All flies are alike.” If you approach fly control on your dairy with this attitude, you will never be satisfied with the results.

The truth is, all flies are different. And within those differences  —biology and habitat, for example — you will find the secret of how to control the flies that make a pest of themselves at your dairy and your neighbors.

Here are four reasons why you need to know what fly you’re dealing with before you take action.

1. Biology dictates treatment.

Each species of fly lives and breeds in different areas on your farm and has different life cycles, explains, Richard Warriner, specialty field development and technical services entomologist for Wellmark International. If you fail to take these differences into account, your treatment will more than likely fail.

For example, if you have flies biting your cows on the lower legs and you use dusts, pour-ons or insecticide ear tags, it won’t do a thing to control stable flies. But those treatments will kill horn flies. The difference lies in their biology, says Warriner. Stable flies bite and run. Horn flies bite and stay on the cow where they can get enough exposure to the treatment products to kill them.

Four primary species of flies — house fly, face fly, stable fly, and horn fly — cause the majority of problems on dairy farms. But depending on the climate, proximity to water and the management style of your dairy, there can be several more species that will pay you a visit. Those include the horse fly, deer fly, heel fly, black fly, and blow fly, to name a few. However, not all of these species of flies become pests to your cattle, explains Wes Watson, extension entomologist at North Carolina State University. For example, even though metallic-colored blow flies are common on farms, they typically do not become pests. They seek out carrion and manure for breeding, and, on occasion, will be attracted to offensive odors associated with open sores on animals.

The chart at right shows the four major fly species. You can use it to identify which flies are causing problems on your dairy, and then determine what control measures you should use.

2. Economic thresholds for treatment differ.

How many flies does it take to justify taking action? This, too, varies by species of fly, explains Jeff Tomberlin, assistant professor and extension livestock entomologist at Texas A&M University. “Certain fly species cause more harm at lower populations than other fly species,” he says.

For example, with stable flies, the economic threshold for treatment — when treatment will yield an economic return — is four flies per leg. But with house flies, the economic threshold for treatment is 100 specks on a fly card in a week. (Fly cards are 4- x 8-inch index cards posted in areas where the flies rest, and you count the specks made on the card within one week.) That’s because stable flies, which bite and suck blood from animals, bother cows, cause them to stamp their feet, shake their heads and even eat less feed. On the other hand, house flies are more of a general nuisance. They can, however, transmit some diseases, such as bacterial scours and parainfluenza, so controlling their numbers is still important.

3.Where did the fly come from?

If your neighbor calls and complains about flies from your dairy, how do you know they came from your dairy? If you have an integrated pest management program (IPM) — including sanitation, biological controls, trapping and insecticides when necessary — and flies seem to be under control at your dairy, it could be that they are from somewhere else. This is where identifying the species of fly can be important.

For example, a neighbor with a small swimming pool for the kids to play in complained about biting flies to a neighboring dairy, explains Tomberlin. However, the type of fly identified at the family’s house was the deer fly. This type of biting fly is attracted to and hangs out near sources of water, such as pools, streams, rivers and ponds. That makes it very unlikely that the flies were visiting from the dry-lot dairy next door.

Another example, says Watson, had to do with a large poultry operation. Neighbors filed a nuisance suit, saying their families could not go outside due to the large number of biting flies. Investigation revealed the flies bothering the neighbors were stable flies. However, stable flies rarely if ever breed and live in poultry manure. It turned out the origin of the stable flies was from a farm a mile down the road that stabled 10 horses, but did not have an adequate manure-management plan. Unknown to the neighbors who filed the suit against the neighboring poultry unit, stable flies can fly long distances.

Granted, when many farms reside in an area, it can be difficult to identify where the flies come from. But when you understand how the species differ, it arms you with the information you need to help explain the situation to your neighbors, and initiate an investigation to discover the type and origin of the flies bothering them.

