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Added July 18, 2011. Several fly pests attack cattle while they are out on pasture especially horn, face, stable, horse and deer flies. Each has distinctive habits, life histories, and management options.
HORN, FACE, AND STABLE FLIES
Biology and Importance
Horn fly: The adult horn fly, Haematobia irritans, is about half the size of a house fly or stable fly. Both males and females have piercing mouthparts which they use to penetrate animal skin to obtain blood meals. Horn flies take blood meals intermittently 20 or more times each day.
The flies normally congregate on the shoulders, backs, and sides of the animals but move to the underside of the belly during very hot or rainy weather. Horn fly adults tend to align their bodies in the same direction with their wing tips facing up while resting on animals.
Unlike other flies, horn flies remain on the animals almostconstantly leaving only briefly to lay eggs on very fresh (less than 10-minute old) droppings. Development from egg to adult is completed in 10 to 20 days. The average life span is 30 days depending on the temperature. The flies overwinter as pupae in or under dung pats. Adults are strong fliers and can travel many miles.
This serious pest of pastured cattle causes reduced milk production, poor weight gain, blood loss, animal annoyance and fatigue. The weight of calves plagued by horn flies is often reduced by 12 to 20 pounds over a summer.
Face fly: The face fly, Musca autumnalis, is a
robust fly that superficially resembles the house fly. It is a non-biting fly that feeds on animal secretions, nectar, and dung liquids. Female adult face flies typically cluster around the eyes, mouth, and muzzle of dairy cattle, causing extreme annoyance. As they move from the eyes of one animal to the next, they serve as vectors of eye diseases and parasites such as pinkeye and Thelazia eyeworms. They also gather around wounds to feed on blood and other exudates. Face flies avoid shady areas.
Bottom: Life stages of the face fly.
By contrast, male face flies feed only on nectar and dung. They spend much of their time resting on branches and fences and attempting to catch and copulate with female flies as they move about. Eggs are laid on very fresh droppings and take about 2 to 3 weeks to develop from egg to adult. Adults live an average of 28 days, depending on temperature. Pupal casings are very hard making it difficult for parasitoids to penetrate.
Face flies are strong fliers that can travel miles to find animals. Unlike house flies, face flies do not enter darkened barns or stables during the summer months. Cows are attracted to shade, so offering shelter from the sun can reduce the incidence and ease the distress caused by face flies. In the fall, however, face flies enter buildings and overwinter as adults indoors in a state of diapause, or hibernation.
Monitoring and Assessment:
Horn flies and face flies breed exclusively in very fresh droppings in pastures not in decomposing materials like house and stables flies. As a result, cultural controls such as manure management in and around barn areas that are highly effective against house flies and stable flies will have no impact on horn fly and face fly populations. Practices that disturb fresh manure pats, such as using a chain or drag harrow in pastures, will break the life cycles of horn and face flies but also hinder the work of dung beetles and may deter animal grazing. Moving animals to fresh pasture every 3 days will provide them with unspoiled grass.
If enough natural enemies are present on the farm, they will work to disassemble the manurefilled part of the pasture. More than 125 different species of arthropods live part of their life cycle in manure pats in pastures when pesticides are absent, and only three of these are considered pests. One of the most active natural enemies are scarab or dung beetles.
Biological control against horn and face flies is limited to beneficial organisms occurring naturally in the field, especially those spending part of their life in cow dung. Face flies have very hard pupal casings, which many parasitoids cannot penetrate but they can be attacked by parasitic nematodes. Predaceous mites and beetles prey on the immature stages of both horn flies and face flies. Adult flies are attacked by yellow dung flies. Face flies are occasionally attacked by pathogenic fungi. Birds, bats, and spiders also contribute to overall reductions in flies of all types.
Dung Beetles: Horn and face flies require fresh manure to complete their life cycle, but dung beetles can dramatically reduce these pest populations by competing for the manure and depriving horn and face flies of a habitat for their larvae to develop. A single manure pat can produce 60 to 80 horn flies if left unprotected from predators. One of the most beneficial dung beetles has a habit of forming balls from dung in which they lay their eggs. These balls are rolled into tunnels the beetles have dug in the soil, away from the access of horn and face flies. Some studies indicate that healthy dung beetle populations can bury up to 90% of cow manure within a pasture in one week.
The benefits of dung beetles go well beyond reducing face and horn fly populations. Burying manure reduces runoff problems and increases nutrient availability from the manure, improves organic matter in the soil, and is a general benefit to soil health resulting in improved pasture growth. Removing manure makes more area available for grazing. In addition, dung beetle activity breaks the cycle of some internal pests of dairy cattle which are dependent on manure pats remaining undisturbed.
Under ideal conditions, dung beetle larvae will pupate in about 3 weeks and the life cycle is completed in about 6 weeks. Dry spells will reduce dung beetle activity. Even though dung beetles are thought to be capable of flying up to 10 miles in search of fresh dung, their populations can be improved by planning to graze animals in pasture areas where new adult beetles are expected to emerge from the soil. This effectively decreases the time beetles spend looking for fresh manure.
In some emergency cases, a farm certifier may allow the use of ivermectin for control of internal parasites, but use of this pesticide is detrimental to dung beetle populations for weeks after treatment and the NOP rules restrict the sale of milk after treatment.
To assess dung beetle activity, check the outside of manure pats for holes in the surface, or the inside for tunneling or a shredded appearance.
Poultry: When allowed to range in pastures, poultry, particularly Muscovy ducks, assist to reduce fly populations through their habit of searching for larvae in manure pats.
Face flies: Face flies do not enter darkened barns or stables during the summer months. Offering shelter can reduce face fly incidence on cows.
Horn Flies: The only effective traps mechanical controls are walk through traps that can assist in reducing horn fly populations.
Excerpt from the publication '2011 Integrated Pest Management (IPM) Guide for Organic Dairies'; reprinted with permission by the New York State Department of Ag and Markets. To download the complete booklet and find other information on IPM for organic livestock, please go to: www.nysipm.cornell.edu/organic_guide/default.asp