April 13, 2021

Beware of buffalo gnats

I was talking with a person who called in yesterday to ask a question about her chickens. As we were discussing her situation, she brought up the situation we had in the state several years ago about the infestation of buffalo gnats. So, about five years ago, I was contacted by a number of small flock poultry producers who said they lost like 20 birds or so overnight. As I remember, the cause of the mortality was a heavy infestation of what are called buffalo gnats.

These small flies or gnats congregated around the chickens and actually bit the birds and localized in the trachea of some of them and caused them to suffocate. It was May and the weather had turned warm with a lot of rain occurring. As I investigated the situation and discussed what was happening to a number of producer’s small flocks, it became apparent that the problem was these black flies, or buffalo bnats as they are called.

Dr. Yvette Johnson, a poultry veterinarian at the University of Illinois, and I tried to find out how these gnats could be controlled and how we could advise poultry producers on what kind of treatment they could use to prevent this from happening. Therefore, we came up with an article on this issue, with some questions and answers.

What are they?

Buffalo gnats or black flies are blood-sucking flies of the Simuliidae family. The females may attack people and animals in an effort to have a blood meal for egg production.

Do they pose a public health risk?

In humans, their bites typically cause pain, itching, and swelling. However, those who have an allergic reaction may have more serious complications.

Will they harm my animals?

The consequences for animals can be more severe. Livestock and poultry are sometimes killed by the flies when bitten by large numbers of them. Death can be due to anaphylactic shock, toxemia, blood loss, or suffocation when the flies are inhaled. Some species of black flies can transmit a blood-borne parasite that affects poultry, called leukocytozoon.

When can I expect them to be a problem?

The adults emerge in the late spring to early summer and are known to travel more than 10 miles in search of a meal. The larvae are very sensitive to water temperature. Once the water temperature reaches 66 - 75 degrees F the larvae will die and the buffalo gnat season is over until next year.

Why are they causing problems now?

The eggs are laid in running water and the larvae are filter feeders. They are sensitive to sediment, toxins, and low oxygen levels in the water. With adequate rainfall and as surface water quality improves, the conditions are more favorable for the flies.

How can I protect myself from them?

Black flies are outdoor, daytime feeders, so the best protection is avoidance. If you must be outside, light colors and long sleeves are recommended. Permethrin-treated clothing and insect repellants containing DEET have been used with limited success.

How can I protect my animals from them?

Animals that are housed indoors are at a much lower risk of being bitten even if the building is not fly-proof. It is recommended that poultry be kept indoors in a darkened barn during the day. Usually fans or some means of cooling are needed. Permethrin-based fly control products are recommended for livestock and poultry.

Ken Koelkebeck is a University of Illinois Extension poultry specialist.