Flying Pest Control: A Multi-Pronged Approach

At this time of year, we’re all grateful for the warmer weather finally making its way to these parts. Unfortunately, the rising mercury also gives rise to legions of nasty winged critters that buzz, bite and sting. All those flying insects can make life downright miserable for our horses (not to mention us!), and some can also be vectors of serious diseases such as West Nile Virus. It is therefore important to take steps to control the population of flying pests as much as possible. The best way to do that is to take a multi-pronged approach that makes use of both physical protection for the horse and environmental prevention strategies.


            Fly sprays are a key weapon for many horse owners in the war against flying pests. Most traditional sprays make use of pyrethrin, a chemical derived from chrysanthemums, or permethrins (also called pyrethroids), which are synthetic chemicals with similar neurotoxic qualities. Modern “heavy duty” fly sprays also often have some kind of agent to help the product bind to hair, allowing the spray to stay on for prolonged periods, even through rain and sweat. Some spray makers claim that their product will  last for two weeks or even longer, though such results do not appear to be born out in actual use. Says tack store employee Jenna Durban, of Palo Alto, CA, “I’ve tried just about every spray on the market, and the one I use says it works for 17 days, but I find I need to reapply it every seven days. Still, that’s a pretty darn good, and I want a product that lasts because I don’t have time to be out there spraying down six horses every day.”

            Though chemical-based fly sprays are a fairly effective means of physically protecting your horses from biting pests, some people are uncomfortable with the use of such products. Of primary concern are the potential health risks to humans, as well as possible damage to the environment. Recent studies have linked exposure to permethrins to an increased risk for Parkinson’s disease, and both pyrethrins and pyrethroids are classed as carcinogens. However, it is worth noting that there is no actual evidence of humans developing cancer as a result of exposure to these chemicals. States the U.S. Department of Health, “There is evidence from animal studies that pyrethrins and pyrethroids might be capable of causing cancer in people, but the evidence comes from animals that ate very large amounts of pyrethrins or pyrethroids for a lifetime.” Still, it is best to err on the side of caution when using chemical-based fly sprays, avoiding skin contact by wearing protective clothing, and using a dust mask to avoid inhaling air-born droplets.

             Those who want to avoid harsh chemicals altogether have the option of buying or making an all-natural fly spray. There are a number of commercial products on the market, and “home-brew” recipes abound on the internet. Such “green” fly sprays often contain ingredients like citronella, eucalyptus oil and tea tree oil. Many people swear by their favorite natural spray, but others have found them to be too short-lasting or simply ineffective. This author did an unscientific but interesting test using a popular green-bottle commercial product as well as three different home-made sprays, each applied liberally to ¼ of the same horse. The horse was then led into a mosquito infested field, and the effects observed. In the case of the commercial product, the mosquitoes bounced around above the horse for approximately three minutes before landing and biting. In the case of each of the home-made concoctions, they bounced around briefly or not at all. Ultimately, you must draw your own conclusions about whether a product is effective enough for your needs.


            For those who prefer not to use sprays but still want some kind of physical protection for their horses, fly sheets and masks are an excellent solution. Now better designed than ever before, the modern fly wear is light weight, durable and comfortable for the horse to wear. While some people are concerned that a fly sheet might make a horse too warm in hot weather, the light-colored, breathable mesh fabrics that most fly sheets are made of may actually help keep your horse cooler, especially if the horse has a dark coat. Furthermore, they offer a degree of UV protection, which is important if your horse has a sensitivity to sunlight or if you want to prevent the horse’s coat from fading.

            Fly sheets are available in a variety of styles to accommodate horses of different shapes and sizes, and there are even models designed with shoulder gussets and more flexible fabrics for horses that tend to be quite active in the pasture. Some offer belly panels to protect the horse’s sensitive underside, and you can also add fly-foiling neck covers, leg wraps and fly masks for total protection as needed. Many of today’s fly sheets offer the extra protection of fabric that is impregnated with long-lasting fly repellant that remains active through a number of washes.

            A recent addition to the fly sheet wardrobe are the ride-in fly sheets and masks.  Designed to connect easily to the saddle and bridle, ride-in products provide excellent coverage without getting in the way of the rider or inhibiting the horse’s movement. They are especially useful if you ride through heavily bug-infested areas such as meadows or marshlands. You may wish you had one for yourself! 


