Deer Fly Control: How to Get Rid of Deer Flies

This page is a general deer fly control guide. Using the products and methods suggested, you will get control of deer flies. Follow this guide, use the recommended products, and we guarantee 100% control of deer flies.

Many homeowners who work or spend time outside know when summer is here with the presence of painful bites, especially from deer flies. These pests are common throughout the United States, particularly in the southwest. Like horse flies, they have razor-sharp mouths that inflict quite a bit of pain and blood spillage. Though horseflies and deer flies belong to the Tabanidae family, they are each their species. Deer flies are in the genus Chrysops, whereas horse flies are in Tabanus.

Although their name suggests they feed on deer, this pest feeds on various hosts, including people or cattle. While the males feed on plant nectar and pollen, the female deer fly is focused on ingesting blood to provide the nourishment needed to produce her eggs. These aggressive eaters are hardly discouraged by passing people or animals and will bite multiple times until they attain enough blood.

Numerous populations of deer flies can interrupt grazing for livestock animals and make it hard for homeowners to enjoy their yards with these painful attacks. In addition to blood loss, these pests can transmit diseases from infected to healthy animals. To get rid of deer flies plaguing your yard and animals, follow the steps and recommended products throughout this easy-to-use DIY guide.

Identification

Before proceeding with treatment, you must identify and ensure you are facing a deer fly infestation and not another kind of fly. Careless identification can lead you to use the wrong or ineffective insecticides, which can waste time and money. Here are some key characteristics of deer flies to learn to differentiate them from horse flies and other flies.

• Deer flies are smaller than horse flies yet larger than house flies at 1/4 inches long. Horse flies are larger at 1.25 inches in length.
• Large flies with broad bodies and bulging eyes that are patterned gold or green.
• Large and thick three-segmented antennae have their thorax and abdomen covered in fine hairs.
• Yellow-brown to black in coloration, they have bee-like stripes on the abdomen and dark bands on their clear wings.
• Female deer flies have large, prominent mouthparts that have a scissor-like appearance to cut skin.
• Lay large batches of 100 to 800 eggs either in a single layer or in 3 to 4 high tiers. The eggs are cylindrical in shape and white in color, but they gradually darken to gray, brown, or black.
• Deer fly larvae are fairly straight and worm-like in shape with tapered ends. They have 11 to 12 segments in the body, are legless, and are tan, white, or brown. They are 3/4 to 1 1/2 inches long, smaller than horsefly larvae.

Use the image and description above to help you correctly identify a deer fly. If you are unsure of the pest infesting your livestock and property, contact us by phone, email, or in person at one of our store locations. A photo or sample of the pest in a sealable plastic container or bag can help with proper identification.

Inspection

Once deer flies have been confirmed on your property, you can proceed with the next phase of control, which is inspection. During this phase, you will focus on finding areas where deer flies are most active and the conditions allowing the pest to thrive.

Where to Inspect

Deer flies particularly like sunny places near moist areas like swamps, edges of water bodies like ponds and streams, and neighborhoods or suburbs near wooded, wetland environments. In more rural areas, they are most active in fields and pastures near water sources and used for livestock. Usually, deer flies will not enter barns, stables, and other shaded areas due to difficulty seeing dark, moving objects for them to feed upon.

Deer flies lay their eggs on grasses and vegetation like cattails or sedges around ponds or other water sources. In their adult form, the deer fly rests on shrubbery or tall grasses until it finds a person or small to large mammals like horses, cattle, deer, dogs, or birds to feed on.

What to Look For

Deer flies only feed during the day and focus on animal or people's movement and carbon dioxide output. When selected, the female deer fly will fly in a fast, noisy circle around their selected victim. Besides the noise, these pests can be noticed by their painful bites. When deer bite animal flies, it can be seen with consistent tail and head swishing to remove these biting flies. Once bitten, these pests can leave behind red bumps or welts. 

In contrast to horse flies, which bite mainly around the legs of stationary hosts, the deer fly will bite on the shoulders, head, and neck areas of moving hosts.

Treatment

Wear personal protective equipment (PPE) such as long-sleeve shirts, long-sleeve pants, and a hat, as bites from deer flies are painful and can cut skin.

Deer flies are most active from May to September when the weather is warm and humid. To get rid of deer flies, you will need to implement several yard maintenance tasks and fogging with a residual insecticide prior to or at the beginning of periods of activity. Fogging or any pesticide control with common pyrethrin or pyrethroid insecticides will be useless without cultural control.

Step 1: Mow Tall Grasses

Deer flies are most active during the day and generally rest at night or take short naps on tall grass blades or leaves when no host is available to feed on.

