The necessity for a fly control program for beef herds is inevitable and if you haven’t started a program in your herd, now is the time. 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. The horn fly alone is estimated to cause animal losses to the US beef industry of $700 million. Tests 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 yearling steers may be reduced 12 to 14 percent, 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, which is about one-half the size of a house 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. They are normally found on the animal’s back, but may migrate to the sides and the belly as the temperatures increase. They are weak fliers, but may be carried great distances by high winds. The females leave the animal only to lay eggs in fresh cow manure, where they hatch into larvae. The life cycle is complete in eight to forty-five days depending on temperature and humidity. The best methods of fly control are the integrated approach, using several different methods and insecticides for a longer lasting, more effective fly control program.

Pour-Ons, Ear Tags, Spray Formulations, and Dusts are the traditional methods of fly control. Feed-through fly control has become an increasingly popular method of fly control. These additives generally fall into one of two categories: insect growth regulators (IGR), or larvicides. IGR’s like Altosid and Dipteracide interfere with the larvae development and are species specific, thus targeting only a single fly species. Larvicides like Clarifly and Rabon prevent flies from breeding and are not species specific, thereby controlling face flies and horn flies.

An important consideration in the use of these products is the availability of other untreated cattle in the proximity. If there are many neighbors (within 1-5 miles) with cattle who do not use these control products producers often see little benefit from feed-through control in their mineral treatment for flies.

When making decisions about fly control it is important to realize that there are many effective programs. Producers should develop a program for their operation that is cost effective and most convenient. Some of the factors to consider when developing a fly control program for a herd include:

• Young cattle should receive more attention than older cattle. They are still growing and flies can decrease gain, which affects income directly.
• Young cattle are much more susceptible to pinkeye.
• Fly tags are convenient but have some drawbacks.
• Full season control from fly tags, especially for face flies, is generally not possible. 3 to 4 months of control is average for fly tags. Flies can be an issue for 6 to 7 months depending on weather conditions.
• Flies can develop resistance to products used in fly tags. Be sure to rotate tags based on the insecticide ingredient and at the end of fly season remove the tags.
• The use of two fly tags (one in each ear) extends control by only 10-14 days in most areas.
• Dustbags, oilers, face mops and other “self medicators” can be very effective because they provide for long-term high concentrations of insecticides on cattle.
• Locations for “self-medicators” must be carefully chosen so that cattle will get frequent contact.
• Rotating pastures can help reduce fly populations as flies are attracted to manure and routine hang out spots.

There is not one stand-alone method that will control flies for the entire season. Certainly using one method is better than none, but a combination with strategic timing is usually the best route. Talk with your Extension Agent about what might work best for you in your cattle operation.

Products for control of Horn Flies and Face Flies.

Pour-Ons
5 Pyrethroids (1-10% Concentrations)
1 OP (7.6%)
2 Endectocides with claims for flies

Ear Tags
8 Pyrethroids
5 OP’s (5-40%)
2 combo OP & Pyrethroids

Spray Formulations
4 Pyrethroids (10-42.5%)
6 OP’s (5.8-50%) 2 OP’s (1-50%)

Dusts
1 Pyrethroid (3%)