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 and 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 the southwest portion. Like horse flies, they have razor sharp mouths that inflict quite a bit of pain and blood spillage. Though horse flies and deer flies belong to the Tabanidae family, they are each their own species. Deer flies are in the genus Chrysops whereas horse flies are in the genus Tabanus.

Although their name suggest they feed on deer, this pest feeds on a variety of 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 yard 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, then follow the steps and recommended products throughout this easy to use DIY guide.

Identification

Before proceeding with treatment, you will need to identify and make sure you are facing a deer fly infestation and not another kind of fly. Careless identification can lead you to using the wrong or ineffective insecticides, which can be a waste of time and money. Here are some key characteristics of deer flies to know in order to learn how to differentiate them from horse flies and other type of flies.

• Deer flies are somewhat 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 and have their thorax and abdomen covered in fine hairs.
• Yellow-brown to black in coloration, have bee-like stripes on the abdomen, and dark bands on their clear wings.
• Female deer flies have large, prominent mouthparts that have have a scissor-like appearance to cut skin.
• Lay large batches of 100 to 800 eggs either in a single layer or in tiers 3 to 4 high. Eggs are cylindrical in shape and white in coloration then slightly darken to gray, brown, or black in time.
• Deer fly larvae are fairly straight and worm-like in shape with tapered ends. They have 11 to 12 segments in body, legless, and are tan, white, or brown in color. They measure between 3/4 to 1 1/2 inches in length, which is smaller than horse fly 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 through 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 in 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 and 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 body sources. In their adult form the deer fly will rest on shrubbery or tall grasses until they find a person or small to large mammal like horses, cattle, deer, dogs, or birds to feed on.

What to Look For

Deer flies only feed during the day and tend to focus on animal or people 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 animals are bitten by deer flies it can be seen with consistent tail swishing and head swishing to remove these biting flies. Once bitten, these pests can leave behind red bumps or welts. 

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

Treatment

Make sure to wear personal protective equipment (PPE) such as long-sleeve shirts, long-sleeve pants, and a hat as bites from deer flies are quite 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 or at the beginning of periods of activity. Fogging or any type of 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 throughout the day on tall grass blades or leaves when no host is available to feed on.

Keep your lawn and fields trimmed with regular mowing once the grass reaches a height of 3 inches. Adjust the mower blades on a higher setting when mowing during the summer. This will help to 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 use a pyrethroid that can be applied as fog or mist application like Flex 10-10. Flex 10-10 is a emulsifiable concentrate made to kill deer flies and other 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 effect the deer flies nervous system leading to paralysis then death.

When fogging, it would be best to wear personal protective equipment (PPE) that will protect your entire skin, eyes, and mouth. For a dependable and high volume ULV fogger, we recommend the Tomahawk TMD14 Backpack Fogger. Determine how much Flex 10-10 to use for your treatment area and sprayer by calculating the square footage of the treatment area. To do this, measure the treatment areas 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 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 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 reservoir of the sprayer with half the amount of water, add measured amount of Flex 10-10, then pour in the remaining half of water. Secure the lid to the tank and shake to ensure even agitation. Pump the primer bulb between 3 to 5 times then adjust the engines choke position to UP and move the throttle into the ON position. Pull the engines cord until it starts then once it does move the engines 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, and the area has been thoroughly ventilated and sprays have dried. When used in dairy barns or facilities: Close milk bulk tank lids to prevent contamination from spray and from dead or falling insects. Remove or cover milking utensils before application. Wash teats of animals before milking.

Prevention

After the deer fly infestation has been eliminated, you will need to 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. Keep the following preventative practices in mind to ensure deer flies do not return to your yard.

• Eliminate weeds with appropriate herbicides and mow when turf exceeds a height of 3 inches to eliminate hiding places for adult deer flies. Prune overgrown foliage and shrubbery near your home and barn as this could be used as resting sites for this pest as well.
• 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 getting rid of future generations.
• Limit moisture in your yard by covering muddy areas and holes in turf with dirt or other organic material until dry and filled. Level the land if it is creating gaps or holes for water to gather.
• 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.
• Limit moisture areas needed for deer fly larvae by removing ponds, water bodies, or other swampy areas in or nearby your home and barn. 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 prior to 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 in 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 a height of 3 inches 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 cause of flooding, building sheltered areas that provide shade for animals, and continual applications of Flex 10-10.