This saliva is highly irritating and can lead to varying degrees of localized tissue swelling, particularly if the bite occurred around the eyes, lips, or ears. This localized swelling may last for 1-2 weeks and produce intense itching. Large scale control of black flies is difficult. As a result, the best defense against these annoying pests is to use personal protection during the time periods when the adults are active. Tucking pant legs into the socks can also prevent black flies from feeding around the ankles.
Insect repellents can provide some protection if they are applied to exposed body areas.
However, when applying insect repellents to the head area, caution should be used to avoid getting these materials into the eyes or mouth. Black flies can also be annoying to livestock and pets, particularly horses and dogs. A number of different products are available for direct application to horses that may provide some level of temporary relief. Similar products are also available for dogs. However, for dogs it may be easier to let them take shelter indoors during the day when black flies are most active.