Shoo, fly: Proper fly control will increase profits

Special to The Post

Insects will fly away with some of your profit if you don't control their numbers. Several species of flies often carry and transmit disease organisms that can affect humans as well as animals. In addition, flies can cause animal stress, weight loss, reduced feed efficiency and decreased milk production.

"Integrated pest management is the least expensive way to control flies," said Sonja Swiger, Texas AgriLife Extension entomologist at Stephenville. "Integrated pest management involves a combination of biological, cultural and chemical control methods. The benefits offered by integrated pest management, in addition to its economics are the utilization of nature through predators, requirement for sanitation and prevention of fly resistance to insecticides."

Types of flies

Swiger, a frequent speaker at extension meetings in Franklin, shares information about horn, house and stable flies.

The horn fly is the number one pest that affects cattle. Their populations peak in early summer and decrease when the weather turns hot and dry. Horn fly numbers increase again in the fall with occurrence of rainfall and lower temperatures.

Horn flies are no longer a major problem after September or October.

The life cycle of the horn fly begins when the adult female laying eggs in cow manure. It takes 10 to 20 days for an adult to develop from an egg. Life cycle stages for all flies include egg, larvae or maggot, pupae and adult. The horn fly adult lives for up to three weeks.

Both sexes live on a cow and feed on the animal's blood 20 to 30 times per day. One fly will consume approximately 10 micro liters of blood per day, and it is not uncommon for 3,000 flies to reside on one cow. This number of flies will consume a total daily blood amount of 30 milliliters, which is slightly more than one fluid ounce.

Bites from the horn fly hurt and they leave welts on the skin.

The economic threshold for treating horn flies is 200 to 250 per cow. Horn fly populations at or above the economic threshold can cause 15 percent to 50 percent less weight gain.

House flies do not bite, but they can be very annoying to people with their constant flight and landing habits. They irritate animals while feeding on mucous around their nostrils. House flies can harbor and spread more than 200 disease organisms and, as a result, they threaten the health of animals and humans.

House flies steal profits from cattlemen by increasing disease incidents in the herd, resulting in greater medicine and veterinary service costs and reduced animal performance.

Female house flies lay 50 to 100 eggs at a time and approximately 500 in their lifetime. Adults develop from eggs within 10 days and live up to three weeks while feeding on moist organic matter such as manure, rotting hay, silage, feed or garbage. Their flight range is about seven miles.

Stable flies and house flies look similar, but their mouth parts are different. Stable flies have protruding mouth parts that allow them to cut skin and draw blood. Their bites are painful to animals and people, leaving open wounds.

Stable flies are more abundant in animal confinement areas. Both sexes feed once per day and stay on animals for only a few minutes. They move to walls, fences or other surfaces to digest their meal. Stable flies attack many areas on an animal, but primarily the legs.

The stable fly completes its life cycle in three to four weeks. Females lay several batches of 40 to 80 eggs for a total of approximately 500 to 600 during their lifetime. They lay eggs in wet straw or decomposing vegetation mixed with urine or feces. Economic threshold treatment level is two to four flies per leg.

Control methods

"Commercially available parasitic wasps are used in biological control of house and stable flies," said Lee Townsend, Extension entomologist with the University of Kentucky. "Parasitic wasps insert their eggs into several species of fly eggs, maggots, or pupae. The wasp completes its development, emerges as an adult and continues its life cycle by searching out more hosts. These small wasps only attack flies and don't sting or bite other insects, animals, or humans. Parasitic wasps haven't been proven effective on pasture fly pests such as horn flies.

"It is generally recommended that parasitic wasps be released periodically before and during fly season. The number of parasitic wasps released usually depends upon the number of livestock present. Usually, the company provides a formula or guidelines to calculate the number of wasps to use. Continued releases are needed to keep large numbers of wasps available throughout the summer."

