Shoo, Fly!
Flies are more than an annoyance; they could be costing you dollars in lost performance and disease.
Swat! You may have gotten that one, or just left a handprint on your arm where you swatted and missed. As annoying as flies can be to humans, livestock have to live in the insects' breeding and feeding grounds. The pests could be spreading disease, causing losses in milk and feed efficiency, annoying cattle to the point they quit eating, and ultimately decreasing your bottom line. While there is no 100% sure-fire way to get rid of flies, there are steps you can take to reduce their impact on your herd.
Different types of flies feed on different types of hosts and organisms. The Hessian fly, for example, is considered one of the most destructive pests of wheat in the Midwest. Livestock producers, however, tend to focus on houseflies, stable flies, horn flies and face flies — each of which provides a different challenge to eradication and control.
The first step to going on the offensive with flies is to understand their feeding habits and breeding grounds, then go on the defensive with controls.
House and stable flies
The housefly is a general nuisance to basically anything that lives on land. It is also a potential mechanical vector of diseases and pathogens. The housefly can spread these things through its feces, regurgitation and microbes that attach to the fly as it moves. Houseflies can develop in as few as eight days, but development usually takes 10-14 days. Their oviposition sites, where the metamorphosis occurs, are in all animal manure — fresh or aged, garbage and any other decaying plant or animal material.
The stable fly is similar in size to a housefly, but much more damaging to the livestock industry. These flies will mainly prey upon cattle, swine, horses, sheep, goats and dogs. While the housefly regurgitates its food to break it down, then consumes it, the stable fly has a piercing mouthpart that it uses to bite its host. These bites can be painful to the animal, causing an annoyance, blood loss and possibly the spread of disease.
"It is estimated that stable flies cause $2.03 billion per year losses to farmers and ranchers — in both pastured and feedlot cattle — in the U.S.," says Kansas State University (K-State) entomologist Ludek Zurek. "This includes direct losses due to stable fly biting, leading to cattle bunching, overheating, lower feed intake and lower weight gain, as well as indirect losses such as costs of insecticides and the labor costs to apply insecticides."
Another large difference between the stable fly and housefly is where they lay their eggs. While houseflies will lay their eggs in fresh or aged manure, the stable fly will lay eggs in aged manure and manure- and urine-contaminated hay. They will also lay eggs in compost piles and spilled feeds.
Stable flies also have a much broader range of infestation than houseflies, sometimes going many miles to find a suitable host.
Horn and face flies
The horn fly is another fly that has a piercing mouthpart, and while smaller than both the house and stable flies, horn flies are still just as annoying to cattle. The horn fly primarily feeds upon cattle, but it will also feed on horses, sheep and goats.
Upon finding a host, horn flies will remain on the host and others within the same herd for life. Males will feed up to 20 times per day, while females can feed 40 times per day. This feeding causes irritation.
"The horn fly can cause a 12- to 20-pound (lb.) weight loss difference over a summer," Lee Townsend, University of Kentucky (UK) entomologist, says. "That's probably the best way to look at it, and compare the cost per animal of not using any fly preventative measures."
The horn fly deposits its eggs inside very fresh manure, where the larva feed on the decomposing feces. Once emerged, horn flies are very strong fliers, traveling up to three miles to find cattle or other suitable hosts.
Face flies are closely related to the housefly, and even digest their food similarly. The difference is that the face fly has tiny "teeth" that they use to irritate eye tissue to stimulate tear production. The face fly will then feed off the nutrients, mainly protein, in the tear.
According to a K-State entomology release, 70%-95% of the face flies on an animal are females, due to their increased need for protein.
"Off the host, they rest on vegetation or structures at night and most of the daylight hours," Zurek says. "They feed on plant sugars and juices. On host animals, they obtain protein from nasal mucus, saliva and tears. Opportunistically, they are attracted to, and feed on, blood made available by horse fly bites or other wounds."
While there isn't much information on direct economical losses caused by face flies, there are performance losses due to the spread of Moraxella bovis, the bacteria that causes pinkeye.
Control methods
Knowing how each type of fly feeds, rests and reproduces is a major step in the right direction to stop them from annoying cattle. While it may be impossible to completely eliminate flies from a farm, ranch or pasture, control methods can reduce the number of flies "bugging" your cattle.
There are two main types of controls — chemical and physical. Chemical controls would be items such as insecticide sprays and dust bags that provide an irritant or kill the fly upon impact. Physical controls deal more with controlling or removing breeding grounds or habitats.
Townsend says what type of control producers use will differ with their type of management. "If you are in a rotating pasture system, I would suggest using a fly ear tag," he says. "It easily moves with the animal. While it works best with preventing horn flies, it will also help with face flies.
Other controls that are a little more permanent would be things like dust bags and cattle rubs. "If you use these fairly permanent set ups, place it where the animal passes several times per day to get water and mineral," Townsend says. "Ideally, place it so the animal has to hit it and raise it just a little, and it's best if they have face flaps. The rubs are easier to cover the back and neck. The flaps will ensure that the face is brushed, too, to get those horn flies off that like to spend a lot of time on the animals."
But what works for one type of fly will not work for all.
"One thing that makes stable flies hard to control is that they feed around the legs of cattle, usually within 3 feet of the ground," Zurek says. "So dust bags will not knock them off, and the morning dew will wash off most sprays."
That is why he suggests proper upkeep of your grounds and removing as many fly habitats as possible. For cattle on pasture, Zurek says there isn't too much that can be done. If producers have to supplement hay to their pastures, he suggests raking the hay and spreading the manure thin over a larger area to remove the prime breeding and developmental area of the stable fly.
For cattle in a feedlot setting, Zurek suggests keeping the pens as clean as possible. "Remove the aged and older manure as frequently as possible to remove their primary habitat," he says. "Another thing you can do in the feedlot setting is to use insecticides on outer walls of feedbunks and fences. This will help with both stable and houseflies. For house flies you can also set out some baits and traps, but since stable flies feed on blood, they will not be attracted to these."
Both Zurek and Townsend advise that another resource in your fight against flies would be your local Extension agent. He or she will be able to provide you with information on what flies are more prevalent in your area, recent university publications and contacts, and other useful resources.