Author’s note: The instructions for use of the recommended insecticides are not as comprehensive as the pesticide labels and are intended to be used as guidelines only. Before using any pesticide, read the label for more specific instructions. Many insecticides are sold under brand names not listed in this publication. House fly and stable fly control on dairy farms

House flies and stable flies are the two primary fly species associated with dairy buildings. Successful house fly and stable fly control can only be accomplished by instituting an integrated fly control program. This type of program utilizes a variety of fly control methods based on a knowledge of pest biology and habits, proper sanitation and manure management and timely applications of insecticides.

Sanitation is the key to any successful fly control program since it removes fly breeding sites. Without proper sanitation, chemical control treatments will be of limited success. Manure should be removed from barns, loafing sheds and especially calf pens at least twice per week during the fly breeding season. It should be spread thinly on crop land with a flail-type manure spreader so it can dry. Manure may also be stored in lagoons or liquid manure pits; however, the liquid manure should be agitated to prevent the breeding of rat-tailed maggots.

Thorough removal of manure from corners, around posts and under feedbunks is necessary to prevent fly breeding in these areas. Rotting hay or straw, silage or other spilled feeds should also be cleaned up regularly. Leaking watering troughs and plumbing should be repaired as needed.

Residual fly sprays should be applied to fly resting areas in barns and loafing sheds to control adult flies. Insecticides applied as space sprays, mists or fogs may be used to provide rapid knockdown of adult flies but have no residual activity and will only control flies present at the time of application. Fly baits also are useful supplements to sprays and sanitation. Feed additives will aid in preventing fly breeding (primarily house flies) in the manure from animals being fed the larvicide. Feed additives should not be relied upon for total fly control.


Larvicides can be applied directly to maggot-infested manure as a means of temporarily reducing fly numbers when sanitation and manure management cannot be used. Rabon 50WP or Ravap EC at the rate of 1 gallon of finished spray per 100 square feet of surface. See label for mixing instructions. Treat only “hot spots” containing large numbers of maggots, if possible. Do not spray manure where runoff to soil or water can occur. Do not spray animals with these concentrations.

Screening and other mechanical control methods are invaluable in preventing flies from entering milk rooms and milking parlors. Air curtains are also of some use in keeping flies from entering these areas. Fly traps can capture large numbers of house flies but generally do not reduce their numbers significantly. Ultraviolet light traps, bottle traps and fly sticky strips can be useful, particularly in the milk room where pesticide applications are limited and fly numbers are low. The solution to severe fly problems lies in finding and treating or eliminating breeding sites.

Several commercial firms offer fly parasite release programs that can be used to supplement fly control around concentrated livestock operations. These small wasp parasites lay their eggs in the larvae or pupae of house flies. The benefits of a parasite release programs in livestock operations have not been proven. If you try them, include sanitation and chemical treatments with these parasite releases.

Rat-tailed maggots live in highly polluted water such as livestock lagoons and manure pits. Mature larvae crawl away from the area in which they developed to dry places so they can transform to the adult stage, a fly. They become pests when they enter milking parlors or milk rooms. An application of Ravap to the manure pit may provide very limited control. The crawling larvae will stop in a row of dry soil placed in their path. The soil and maggots can be shoveled up and discarded.

Fly control in milk rooms

Pesticides must be used with extreme caution in milk rooms to avoid illegal residues in milk. Nonchemical means such as good sanitation; tight-fitting, spring-loaded screen doors and windows; sticky fly strips; and ultraviolet traps are preferred methods of control supplemented by a comprehensive fly management program in the dairy barn. When pesticides are used, cover milk, milking utensils, bulk tanks and other containers before spraying. Follow label directions and check with your local milk inspector before using any pesticide in the milk room area.

Residual fly sprays (excluding milk rooms)

Insecticides may be applied as residual surface sprays, nonresidual space sprays, baits, manure sprays or feed additives. Always read and follow label instructions before applying insecticides for fly control. Treat walls, ceilings, posts and other fly resting sites. Spray these areas thoroughly and to the point of run-off. In order to minimize control failures due to insecticide resistance, do not apply the same insecticide, or insecticide within the same chemical class (particularly pyrethroids), repeatedly throughout an entire season. See product labels for use rates. Alternate applications of pyrethroids (permethrin) and organophosphates (stirofos, fenthion).

Remove animals from barn before spraying. Allow at least four hours for spray to dry before allowing cows to return to the barn. Application may be made to walls, ceilings, partitions, posts and other fly resting areas. Do not contaminate feed, water or milking equipment, and do not apply these materials in the milk room.

These same materials may also be applied onto fly resting areas outdoors. Apply 1 gallon of spray solution per 500 to 1,000 square feet. Residual fly spray materials should control flies for one to seven weeks.