            In addition to physically protecting your horse from flying pests, it is wise to employ strategies to reduce pest numbers in the environment. Managing manure by collecting it and keeping it away from your horses, or spreading it thinly to allow fast drying are important control measures. Traditional approaches such as the use of fly traps and ridding your property of standing water are also helpful.  However, you may get the most dramatic results by making use of “biological controls” – living creatures that kill undesirable flying insects and/or their larvae. Any creature that kills large numbers of larvae before they have a chance to become adults and reproduce will be particularly effective.

            Because many of the flying pests of greatest concern have aquatic larvae, including mosquitoes, deer flies, black flies and no-see-ums (culicoides midges), aquatic biological control species are a great asset. Of course you still need to get rid of or treat standing water in places like old tires, rain gutters and buckets, but for larger bodies of water like water troughs and ponds, biological controls are a wonderful solution.

            For water troughs, large bird baths and ponds, your best bug eaters are fish. Many people already know about adding a few common goldfish or guppies to water troughs, but there is another species that may be even better. Similar in appearance to guppies, the mosquito fish (gambusia affinis) is a voracious consumer of insect larvae, and they are also extremely hardy and able to adapt to a wide range of temperatures. Some varieties have been bred to withstand temperatures down to –34C, so they can even survive the Canadian winter in many cases.  They are also aggressive towards other fish and each other, and thus tend to regulate their own numbers quite well. However, since they are so feisty, it is best not to add them in places where you already have other fish species present, and you should never add them to wildland ponds or waterways.

            Another biological option for ponds and other larger bodies of water is the humble tadpole. Tadpoles of both frog and toad species consume large numbers of aquatic larvae, and as an added bonus, the adults will eat flying insects of every description. The trick is to create an environment that will attract and sustain the amphibious hoppers and their offspring. Frogs need a pond with shallow edges so that they can get in and out easily. At least one edge should lead to rough, moist vegetation such as leafy mulch, as frogs require shelter from the heat of the summer sun. Though it is best to cut trees back away from a pond, part of the pond should be shaded, which helps the eggs reach maturity. A good variety of native pond plants will also attract frogs and give them a place to lay their eggs. Your pond should be located away from manure and other contamination sources such as runoff areas from composts, septic tanks and chemically treated fields and lawns. 

            Tadpoles can be transplanted successfully from wild ponds and other wetlands, but this is not legal in all locations and one needs to be aware of individual species’ requirements and natural status before attempting to take any from the wild. To find out more about transplanting or attracting frogs, you can contact the Metro Toronto Zoo’s Amphibian Interest Group or go to: 

If frogs or fish are not your thing, you can use mosquito dunks just about anywhere you have standing water. Mosquito dunks are solid blocks or tablets that contain a bacteria called Bacillus thuringiensis v. israelensis. The dunks float in water, slowly releasing the bacteria, which are then eaten by larvae. The bacteria will kill mosquito, deer fly, black fish and midge larvae, but they are harmless to non-target insect species, as well as to fish, amphibians, birds and mammals. They are considered safe for use in water troughs.  
For those more concerned about how to deal with flying pests and their larvae on dry land, is might be worth getting up a “poultry patrol”. Ducks, turkeys chickens and guinea fowl spend their days hunting all manner of insects and grubs on the ground, in the grass and in manure piles, making a significant dent in insect populations. Guinea fowl are particularly adept at bug gobbling, and they will also go after rats, mice and even snakes, while leaving crops and vegetation virtually untouched.

            Recent guinea fowl convert Carol Epps, of Langley, BC, was skeptical that the birds could make a real  impact, but now she says, “These things are bug-eating machines, I kid you not! Our fly population, which was pretty bad, is down to almost none since we got the guineas. One thing though – they are pretty loud when they are disturbed and do their ‘alarm’ thing, so if you or your neighbors are noise sensitive, you might want to try bantam chickens or something instead.” Though guinea fowl are quite hardy and low-maintenance, they and other poultry birds should have a protected area, preferably with a heat lamp, if temperatures get very cold in your area.

            One more option for controlling flying pests – specifically the annoying flies that breed in manure piles – are so-called “fly predators”. These are actually tiny, stingless, parasitic wasps that you buy in packets and add to your manure piles. The wasps seek out fly larvae, lay their eggs on them, and the wasp larvae then hatch and eat the fly larvae. Reviews on the effectiveness of this method of fly control are very mixed – some people have had great results, while others see little if any benefit. If you do decide to try them, be aware that they require multiple applications each fly season, and they are sensitive to extremes of weather.
Whatever methods you choose to utilize in your fight against the wicked winged ones, know that it is an ongoing battle, and that it is impossible to completely prevail. Therefore, keep an eye on your horses to check for signs of insect bite reactions and signs of illness that could be related to bites or stings. 

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