Equine Wellness
Insect Control
by Dr. Christine King
May 1, 2007

It seems to me that biting insects of all varieties are becoming more of a problem around the barn and on the trails; there are more of them, and they are becoming more resistant to insecticides and insect repellants. The cause of this problem, in my opinion, is threefold:

(1) excessive use of chemical insecticides, which has resulted in insecticide resistance in survivors, the same way that excessive use of antibiotics creates “superbugs” (multi-drug resistant bacteria)

(2) reduction in the insects’ natural predators (birds, bats, reptiles, amphibians, fish) because we’ve destroyed so much of their habitat around us

(3) too much manure (i.e., too many horses on too few acres) and too much standing water, also because we’ve so altered the natural landscape around us

Because this dilemma is multifactorial in the making, its solution also requires a multi-pronged approach. It’s all fairly self-evident, so I’ll comment on just three aspects that people ask about the most.

Natural Insect Repellants

Pyrethrins (natural extracts from the pyrethrum daisy) and essential oils (e.g., citronella, tea tree, eucalyptus, lemon, lavender) have long been the mainstay of natural insect repellants, and they are still effective. These products do need to be applied every eight hours or so for continuous coverage; however, effective insect control can be achieved with just once-a-day application if you time it right. For example, for problems with flies that annoy during the day, apply the product in the morning. For problems with mosquitoes or midges (gnats, no-see-ums, sandflies), apply the product in the late afternoon.

If you’re planning to go on a day-long trail ride or a weekend away, it’s a good idea to keep a small plastic bottle of insect repellant in your saddle bag or pack. You can either use a small spray bottle or apply the repellant to a cloth and wipe it on wherever it’s needed, on your horse and on yourself.

Essential oils are the primary ingredients in one of my favorite natural insect repellants for horses, “Zuffa Spray,” by EQUItelligent (www.equitelligent.com). Zuffa was developed by a local horse owner who has a very bug-sensitive horse, and it is made locally (which is another good reason to support it). Zuffa can also be used on human skin.

Insect Predators

Nature has already provided lots of predators for the common insects that plague us and our horses. It’s a good long-term strategy to find ways to encourage insectivorous birds, bats, reptiles, amphibians, and fish to live on or around your farm, as they are the insects’ natural predators. Most of these little guys need the protection of plants, so look into planting an insectivore-friendly garden near the barn if you don’t have undisturbed meadows and woodlands nearby.

Another option is to buy fly predators (www.spaldinglabs.com) and release them onto the manure pile. Fly predators are small insects that don’t harm animals or people, but that feed on the larvae of several different types of flies, including house flies, stable flies, and horse flies. Fly predators can be very effective at keeping the fly population down around the barn, although they usually need to be replenished every month or so—and they are susceptible to insecticides.

Garlic?

A lot of horse owners feed garlic to their horses, thinking that it’s a good insect repellant. Frankly, I’m underwhelmed by garlic as an insect repellant in horses. It works well in some horses, but not at all in others. There have been some studies that investigated the use of garlic as an insect repellent in humans. The general consensus is that garlic is worthless when taken orally against blood-sucking insects. It is, however, an effective insect repellant when used topically (as garlic oil), and an effective human repellant when taken orally.

Another thing to bear in mind is that garlic can cause irritation of the stomach in some horses. It can also cause red blood cell damage (Heinz body anemia), although both of these problems seem to occur only at high dose rates (higher than most horse owners feed).

In closing, let me encourage you to take a wholistic approach to insect control. As challenging as it can be to get started, the most effective long-term strategy for insect control is to learn a bit about the insects, their natural habitats and feeding preferences, and the ways nature has already devised to keep them under control. Natural and effective solutions will then present themselves.