Baits can provide temporary reduction of house flies, but baits alone will not control fly populations. Never use baits where cattle or other animals can eat them. They should be used along with sanitation and other insecticidal methods (e.g., residual and space sprays). Read the label for further instructions.

Fly control on animals: Stable fly, horn fly and face fly

Dust bags are most effective when set up in a forced-use situation such as at the exit to milking parlors, across barn doors, entrances to watering sites and on feeders.

Use only No. 2 diesel oil, No. 2 fuel oil or label-recommended mineral oil to dilute concentrate. Do not use waste oil or motor oil. Use 1 gallon of oil solution per 20 feet of backrubber. Do not use these dilutions as sprays. As with dust bags, these devices are most effective when placed in force-used areas such as milking room exit doors and entrances to watering sites.

Do not treat calves less than 6 months old. Apply at least 20 minutes before or after milking is completed. Spray lactating cows after milking. Do not contaminate feed, water, milk or milking equipment.

Pour-on insecticides for pasture fly control

Several products containing the active ingredient permethrin may be used on lactating dairy cattle. Examples include Atroban Boss, Brute, CyLence, DeLice, Expar and Permectrin CDS. Other labeled pests include lice and stable flies.

Insecticide impregnated ear tags for lactating dairy cattle

Insecticide ear tags can provide good control of horn flies and may provide some reduction in face fly numbers. Install tags after flies first appear in the spring (late May or early June). Use on calves and mature cattle. Remove tags at the end of the fly season (September or October). If insecticide resistance is suspected, or if pyrethroid ear tags were used the previous year, organophosphate (OP) tags (Cutter Blue) are recommended or switch to other control devices such as dust bags or sprays. Organophosphate ear tags effectively control pyrethroid-resistant horn flies but are somewhat less effective against face flies.

Bolus and feed additives for pasture fly control

Bolus Vigilante 9.7 percent (diflubenzuron) is available for fly control. The active ingredient is gradually released from the bolus and prevents development of face fly and horn fly larvae in manure. Use standard balling gun. For best results, all cattle in the herd should be treated. See the product label for dosage rates.

Feed additives target fly maggots breeding in fresh animal manure. Research results indicate results can be very variable. All animals must eat a minimal dose of a feed additive regularly. Supplementary control measures must be taken to deal with flies moving in from nearby herds. Moorman’s 0.02 percent IGR Cattle Mix (methoprene) at the rate of 0.25 to 0.5 pound per 100 pounds bodyweight per month or Rabon 7.76 percent Premix or 97.3 percent Oral Larvicide (stirofos) fed at the rate of 70 milligrams of active ingredient per 100 pounds bodyweight per day may reduce numbers of some flies on cattle.

Lice and tick control

Insecticides listed for animal sprays can be used to control lice and ticks. In addition, Taktic 12.5 percent EC (amitraz) can be used at the rate of 1 quart per 100 gallons water. The pour-on insecticides Atroban, Delice, Boss, CyLence and Elector can be applied to control cattle lice.

Cattle grub control on nonlactating dairy cattle

Eprinex is the only insecticide labeled for cattle grub control on lactating dairy cattle. The following insecticides can be used to control cattle grubs on dry cows, replacement heifers and bulls. If you treat dry pregnant cows, be sure to observe and follow all waiting periods. If a treated cow should come fresh before the waiting period is up, it will be necessary to discard her milk until the required time has passed. Whenever the systemic insecticides are used as pour-ons or as a spot-on, the weights of the cattle must be estimated or measured to accurately determine the amount of insecticide to be used on the animal being treated. Do not use more insecticide than is recommended on the label. Read the label completely before using any insecticide.

Do not use systemic insecticides in conjunction with organophosphate wormers such as Baymix (coumaphos) or Loxon (haloxon).

Chorioptic mites cause a condition known as barn itch or tailhead mange. Taktic (amitraz) for fly control on animals that contain permethrin as the active ingredient can be used. Two treatments seven to 10 days apart, or as directed by the label, are necessary for control. Eprinex is labeled for control of chorioptic mange mites with no withholding period for the milk or slaughter.

Wound maggots – Catron IV (permethrin) can be used to protect wounds on dairy cattle. Use as directed.

Summary of insecticides for use on dairy cattle

As shown in Table 1 (page 44) a numerical classification system has been developed to make it easy to recognize the modes of action of insecticide products. Insecticides with the same mode of action belong to groups with unique numbers. Selection of a labeled product from a different number category (different mode of action) will help to slow down the development of resistance to either group (for example, alternate use of pyrethroid insecticides and pyrethrin sprays (Category 3) with labeled organophosphate insecticides (Category 1B)). PD

—Excerpts from University of Kentucky Extension website