Flies are a well known and common pest to most all classes of livestock. With heat and humidity, flies thrive and this makes summer in the Ozarks a prime environment for fly populations. Economic losses can be substantial, particularly in beef and dairy cattle. In cattle, flies can cause production losses in the way of reduced weight gain, lowered milk production and the transmission of disease.
There are a few primary species that create the biggest problems to cattle producers.
Horn flies are the most economically significant. These are small, dark colored flies that live their entire adult lives on cattle primarily over the back, shoulders and belly. Eggs are laid in fresh manure and develop into adult flies in about 10 to 12 days. Adults feed on the blood of the animal and are capable of transmitting blood-borne diseases such as anaplasmosis and bovine leucosis. Blood loss and annoyance/irritation result in reduced weight gains in growing cattle and reduced milk production in cows.
Face flies are another significant external parasite of cattle. Face flies resemble house flies but are slightly larger and are found primarily around the head of cattle where they feed on secretions from the eyes and nostrils. Face flies, like horn flies, lay eggs in fresh manure. Face flies can cause significant annoyance to cattle and may disrupt normal grazing, thereby affecting production. Likely the most destructive role of the face fly is the transmission of the causative agent of pinkeye from one animal to another.
House flies are a common pest and exert their negative impact on production primarily through annoyance and potentially disease transmission. House flies reproduce in manure as well as decaying organic matter.
Numerous methods for control of fly populations exist. Unfortunately, flies are challenging to control and resistance to certain classes of compounds is well documented. The most effective control protocols involve a multimodal approach and rotation of insecticide classes. Producers should thoughtfully choose insecticides based on the class of the active ingredients and plan a rotation schedule that changes insecticide class every 1 to 2 years. Furthermore, products should be used as recommended and underdosing (especially in regards to fly tags) should be avoided to prevent resistance remembering that dead flies do not breed resistance.
Fly tags and pour-on products are some of the most common methods used to minimize production losses due to heavy fly infestations. Additionally, sprays, backrubbers and dust bags are used when frequent application is desired. Feed through products are available that limit larval development in the manure pat and premise sprays can kill flies in the environment. Organic methods also exist such as fly predators and fly traps.
Each producer must decide what methods work best for his or her operation. Consultation with your veterinarian can help.
Dr. Darren Loula, DVM, is owner of Christian County Veterinary Service, LLC, a mobile large animal vet clinic.