parasites and fly eggs," says Porr.

Fly traps can also be helpful. "One type of homemade fly trap utilizes a milk jug with bait (usually ripe fruit) inside. The flies get in and can't get out," says Nadeau. "Sticky traps (made with a ¬nontoxic sticky tape substance) also work, if replaced ¬regularly."

Another environmentally friendly trap for biting flies (horse flies, deer flies, stable flies, black flies, mosquitoes, etc.) uses the insects' natural attraction to large dark objects (similar to the shape and silhouette of an animal) against them. One particular trap (The Epps Biting Fly Trap, shown on page 27), for instance, simulates with transparent sheets of plastic the air space above an animal and under its belly--where flies normally circle before landing to bite and feed. When flies hit the sheets they ricochet into trays of water below and drown.

Biological Control Methods

Bill Clymer, PhD, entomologist and consultant in Amarillo, Texas, reminds us that biological control was the first fly control we had before the advent of pesticides. We depended on insect predators such as wasps to feed on fly larvae, dung beetles to disrupt successful insect breeding in manure, and on birds and bats to eat adult insects.

Porr notes that some people report success using parasitic wasps as fly control. "You can order these online, and they are delivered monthly to be spread on manure and compost piles," she says. "These tiny wasps lay their eggs in fly larvae. The hatching wasp larvae eat fly larvae." For this tactic you need an adequate amount of wasps for the amount of waste being produced by the horses on your farm.

"The drawback with depending on this type of fly control (or any, really) is that flies can still come from surrounding farms that are not controlling their fly populations, and you may not see much beneficial effect," Porr explains. "The wasps are inexpensive, compared with (the cost of) continual use of sprays, insecticides, and repellents."

Clymer offers insight on dung beetles, which essentially help control manure loads in pastures, eliminating breeding sites for flies and parasites: "We have data showing that a large population of dung beetles can decrease internal parasites of horses by about 95% and external parasites that breed in manure by about 90%."

While parasitic wasps can be ordered from several suppliers, there are fewer sources for dung beetles.

"They may not work as well, if they're not a species adapted to your region," says Clymer. "Australia has 26 imported species (from Africa) that are very effective in removing manure, but when the U.S. started this program we only got about one-third that number, so we don't have as much variety to choose from. You have to put out large numbers and it may be two or three years before you get a good population established and see good results."

In addition to the parasitic wasps, many other creatures in nature prey on pesky flies, especially various bird species. "In earlier years chickens and other fowl in barnyards were a major factor in keeping fly populations down," says Clymer. Some people still use chickens or ducks for this purpose.

Take-Home Message

Eco-friendly and chemical-free pest control methods not only help keep your property and animals healthy and happy, but they also combat disease spread by rodents and flies. Experts recommend keeping a tidy barn environment and watching for telltale signs of unwanted visitors, along with using traps and deterrents. Contact your local extension agent for more pest control tips and strategies for your area.

About the Author

Heather Smith Thomas

Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog,, she writes a biweekly blog at that comes out on Tuesdays.

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