10 Plants That Horseflies Hate 2023 [Updated]

Named for their tendency to be troublesome around horses and other large-bodied mammals, horseflies are pestilent members of the order Diptera (true flies). Like mosquitoes, only their females are known for targeting warm-bodied animals in order to obtain their blood for sustenance. These flies become fairly large and are remarkably agile as they flit from place to place. Once they are well-established, their populations can be quite challenging to eliminate.

Male horseflies typically subsist on a diet of plant juices and nectar. They favor warm, brightly lit areas located close to sources of consistent moisture. Horsefly larvae, which require semiaquatic conditions to thrive and develop into their adult forms, are known for being predators in their own right. If your farm or garden is outfitted with water features, some of which are stagnant, you might eventually find that you have a horsefly problem on your hands!

Fret not as there are various measures you can take to prevent or treat horsefly infestations – one of these involves growing the right set of plants and spreading them around strategic parts of the farm or garden!

The scent released by the oils of these plants, along with the predatory insects they attract, should help control the abundance of adult horseflies and reduce the hatching success of their eggs. Note that to be fully effective, however, the cultivation of these plants should be complemented by other environment-friendly means of repelling flies.

1) Citronella grass (Cymbopogon nardus)

Known for the strong aroma of its simple leaves, citronella grass is a remarkably important plant due to the insecticidal profile of its phytochemicals. When grown in large densities, its leaves emit a scent that keeps most types of flies, mosquitoes, and troublesome pests away. Unfortunately, its chemical makeup and tough structure make it unpalatable for most grazing animals. This means that, while it can aid in keeping pests away from the farm, your livestock will not be able to eat its leaves.

To increase the effectiveness of stands of citronella, it may be necessary to occasionally cut its leaves to expose their strongly-scented sap. You may also opt to use store-bought extracts of its oils to spread the insect-repelling scent around key parts of the home, barn, or coop. In many tropical areas that are often plagued with horseflies, citronella oils are incorporated into salves, candles, and infused coils that are intended for use as aromatic insect repellents.

Citronella grass thrives best in well-draining substrates that rarely become too wet or boggy. Make sure to plant stands of this species during warm periods of the year. If your farm or garden is located outside of its native range, aim to restrict its spread to within designated plots or containers.

2) Eucalyptus trees (Eucalyptus spp.)

Eucalyptus trees are rapidly-growing perennials that are often cultivated for their essential oils, their adaptations to forest fires, and their ornamental properties. These valuable plants come in a wide range of sizes, with some growing to just a few meters tall and others reaching remarkable heights of more than a hundred meters. There’s a single-stemmed species to suit just about any type of farm or garden.

One of the most biologically and economically important features of eucalyptus trees lies in their leaves. With surfaces that are densely covered in oil glands, eucalyptus leaves are rich in strongly-scented essential oils containing complex mixtures of protective phytochemicals. These repel dozens of pests and make the plant highly inedible to many grazers. In large quantities, the oils can be toxic.

Though koalas and several marsupials can tolerate and may even favor the oils of eucalyptus leaves, many insects and smaller animals can be adversely affected by their scent and taste. Horseflies tend to stay well away from anything that is infused with eucalyptus oils (including sprays, candles, and perfumes).

3) Peppermint (Mentha x piperita)

An extremely popular herb due to its culinary uses and ease of care, peppermint is a natural hybrid between spearmint (M. spicata) and watermint (M. aquatica). Like most species of the Lamiaceae family, the sap of this valuable plant is strongly scented. Its aroma is generated by its unique mixture of phytochemicals, some of which have insecticidal properties!

Peppermint is a frequent addition to herb gardens due to its rapid growth rate and its natural tendency to repel many types of pests, including true flies. The principal insecticidal components of its essential oil are pulegone and menthone, which can be used to treat various ailments. As the scent of these compounds is released only when the herb’s leaves and stems are mechanically damaged, it may be necessary to periodically prune your peppermint plants.

If you find that growing this mint hybrid is troublesome, particularly if it has the tendency to be invasive in your area, you may restrict its spread to indoor locations or to within dedicated containers. You may also opt to purchase its extracted oils and manually spread the scent around areas that are most likely to be infested with flies.

4) Lavender (Lavandula spp.)

The strong aroma of lavender plants, which is produced by volatile organic compounds (VOCs) in their essential oils, tends to confuse and repel insects. Horseflies will generally keep away from dense stands of these herbs. On its own, a single lavender plant may not effectively repel a considerable amount of flies or reduce the chances of pest infestations.

In addition to the insect-repellent scent of lavender species, their oils also contain chemical properties that can severely harm horseflies upon contact. For this reason, the extracted oils can be added to organic insecticidal solutions or directly applied to key parts of the home or garden. To compound their capacity to eliminate unwanted pests, they can be used in conjunction with eucalyptus and peppermint oils.

To fully utilize the repellent potential of lavender plants, aim to situate them close to areas where flies and other pests are most likely to congregate. Do keep in mind that these plants need full sunlight, a well-draining substrate, and proper ventilation to be effective. Suboptimal conditions can cause lavender to die back and attract its own host of pests.

5) Lemon balm (Melissa officinalis)

Lemon balm is a remarkably versatile herb that can double as an effective tool for the control of horseflies and other pests. Named for the lemony aroma of its serrated and bright green leaves, it grows to a full height of just 1 meter (3 feet). Its manageable size allows it to be cultivated in small to medium gardens and indoor locations.

In summer, the nectar-rich blooms of lemon balm are known for attracting hosts of bees and beneficial insects. Frequently grown as an ornamental plant and as a source of fragrant essential oils, this perennial and its byproducts have been lauded for centuries. Its oils are often combined with those of other citrus-scented plants to create a more potent and fragrant mixture with natural insect-repellent and pesticidal properties.

