The face fly, Musca autumnalis, is a robust fly that superficially resembles the house fly. It is a nonbiting fly that feeds on animal secretions, nectar and dung liquids.
Adult female face flies (the most damaging of the two sexes) typically cluster around the animals’ eyes, mouth and muzzle, causing extreme annoyance. Their activity around the animals’ eyes allows face flies to serve as vectors of the bacterium that causes pinkeye and for parasites such as Thelazia eyeworms.
Female face flies are also facultative blood feeders, meaning that they gather around wounds caused by mechanical damage or biting-fly activity to feed on blood and other exudates.
Face flies are monitored by counting flies on the faces of 15 pastured animals; average counts in excess of 10 flies per face are considered economically injurious.
Face flies and another economically damaging fly, the horn fly, breed exclusively in very fresh manure pats on pasture. As a result, cultural controls such as manure-management practices in and around barn areas that are highly effective against house and stable flies will have no impact on horn and face fly populations.
Insecticidal control options for horn and face flies include whole-animal sprays, self-application devices, feed-through oral larvicides and controlled-release devices, such as ear tags and tapes.
Whole-animal sprays provide rapid relief from fly pressure. Animal sprays are applied either as a dilute coarse spray, often under high pressure to soak down to the skin, or as a fine low-volume, more concentrated mist.
Self-applicating devices include back rubbers covered with an absorbent material treated with an insecticide-oil solution or dust bags filled with an insecticidal dust. Back rubbers and dust bags should be placed in gateways, near water and feed sources, and in other areas where the heads of animals make frequent contact with them.
Feed-throughs include insecticidal feed additives, treated mineral blocks and bolus formulations. These treatments are generally less effective for face flies than for horn flies. In either case, feed additives have no effect on adult flies that are already present or that may immigrate from neighboring farms.
Unless your farm is very isolated or you are participating in an area-wide management program, feed-throughs alone may not provide satisfactory fly suppression.
Controlled-release ear tags and tapes are generally very effective for horn fly control in many parts of the country, and they often reduce face fly pressure as well.
You can prevent face flies from becoming a serious problem by following these guidelines:
- Do not treat unless face flies exceed threshold levels (10 flies per animal).
- For the best face fly control, use ear tags containing a pyrethroid insecticide such as beta-cyfluthrin or zeta-cypermethrin. These insecticides do a good job of repelling face flies.
- Remove ear tags in the fall to reduce development of resistance to low levels of pyrethroids.