Once the grass reaches a height of 3 inches, keep your lawn and fields trimmed with regular mowing. Adjust the mower blades on a higher setting when mowing during the summer. This will help limit places for deer flies to rest or hide on your property.

Step 2: Fog with Flex 10-10

For total control of deer flies, a pyrethroid can be used as a fog or mist application, like Flex 10-10. Flex 10-10 is an emulsifiable concentrate that kills deer flies and insects as a fog application with ULV cold foggers, fog/mist generators, or a backpack sprayer. Made with 10% permethrin and 10% piperonyl butoxide and classified as a pyrethroid chemical, this product will affect the deer flies nervous system, leading to paralysis and death.

When fogging, it is best to wear personal protective equipment (PPE) to protect your entire skin, eyes, and mouth. For a dependable and high-volume ULV fogger, we recommend the Tomahawk TMD14 Backpack Fogger. Calculate the square footage of the treatment area to determine how much Flex 10-10 to use for your treatment area and sprayer. To do this, measure the treatment area's length and width in feet, then multiply (length X width = square footage).

For low infestations of deer flies, dilute 4 teaspoons of Flex 10-10 per gallon of water (1:200) to make a 0.05% permethrin ready-to-use product. For severe infestations of deer flies, use 8 teaspoons of Flex 10-10 per gallon (1:100) to make a 0.1% permethrin ready-to-use product. For a 1:100 dilution, mix 11.6 fl. oz. of Flex 10-10 per 10 gallons of water.

Fill the sprayer reservoir with half the water, add a measured amount of Flex 10-10, and pour in the remaining half. Secure the lid to the tank and shake to ensure even agitation. Pump the primer bulb 3 to 5 times, then adjust the engine's choke position to UP and move the throttle into the ON position. Pull the engine cord until it starts, then once it does, move the engine's choke to the DOWN position.

Direct the spray nozzle towards your lawn (not used for grazing), cattle barns, horse barns, stables, paddocks, dairy and beef barns, poultry houses, swine housing, animal quarters, and other listed livestock or animal housing areas. Do not spray near swimming pools, water bodies, and areas where food is stored or prepared.

Do not enter or allow people and animals to enter treated areas until vapors, mists, and aerosols have been dispersed, the area has been thoroughly ventilated, and the sprays have dried. When used in dairy barns or facilities, Close milk bulk tank lids to prevent contamination from spray and dead or falling insects. Remove or cover milking utensils before application. Wash animals' teats before milking.

Prevention

After eliminating the deer fly infestation, you must ensure these pests do not return. Deer flies are persistent pests that will seek the smallest opportunity to reinvade your property, so diligent preventative measures are needed. Otherwise, pesticides are not completely effective. Remember the following preventative practices to ensure deer flies do not return to your yard.

• Eliminate weeds with appropriate herbicides and mow when turf exceeds 3 inches in height to eliminate hiding places for adult deer flies. Prune overgrown foliage and shrubbery near your home and barn, as these could also be used as resting sites for this pest.
• Get rid of weeds like cattails around the edges of ponds with aquatic herbicides like Ecomazapyr 2 SL Herbicide. This will limit habitats and feeding sources for deer fly larvae, thus eliminating future generations.
• Limit moisture in your yard by covering muddy areas and holes in the turf with dirt or other organic material until dry and filled. If the land is creating gaps or holes for water to gather, level it.
• Build sheltered areas like barns, sheds, and dog houses or place dense trees out in fields for animals to escape the sun and provide shaded areas since deer flies commonly avoid these sites.
• Remove ponds, water bodies, or other swampy areas in or nearby your home and barn to limit the moisture needed for deer fly larvae. If these sites cannot be removed, then be prepared to relocate your animals.
• Apply fogging treatments with Flex 10-10 in labeled areas where deer flies swarm and reapply as needed or before periods of activity.

Key Takeaways

What are Deer Flies?

• Deer flies are relatives of the horse fly and are known as true flies that vigorously feed on the blood of animals and people.

How to Get Rid of Deer Flies

• To kill deer flies on your property, you will need to remove any overgrown foliage and weeds in your yard and around your pond or other water body sources. Mow your yard for tall grass blades exceeding 3 inches in height and remove aquatic weeds around your water body edge with Ecomazapyr 2 SL Herbicide. Once these environments are taken care of, you will then apply Flex 10-10 as a fog treatment.

Preventing Deer Flies Reinfestation

• Repel deer flies from your yard and livestock by mowing, aquatic weed treatment with Ecomazapyr 2 SL Herbicide, limiting moisture in property by sealing holes or addressing the cause of flooding, building sheltered areas that provide shade for animals, and continual applications of Flex 10-10.