"Several species of parasitic wasps are available," Townsend said. "These species may be identified by their scientific names in advertisements or brochures. The small amount of research data available from the Midwest indicates that Spalangia nigroaenea is the commercially available parasite that is most likely to attack both house and stable fly pupae in feedlots. Muscidifurax zaraptor will provide some parasitism of house flies. Spalangia nigra, Spalangia cameroni, and Spalangia endius will provide some parasitism of stable flies.

"Producers should not buy unspecified blends of species or shipments of Nasonia vitirpennis. Field trials have shown that N. vitripennis is not effective in Midwest feed lots," Townsend said.

"Cultural control of horn and stable flies involves the removal and spreading of fresh manure from barns and stalls," Swiger said.. "Design stalls for good drainage and for complete manure removal capabilities. Once manure is removed from barns and stalls, it is best to spread it on pastures or crops to facilitate faster drying. General sanitation practices greatly enhance fly control.

"Damp hay bales during the winter are ideal breeding sites for stable flies, so keep hay dry during storage and feeding. Clean wet feed from troughs weekly and dispose of in a manner to prohibit access from flies. Exposed organic matter disposal is critical for house fly control. Fly strips work for small populations of stable flies, but are more effective in house fly control. Light traps control house flies, if the traps are cleaned regularly," Swiger said.

Chemical control

Swiger listed several chemical fly control methods during a presentation in Franklin, and first discussed insecticide-treated ear tags. She recommended alternating uses of ear tags between those containing an organophosphate and ones containing a pyrethroid to help avoid development of chemical resistant flies.

Trade name examples for ear tags containing organophosphate are Patriot, Warrior, Terminator II and Optimizer. Pyrethroid containing ear tags are sold under product names such as Gardstar Plus, CyGuard, Saber Extra, XP 820 and Python. There are also ear tags available that contain avermectin and Avenger with endosulfan.

"Don't use ear tags before 100 flies are counted per cow," Swiger said. "Cattle should be tagged in March or later to minimize early-season fly resistance. More effective fly control occurs later in the year. Read product labels carefully and remove tags when recommended. Leaving tags in ears all year increases resistance chances. Rotate insecticide classes or active ingredient from year to year. Do not use ear tags impregnated with a combination of organophosphate and pyrethroid insecticides."

Cattle often are sprayed for flies during seasonal round-ups, although livestock sprays are not long-lasting. Residual wall sprays are effective for stable and house fly control and available products include Demon, Cislin 10 and Dyfly Plus. A common method for controlling flies on cattle is backrubs. However, they are not effective on stable flies because they do not treat the legs of cattle, only their backs. Products available for use in backrubs are CoRal and Atroban.

"Feed additives containing insecticides kill fly larvae by passing through a cow's digestive system into the manure," Swiger said. "An advantage of feed additives is that they can be used for free-range and confined cattle. A disadvantage is the difficulty in regulating a cow's feed intake. Some animals will eat more insecticide than they need and some will not get enough.

"Boluses, used for fly control are large pills containing insecticide. The boluses are retained in the cow's second stomach or reticulum. They dissolve slowly continuously releasing insecticide."

Fly baits offer a convenient way to control house flies. Baits are made with sugar containing materials coated or impregnated with insecticides. Adult flies are attracted to the bait and are controlled by the insecticide as they eat the sugary substance. Two commonly used baits are QuickBayt and Golden Malrin.

QuickBayt is a ready-to-use dry scatter bait and is a combination of imidacloprid insecticide and muscalure, a house fly sex pheromone. Use rate of this bait is six ounces per 1,000 square feet of area. A disadvantage of QuickBayt is that it cannot be applied around animals.

Golden Malrin is a combination of methomyl insecticide and muscalure. It, too, cannot be used in areas where animals are present and must be applied outside of animal facilities. The use rate is eight ounces per 1,000 square feet.

Successful fly control programs result from identifying the species and determining if the population size is at or above its economic threshold. The most effective and economical control will result from the use of Integrated pest management. If an insecticide is required, read and study the product label before application.

* Robert Fears is a freelance writer and ranch management consultant.