4. Make your fly-control efforts more effective.

Once you identify the species of fly that you are dealing with, you can select the most suitable control methods — baits, traps, sprays, or biological controls agents — designed to target that pest, says, Bob Arther, manager of parasitology and entomology clinical development at Bayer Animal Health. Companies that sell pest-control products to livestock producers have specialists on staff who can help you identify the problem and find a solution. Don’t be afraid to ask for help.

Designing a control program that targets your specific pest is very important, stresses Watson. Take, for example, a producer who was using pheromone-baited jugs to trap and control house flies. These are the type of jugs that use water and a pheromone to attract house flies. When the producer started the program, he got great results. However, a few weeks later, house fly numbers at the farm had increased. An investigation revealed he had stopped using the pheromone bait to cut cost, and had started baiting the traps with raw meat. The meat spoiled and attracted an entirely different species of fly — the blow fly. So, in this case, the producer had failed to control the house flies on his farm by improper baiting.

Another concern with not knowing your target and treating anyway is the overuse of pesticides. Some species, such as horn flies, build up resistance quickly, says Tomberlin. To target the flies effectively, you must constantly change the class of insecticide used in order to get results long-term. However, there are only a few classes of insecticide available, so all must be used judiciously — and as a last line of defense.

Remember, insecticides are just one of four tools used as part of an IPM program. Your first lines of defense are sanitation, biological controls and trapping. And, depending on which fly you are dealing with, you can identify different hot spots on the premises. For example, house flies and stable flies breed in moist organic material in barns, calf hutches and around hay rings, while horn flies breed in undisturbed manure piles in pasture. The same is true with biological controls. Different species of parasitic wasps seek out different species of flies. If you buy and release a parasitic wasp that doesn’t target the correct fly species, you will be wasting money.

When it comes to fly control, one plan doesn’t fit all. For the best control, and the most cost-effective treatment, identify the flies on your farm and develop a plan that targets your specific pest.


Online resources

If you’d like to learn more about identifying flies and how to control them on your dairy, check out these resources on the Internet.

How to identify flies

Species:  House fly
Size: 6 to 9 mm long
Appearance:  Gray with four dark stripes on the back. Non-metallic. Straw-colored face. Sponging-type mouthparts.
Location: Premise flies. Stays close to housing structures.
Life cycle:  Seven to 10 days from egg, larvae, pupa, to adult. Eggs laid in moist organic material and larvae remain there until they crawl to dry area to pupate.
Controls: Traps, sanitation, baits, premise sprays.

Species: Face fly
Size: 6 to 9 mm long
Appearance: Light gray, four dark stripes on the back, straw-colored face.
Location: Pasture fly. Occasionally winters in buildings.
Life cycle: 12 to 20 days from egg, larvae, pupa to adult. Eggs laid in fresh manure. Larvae develop in manure, pupate in soil. Adults feed on mucous secretions around eyes, nose and mouth.
Controls: On-animal products, such as ear tags.

Species: Stable fly
Size: 5 to 6 mm long
Appearance: Gray with black spots on back and abdomen. Four dark stripes on back. Has piercing mouthpart.
Location: Premise and pasture fly. Found mainly on animal’s legs in housing, feedlots, pastures, and especially around hay rings.
Life cycle: 24 days from egg, larvae, pupa to adult. Eggs laid in semi-moist organic media. Larvae crawl to drier areas bury selves to pupate. Adults feed on blood, tend to bite and run.
Controls: Sanitation. Remove suitable breeding material. Premise sprays.

Species: Horn fly
Size: 4 to 5 mm long
Appearance: Dark gray with piercing mouthparts.
Location: Pasture fly. Spends most of its time on host animal’s body.
Life cycle: 10 to 14 days from egg, larvae, pupa to adult. Eggs only laid on a fresh manure pile. Larvae develop in manure, pupate in manure or in soil. Adults feed on blood, spend majority of time on host.
Controls: Clip and drag pastures. Feed additives, on-animal products, such as ear tags, dusts, pour-ons.