Create a No-Fly Zone Around Cattle

By Sarah Watson, Livestock Editor
Wednesday, June 25, 2008 1:31 PM CDT

As the weather warms, flies begin their annual summer duty of annoying and attacking cattle, causing a negative economic impact on the herd. To lessen the stress on cattle, producers need to evaluate and implement sufficient and successful fly control programs.

The three most problematic pests are the horn, face and stable flies. These are the big three when it comes to annoyance and economic impact issues.

Face fly

The face fly congregates about the eyes and nose of animals, causing annoyance and possible disease transmission.

It closely resembles the house fly except it is approximately 20 percent larger and darker. Other differentiating characteristics include: 1) the abdomen of the male face fly is orange and the female has an orange stripe; the abdomen of the house fly is white or light grey and 2) the compound eyes of male face flies nearly touch but are separated in the house flies.

The persistence and habit of congregating about the eyes and nose of animals helps distinguish the face fly from the house fly in the field. House flies may congregate on the faces of cattle in confined feedlots or dairy pens. Face flies are pasture flies and are not found in feedlots.

The economic impact face flies create is their significant annoyance to the animal and disease transmission. Face flies are the primary transmission vector associated with the bacteria Moraxella bovis that causes pinkeye. If pinkeye isn’t bad enough, face flies have also been linked to transmitting brucella abortus (the contributing agent of brucellosis) and Bovine herpes virus-1 (the contributing agent of IBR).

Pinkeye can results in market price per pound discounts, but also the reduction in weaning weights of 15-20 pounds when sight in one eye is lost or as much as 60 pounds when sight in both eyes is lost, according to Dr. Ron Lemenager, professor of animal science at Purdue University.

Face flies lay their eggs in fresh manure and move from animal to animal in the pasture, but are not typically found in feedlot environments.

Horn and Stable Flies

Horn flies are about half the size of the house fly, while stable flies are similar in size to the house fly. Both horn flies and stable flies are hide piercing, blood sucking flies.

Favored by warm, moist weather, horn flies emerge in spring and seek cattle and other host animals. Although they locate hosts most successfully during the day, they usually disperse at night, sometimes traveling as far as five miles.

Horn flies stay on cattle most of the time and cluster on the backs, shoulders, sides and belly of pasture cattle. They feed 20-30 times per day and only leave the animal long enough to lay their eggs in fresh manure.

Soon after initial feeding, females periodically leave the host animal and deposit 1 to 14 eggs in fresh cow manure. Both male and female horn flies apparently feed on the manure from time to time. Eggs hatch between 16 to 24 hours later.

The stress due to annoyance and blood loss can result in lighter weaning weights and greater weight loss in lactating cows.

Horn flies have also been implicated in transmitting mastitis in non-lactating cows. The economic threshold for horn flies has been reported at between 50-100 flies per side.

Stable flies usually attack cattle when they are in the shade and stay on the animal only long enough to obtain a meal and then seek shade on a fence, barn wall, feed bunk or vegetation to digest it.

They lay their eggs in spoiled or fermenting organic material mixed with manure and dirt typically found in feedlots, as well as around bale feeders, feed bunks, and hay stacks. Depressions in weight gains of over 0.4 pounds per day and reductions in milk production of 30-40 percent have been reported.

Control

Sanitation is the first step in creating a no-fly zone for cattle, but to be successful in controlling flies it is important that producers implement a control program that best compliments operation. Reliance on a single practice is not the best approach to achieving effective and economical pest control.

A better approach is to combine routine sanitation with a variety of pesticide strategies such as baits, residual sprays, space sprays, and larvicides whenever flies are a problem.

Insecticides, such as sprays and larvicides, should be reserved for treatment of fly breeding areas not eliminated by normal sanitation procedures.

Feed-through larvicides in supplements are less than effective in controlling horse flies and stable flies because they often breed in non-manure areas.

Flies on pasture cattle can be controlled when cattle are forced to use dust bags or back rubbers. The key to their success is having them properly located and in working order during the entire fly season. Regular spraying can also control flies when done at two to three week intervals. Sprays tend to be much more effective in controlling horn flies than face flies.

Insecticide pour-ons can also provide effective fly control when applied along the top-line, over the poll and down the face. Control of face flies and horn flies on pastured cattle can also be achieved with insecticide impregnated ear tags. These ear tags are not effective in controlling face flies or house flies in and around barns or confined feeding areas.

There are two main classes of insecticides used in ear tags n pyrethroids and organophosphates. Ear tags containing pyrethroids provide excellent control of both face and horn flies, however, horn fly resistance has developed in recent years.

The organophosphate tags are effective against pyrethroid resistant horn flies, but they are not as effective as pyrethroid tags against face flies.

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