Horse Flies

(News article for May 28, 2020)

Have horse flies been driving you crazy recently? I received a few calls this week from residents inquiring about horse flies and what they can do about them. We are not even done with the onslaught of buffalo gnats and now horse flies are eating people alive. There is not much you can do to reduce the population of horse flies in your area, but there are some repellents you can utilize that may make your life easier.

Horse flies and deer flies are both in the insect family Tabanidae and are serious pests to cattle, horses, and humans. They become active when the weather gets warm and continue to persist throughout the summer and into fall. The adult life span is 30-60 days and the females must consume a blood meal to produce fertile eggs. One female will lay 100-1000 eggs per year. The male flies do not bite.

Female horse flies lay their eggs on leaves, twigs, and rocks. They prefer aquatic vegetation and populations are higher in wet and wooded areas. Females are attracted to movement and carbon dioxide. They will lay and wait in shaded areas for host to walk by, then inflict a painful bite and have their blood meal. Some people are allergic to horse fly bites and may experience some pain, itching, and swelling.

Repellents containing DEET, citronella, or geraniol are effective against horse flies. Using a repellent along with wearing long sleeves and long pants is the most effective way to prevent horse fly bites when you spend time outside. Look in the camping section of your local store for a clothes treatment containing permethrin that will repel horse flies, ticks, mosquitoes, and other insect pests. Permethrin clothes treatments are supposed to last through multiple washes. Livestock will benefit from a pyrethroid insecticide pour on, ear tags, or collars.

The flies are most active just before sunrise and three hours after sunrise. Another peak in activity is two hours before sunset and just after sunset. Timing your activities around those active periods may provide a little relief, but those are also the coolest times of the day when most people enjoy being outside.

Horse flies and deer flies are native to North America and find our mild climate and wooded, wet areas desirable. They are not going to go away but using repellents will make your outdoor activities more enjoyable. Good luck!


Squitier, J. M. (1998, February). Deer Flies, Yellow Flies, & Horse Flies. Retrieved May 5, 2020, from

Jessie Hoover is a County Agent with the LSU AgCenter covering horticulture in East Feliciana, West Feliciana, St. Helena, and Tangipahoa parishes. For more information on these or related topics contact Jessie at 225-683-3101 or visit

Horse fly

American horse fly (Photo by: Sturgis McKeever, Georgia Southern University,

8/12/2020 9:07:40 PM
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