CONTROL HORN FLIES
Recent rains have brought about the need for a fly control program. The two major species of flies that cause the most serious decreases in beef production and require the most control efforts are the horn fly and face fly. Test have shown that the annoyance, irritation and blood loss caused by flies can reduce weaning weights of calves nursing fly infested mother cows by 12 to 14 pounds; average daily gain of grazing yearly steers may be reduced 12 to 14 %, or as much as 30 pounds during the grazing season. Both face flies and horn flies annoy cattle, resulting in reduced grazing time and increased energy expenditure.
The adult horn fly has piercing/sucking mouth parts and feeds on blood and tissue fluids of cattle. They spend most of their adult life on cattle and feed 20 to 40 times a day. The fact that adult horn flies spend most of their time on cattle makes their control much easier.
The face fly is about the size of a house fly. They are non-biting and feed on secretions from the eyes and muzzle. When feeding around the eyes, they cause irritation creating an environment suited to bacterial growth. As the eye becomes irritated and begins to weep, it attracts more and more flies, adding to the irritation and opportunity for spread of infection.
Other flies common to cattle are the house fly, which feeds on organic matter, and the stable fly, which feeds on blood.
Cattle can tolerate low horn fly populations. When horn fly populations reach 100 to 200 per animal it is economically advantageous to begin a control program. There are several methods of fly control, such as insecticide sprays, dusts, pour-ons, oilers, dust bags, ear tags, oral larvicides in minerals and blocks and controlled release boluses.
In an integrated fly control program two or more products that compliment each other are used. Many cases have been reported where flies developed resistance to insecticides that were very effective when first introduced. A good example are the organophosphate and pyrethroid ear tags that were very effective when first introduced several years ago.
To combat this development of resistance to insecticides a producer should consider using another method of fly control, such as sprays, dusts, pour-ons, oral larvicides, etc. in the early part of the fly season, then putting slow release insecticide ear tag (containing a different family of insecticides than in the products used earlier), in later (early June). This will extend the effectiveness of the ear tags further into the fall.
Another fly control management practice that should be implemented is to cut out old ear tags in the fall to eliminate the chance of flies being exposed to sub-lethal dosage of insecticides and developing resistance.
Most producers seem to be familiar with the use of sprays, dusts, pour-ons, ear tags, and self applicating devices. The sprays, dusts and pour-ons only give effective control for a specified period of time after application. Self application devices should be located where cattle are forced to go through to obtain water or salt to insure daily usage. Dust applicators should be protected from rain to avoid caking. The pour-on systemic insecticides are effective for a period of time on flies that feed on blood. Another means of fly control is oral larvicides which may be obtained in several different carriers, such as free choice minerals, blocks, etc. These products, when fed, pass through the digestive tract of the animal and kill developing fly larvae in the manure or inhibit their development. They are not effective against adult flies and, for this reason, if cattle not receiving an oral larvicide are located close to your herd, you may still have fly problems.
Another type of fly control is the controlled release bolus. The bolus settles into the reticulum where a controlled dose of chemical is released in the manure. It is an insect growth regulator and prevents the immature insects from becoming adults. Similar to oral larvicides, if a nearby herd does not use the oral larvicide or controlled release bolus, you may still experience fly problems.
The best method of fly control is the integrated approach, using several different methods and insecticides for a longer lasting, more effective fly control program.
