Horse-Friendly Fly Control

By Katie Shoultz


Mark Twain once said, "Nothing seems to please a fly so much as to be taken for a currant; and if it can be baked in a cake and palmed off on the unwary, it dies happy." But for the horse owner, it seems horses have replaced the cake, and the mere chance to annoy a horse is enough for a fly to die happy. Humans have devised a myriad of ways to reduce fly populations in barn settings - the most popular method of extermination being the traditional fly spray, but is this the most advantageous method in terms of the health of human, horse, and environment?

Say NO to toxic pesticides

A typical fly spray provides several warnings; the most common ones warn against contact with human skin, eyes, and/or clothing and against inhalation of the product. These warnings are present because of the pesticide(s) that are in the spray. Pesticides were first developed with an emphasis on long-term residual stability. This in turn led to chemicals that did not readily biodegrade, which can adversely affect the environment, especially in areas where it is used in high concentrations, such as a horse facility. The surrounding soil, water, and wildlife are all subject to exposure, and therefore, can be contaminated. These environmental toxins, if present in high enough concentrations, can induce illness in horses and humans because the toxins negatively affect the bodily systems. According to Dr. Joyce Harman, holistic veterinarian for Harmany Equine Clinic, certified in acupuncture and chiropractic, states, "Fly spray can be absorbed through the skin, though that is less of a problem, many times, than breathing, drinking or eating it. The new pour-on fly controls may have much more skin absorption, and there are no tested safe levels in horses."

In addition, many pesticides have a fairly long half-life, which is the time it takes for half of the substance to be eliminated through biodegradation. One such example is cypermethrin. Cypermethrin is quite common in fly sprays and is classified under pyrethroids, a group of synthetically derived pesticides. This synthetic pesticide is extremely toxic to fish and has a half-life of 16 weeks. Therefore, half of the amount of cypermethrin is still present after sixteen weeks. This lingering effect can wreak havoc on water sources and the soil, which in turn produces far-reaching effects of the environmental toxins.

Spraying systems should never be used since any product that is sprayed in a horse's stall will inevitably be inhaled and ingested by the horse numerous times. This is not healthy for the horse regardless of the product. As Dr. Harman states, "Overhead spray systems put regular doses into the water, hay and feed bins for the horses to eat, drink and breathe. The doses given in this manner have to be toxic."

Although using products labeled as 'natural' may seem alluring at this point, Dr. Nick Thompson - a holistic veterinarian who practices in the UK and specializes in homeopathy, acupuncture and nutrition for horses, dogs and cats - points out that a natural product does not equal a non-toxic product. For example, many products contain pyrethrins which are the chemical group of compounds derived from pyrethrum. Pyrethrum is derived from several species of the chrysanthemum flower, yet it is still considered a neurotoxin, a toxin that can damage or destroy nerve tissue. Dr. Thompson states, "Pyrethrin can be toxic. You have to remember that arsenic is also natural as is uranium, and you wouldn't want to take these in any quantity!"

Also, be aware of the other, or 'inert', ingredients. These are the ingredients that are not listed under the active ingredients category, however, 'inert' does not mean non-toxic. A person can request a Material Safety Data Sheet (MSDS) from the manufacturer or retailer. This sheet provides information on any known toxic ingredients that are in both the active and inert ingredients of the fly spray. Any combination of ingredients may increase toxicity as well.


Maximize health - minimize flies

Flies are not only a nuisance, but pose health threats. They are known transmitters of the bacteria Salmonella, as well as other viruses that can cause sickness in humans and animals. The best prevention against disease and illness is boosting immunity and maintaining good health, so it makes sense to minimize the flies in your horse's surrounding area in the most efficient and healthful manner. There are several alternatives and/or additions that one can implement to help reduce or eliminate the dependency on pesticide products.

Several pesticide-free sprays on the market offer a lower toxicity to humans, horses, and the environment. Most commonly, the active ingredients are a combination of citronella, garlic, apple cider, and vinegar. Several sprays contain extracts of various essential oils to help soothe any insect bites the horse may have gotten as well as conditioning the coat.

Dr. Harman recommends a trial and error procedure with these sprays stating, "Citronella, tea tree oil, pennyroyal and all the other essential oils that are used in natural fly sprays are effective. However, what I find is that the effectiveness of each is somewhat determined by the individual animal, as is true with most things in natural healing. So, try a natural product made with high quality ingredients (check with the manufacturer for quality control issues) and if it does not work for your horse, sell it to your friend for whom it might work perfectly and try one with different ingredients." On a cautionary note, a horse may still be sensitive to any one of these ingredients, in which case, it should not be used. A horse may display such symptoms as blisters, hair loss, swelling, and other changes in the horse's general appearance and behavior. Thus, regular daily inspection for any adverse reactions is always recommended.


Fly predators turn the attack onto the fly

Another biologically friendly and effective method of fly elimination is to attack flies at their source by using fly predators. Fly predators, also known as fly parasites, are highly effective in combating flies before they hatch. Unlike fly sprays, fly predators are able to prevent thousands of flies from hatching and reproducing. Fly predators are tiny insects, no bigger than a gnat, completely biteless and stingless (even though they are members of the wasp family), and are not a nuisance themselves. These fly predators control filth flies by inhabiting and feeding upon their larvae. In this way, a pest fly population can be greatly reduced. Since manure piles are a fly haven, this is the most obvious spot to place predator flies. The amount of fly predators needed depends on the number of horses - around 1,000 fly predators are needed per horse. Because flies reproduce more readily than the fly predators do, these numbers need to be supplemented/ replenished on a monthly basis throughout the fly season to ensure adequate pest fly control. The fly predators generally do not move far from the location they are placed in; therefore, if your farm has several fly hang-outs, it is best to deposit the predator flies in the various infested areas. The price is reasonable as well, running around $20 a month for five or six horses.