To keep horseflies and their close relatives away, aim to grow stands of lemon balm around patios, livestock pens, and other structures that often attract pests. To increase this herb’s effectiveness and ensure year-round control of horsefly populations, make sure to cultivate it alongside other evergreen herbs with insect-repellent properties.

6) Catnip (Nepeta cataria)

Though the essential oil of catnip is irresistible to some cats, causing them to exhibit behaviors that seem to indicate a sense of euphoria, it can spell disaster for many insects and smaller animals. Nepetalactone, the active ingredient in catnip essential oil, can cause insect paralysis and death by interfering with the basic functions of the nervous system.

Apart from the neurotoxic effects of catnip oil when it comes into direct contact with insects, its mere scent is enough to drive away nearby pests. If you’re concerned about horseflies attacking your cat as it plays outdoors, you might encourage your furry friend to roll around in a bed of catnip before sneaking out to explore! All manner of flies, ticks, and spiders should keep away from its scented fur.

To use catnip as a natural repellent for horseflies, cultivate it in areas where insects tend to congregate and mate. Note that, while its root system prefers to be regularly moistened, it will not do well in waterlogged substrates that are associated with periodically flooded ponds and streams. If needed, situate its stands in containers with a well-draining soil mixture.

7) Basil (Ocimum basilicum)

One of the world’s most popular culinary herbs, basil is cultivated for its phenomenal flavors and distinct scent. As it is an annual that grows rapidly in mild climate conditions, it’s a fantastic herb to cultivate in both temperate and tropical herb gardens. When sustainably harvested, its healthy stands can produce more than a year’s worth of leaves for use in a Mediterranean kitchen! Extra leaves can be plucked and incorporated into organic insecticides.

While basil may not be as effective as herbs like catnip at repelling pests, it is often cultivated as a choice herb due to its many uses. Its leaves can be used to make tea or tinctures that may be sprayed directly onto clothing or skin (on areas that flies and mosquitoes may target). Its essential oil can also be combined with other skin-safe and soothing oils, such as coconut or lavender oil.

Aside from producing aromatic compounds that may naturally keep horseflies away, basil produces blooms that can attract parasitic wasps. These are beneficial insects that parasitize the eggs and larvae of horseflies, preventing them from hatching and developing into their adult forms.

8) Tansy (Tanacetum vulgare)

Also known as ‘cow bitter’ and ‘golden buttons’, tansy is a perennial herb of the aster family (Asteraceae). It is easily identified during mid to late summer, which is when its distinctly yellow, button-like blooms arise in dense clusters on the tips of floral stems. Toxic due to the volatile compounds present in their essential oil, these produce a distinct scent that has been likened to that of camphor.

Tansy flowers and leaves contain thujone, a monoterpene that can cause convulsions and nervous system damage when it is consumed in large doses. This same compound is found in wormwood, sage, oregano, and mugwort – all of which are plants with well-studied insecticidal properties due to their complex essential oils. Tansy can thus be used as a natural repellent against horseflies and other pests.

Apart from repelling troublesome flies, tansy also contains chemicals that deter many herbivores and parasites. Interestingly, it was traditionally used in embalming and was later packed into coffins to prevent all manner of worms from aiding in the natural process of decomposition! Sprigs obtained from healthy shoots can be placed along windowsills to discourage flies from entering homes. Be wary of getting tansy oil on your skin, however, as it may cause contact dermatitis.

9) Garlic (Allium sativum)

Alliums are generally strongly-scented plants with a knack for repelling some of the most troublesome pests, and garlic is no exception. If you raise livestock or care for horses, you may already be well aware of the seemingly magical powers of garlic and its byproducts. Some garlic powder, for example, can be added into troughs with horse food to naturally repel all sorts of flies.

The insect-repellent aroma of garlic is attributed to the presence of sulfur in its essential oil. When cattle or horses ingest garlic, the sulfurous odor of its oils tends to be released by the animals’ sweat glands. This odor aids in preventing horseflies from landing on their coats and attempting to parasitize them. Thus, garlic is often touted as an herbal supplement that, apart from serving as an eco-friendly antibiotic and antimicrobial, repels flies.

Before you go off feeding your horses or cattle garlic, however, note that its ingestion may lead to complications in their blood chemistry. Instead, you may try cultivating garlic or spreading its cut cloves in areas that are prone to being infested with flies. You can incorporate harvested bulbs into a homemade, garlic-based insect-repellent spray for use around the farm or home.

10) Rosemary (Salvia rosmarinus)

Distinguished by its evergreen, needle-like, and leathery foliage, rosemary is a fragrant herb with a wealth of uses and benefits. In the garden, its hardy shoots can tolerate a wide range of conditions in mild to cool climates. Able to withstand winter temperatures (down to -20 ˚C or -4˚F) and tolerate brief droughts, it is a relatively slow-growing yet long-lived perennial.

Frequently cultivated for its culinary and medicinal uses, rosemary produces an essential oil with insect-repellent and pesticidal properties. Though its fragrant oil appeals to humans and adds delectable flavor to many Mediterranean dishes, it causes the leaves and shoots of the plant to be bitter and unsavory to grazers and plant-eating insects. Its oil contains a potent mixture of cineole, camphor, and several other phytochemicals that are toxic to flies.

To enhance the insect-repellent nature of your rosemary shrubs, aim to periodically prune their shoots to release a stronger aroma. You may use the cut sprigs as a garnish or as a flavoring herb for dishes. You can also combine them with bay leaves, sage leaves, and lavender cuttings to create fly-repellent herb bundles for use around the house or farm!