Also, it is desirable that the manure pile be deposited away from the area the horses commonly frequent, to manage the general radius the fly covers on a day-to-day basis. Although tedious, going around the horse's paddock and picking up the droppings every couple of days - especially if your horse is turned out 24/7 - greatly reduces the fly population in the field, leaving your horse much less agitated and free to enjoy his surroundings. Keep and maintain non-toxic surroundings that favor naturally occurring beneficial insects, as well as those that you are releasing. Dr. Harman also advises that the farm should have a good drainage system to avoid standing water that often attracts and provides a breeding ground for a variety of unwanted insects.


Horse-friendly fly traps, repellants, and deterrents

Fly traps are useful in controlling the flies around the barn or run-in shed, although be sure to check the label if wanting to avoid pesticides altogether as some do contain pesticides. Many of these traps contain non-toxic alluring scents that attract the fly and can be re-used; a clever tent-type trap uses an attractive color (see NHM Volume 6, Issue 4, Do It Yourself!) Make certain to tie the traps high enough or enclose them so that any curious equid does not attempt to play with, get caught up in, or attempt to eat the trap.

Sticky fly strips, banners, and wind-up tapes effectively trap flies, however, the disadvantages to them are that they usually become quickly covered with dirt, hay, and everyday barn stuff (including birds, other small beneficials, and your own hair!)

Adding small amounts of garlic and cider vinegar to a horse's feed is another method of fly deterrent. Dr. Harman suggests, "There is no need to over feed garlic; 6-8 cloves or a couple tablespoons of dried is plenty. Cider vinegar can be safely fed in almost any quantity; the best health benefits come from organic sources, but at least use vinegar made from whole apples. Doses often are 1/8 to 1/2 cup twice a day. You should stop feeding garlic for the winter to give the body a break, as garlic is an herb and it is good to give a break in the winter. Even the vinegar can be given a break in the winter." Dr. Thompson has had success using several other products in which he states, "Increasing B complex in the equine diet can help a lot. Homeopathic Staphysagria 12x sprayed onto the skin is also renowned for having deterrent properties."

Below is a recipe for homemade fly spray that Dr. Harman uses.


Fly Spray
With Witch Hazel as the diluent in a standard spray bottle, add 1oz. of any or a few of the below essential oils (but do not mix more than 3):

  • citronella
  • eucalyptus
  • tea tree oil
  • pennyroyal

Avoid spraying into eyes.

Fly masks have become quite popular in the past couple of years and their continued design improvements make them a great investment to keep flies out of eyes (and ears for those with ear coverings). A common fly that is discouraged by these masks is the face fly. These flies feed on the mucous secretions from a horse's eyes and nostrils, and can transmit diseases such as pinkeye to other susceptible herdmates while also ranking high on the annoyance scale. Fly masks may help prevent injuries that can occur on a horse's vulnerable eye area if he rubs his head on trees, fence posts, and other objects to rid himself of swarming flies. Select a properly fitting mask that will not allow flies to find a way inside - a trapped fly can be very unsettling to a horse. Inspect daily for holes or other damage from playful herdmates. If the horse is used to wearing the mask, allow time for him to get used to the onslaught of flies when it is removed (or have a repellent ready). Since riding leaves a horse open to a fly onslaught for an extended length of time, the mask can be placed over the bridle if the fit remains suitable and will not let flies in.

Fans that are placed throughout a barn, in a shed, or in an indoor tend to help deter flies as well, and the breeze is certainly nice on a hot day! Extra large fans are available for installation in sheds and indoor arenas as well. Stable fans can be placed to direct air above stall walls or at ground level; ceiling fans are also an option for some structures. All fans, electrical cords, switches, etc. must, of course, be out of the reach of any horses, and properly and safely installed. Fans can provide a huge relief from the flies as well as much needed circulation during humid weather.

Flies do have a place in Nature too, but if they become out of control there are natural ways to re-establish the balance. Any, or a combination, of the above alternatives will likely prove successful in thwarting the ever present fly to make life for both you and your horse a little more comfortable and healthy. The decrease in pesticides alone will inevitably help to make your farm more environmentally friendly. Just make certain to double-check that cake as the flies may have to resort to their old hang-outs.

Many thanks to Dr. Joyce Harman and Dr. Nick Thompson for their helpful expertise.


About the author:

Katie Shoultz is a freelance writer, and after using herbal and aromatherapy remedies to successfully restore her older mare's vitality, she has become dedicated to promoting natural health care methods for horses.


Joyce Harman, DVM, MRCVS
Harmany Equine Clinic, Ltd
PO Box 308
Flint Hill, VA 22627


Nick Thompson BSc.(Hons), BVM&S, VetMFHom, MRCVS
Holisticvet Ltd.
Weston Chiropractic Centre,
Bath, BA1 2XT, UK
Phone: 08700 111 340