Treatment Guidelines for Pasture Flies, Horn Flies and Face Flies

Treatment Guidelines for Pasture Flies, Horn Flies and Face Flies

By Lee Townsend, Extension Entomologist

Horn fly control can mean an additional 12 to 20 pounds of weight per calf over the summer months and can result in less weight loss per nursing cow as well. Horn fly numbers can be kept below the 100 fly per side treatment threshold with a variety of methods so factors such as cost, convenience, physical layout, and animal movement between pastures should be considered when designing a control program.

There is no good information on the number of face flies needed per animal to cause an economic loss. These flies are very annoying but even heavy infestations do not seem to reduce the rate of weight gain. Face flies can carry pinkeye from animal to animal in the herd but outbreaks of this disease occur even when there are no face flies around.

Dust bags are most effective when used in forced-use situations especially where cattle have to pass under them daily to get to water or mineral. Hang bags where cattle will have daily access to them. Keep dust bags dry and charged. Do not use Ectiban or Permectrin if pyrethroid resistance is suspected or present. See ENT-42 "Dustbags for Cattle Insect Control" for more information on forced-use dustbags. Co-Ral 1% D (coumaphos), Ectiban or Permectrin 0.25%D (permethrin), Methoxychlor 5% Dust, or Rabon 3% D formulations are available for use in dust bags.

When using back rubbers, mix the insecticide with a good grade of mineral oil (diesel oil evaporates more quickly and is harder on the cattle's skin. Do not use motor oil. For horn fly control, saturate weekly using one gal oil per 20 feet of backrubber. Backrubbers are more effective against face flies if 18" strips of cloth are tied at four to six inch intervals along the length. Do not use these dilutions as sprays. Service the devices at least once per week and position in entryways to water or mineral feeders. For more information on backrubbers see ENT 4 "Making and Using a Cattle Backrubber" available from your county extension office.

Products for Back Rubbers and Face Rubbers

Amount/gal oil
(ratio of insecticide to oil)
Days To Slaughter
Co-Ral 11.6% EC (coumaphos)
1-1/4 cups (1:13)
Delnav 30% EC or 15% EC (dioxathion)
13 Tbs (1:20) or 26 Tbs (1:10)
Back Side, Ectiban 5.7% EC, Insectrin, Permectrin II 10%
6.5 Tbs (1:40)
1 qt / 20 gal
Lintox-HD (phosmet)
1 qt in 50 gallons (1:100)
Ravap 28.7% EC (stirofos+dichlorvos)
9 Tbs (1:28)

  Large walk through fly traps, placed at pasture gates where animals must pass through them regularly, can reduce horn fly numbers by up to 70% without the use of an insecticide. Ideally, the tunnel-like trap should be placed where animals can pass through it several times a day. Flies are brushed off of the animals while they are in the device. The flies move through the angled side slats to light and are trapped between the slats and the outer screened sides of the trap. Horn flies die naturally after a short time off of the animal. Dead flies that accumulate in the trap can be removed but scavenger insects will do an effective cleanup job if the trap is not cleaned. The traps are not effective against face flies. Plans are available from the UK Entomology Department.

  Insecticide ear tags can provide good control of horn flies and may provide some reduction in face fly numbers. Horn fly resistance to the synthetic pyrethroid permethrin has become a significant problem in Kentucky. See ENTFACT 501, Managing pyrethroid-resistant horn flies.
Install tags after flies first appear in the spring. Use on calves and mature cattle. Do not apply Cutter 1, Terminator, Patriot, or Optimizer tags to calves less than 3 months old. Remove tags in Sept or Oct. If insecticide resistance is suspected, or if pyrethroid ear tags were used the previous year, use an organophosphate (OP) tags or (Cutter Blue,or switch to other control devices such as dust bags or sprays.

Insecticide Impregnated Ear Tags (number of tags per animal)

Synthetic Pyrethroid Tags (P)
Max-Con (cypermethrin + chlorpyrifos) (2)
Atroban Extra, Apollo, Deckem, Ectiban, Ectrin, Ear Force, Expar Extra, Gard Star Plus, New Z Permethrin, Permectrin Insecticide Ear Tags
(10% permethrin) (2)
Perma-Tect II (10% permethrin + 6.6% chlorpyrifos) (2)
Cutter Gold (10% cyfluthrin) (2) Organophosphate Tags (OP)
CyLence Ultra (beta-cyfluthrin) (2) Commando (36% ethion)
Ectrin/Starbar / Insecticide Cattle Ear Tags (2)
(8.6% fenvalerate)
Co-Ral Plus (20% coumaphos + 20% diazinon)
Python / ZetaGard (zeta-cypermethrin) (1) Cutter Blue (20% fenthion) (2)
Saber Extra/Excalibur
(10% lambda-cyhalothrin) (2)
Dominator/Rotator/Tomahawk (pirimifos methyl) (2)
Combination Tags P + OP Optimizer / BovaGard/ X-Terminator (20% diazinon) New Z Diazinon (with synergist) (2)
Double Barrel (6.8 % lambda-cyhalothrin + 14% pirimophos methyl) (2) Patriot (40% diazinon) (1) Cutter 1 (1 per animal for horn fly control 2 to suppress face flies)
Ear Force Ranger (10% permethrin + 6.6% chlorpyrifos + synergist) (2) Warrior / Diaphos Rx (30% diazinon + 10% chlorpyrifos) (2)

Pour-ons for Pasture Flies This application option provides three to four weeks of horn fly control.
Insecticide Days to Slaughter
Atroban, Back Side, Back Side Plus, Boss, Brute, DeLice, Durasect, Expar, Permectrin CD, Permectrin CDS-, Ultra Boss (permethrin) 0
CyLence 1% (cyfluthrin) 0
Dursban 44 PO (chlorpyrifos) 14 See label
Elector (spinosad) 2
Ivomec 0.5% (ivermectin) 48
Lysoff 7.6% PO (fenthion) 21-35
Sabre 1% (l-cyhalothrin) 0

Animal Sprays for Pasture Flies
Insecticide Amt/25 gal water Days to Slaughter
Atroban 11% EC, GardStar EC
Permectrin II 10%
25%WP (permethrin)
- 1 pt
12 oz
Co-Ral 11.6% EC
25% WP
1 pt
Del-Phos 11.6 EL phosmet 1 qt 0
Ectiban 5.7% EC 1 qt 0
Elector (spinosad) See label 2 (horn flies)
Methoxychlor 50WP or 25 EC 2 lbs or 2 qts 0
Rabon 50% WP 1-1/3 lb 0
Ravap 28.7% EC 1/3 gal 0
Use a power sprayer for complete coverage. Do not contaminate feed or water. Do not use sprays containing permethrin if horn fly resistance to pyrethroids is suspected.

Feed additives target fly maggots breeding in fresh animal manure. Research results indicate that 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. Feed additives include Moorman's 0.02% IGR (methoprene) at the rate of 1/4 to pound per month and Rabon 7.76% Premix or 97.3% Oral Larvicide (stirofos) fed at the rate of 70 milligrams of active ingredient per day.

An insecticide bolus is a large pill-like formulation that is given to the animal with a standard balling gun. For best results, the entire herd should be treated. Vigilante 9.7% (diflubenzuron) or Inhibitor (methoprene) are available in bolus formulations. The active ingredient, both are insect growth regulators, is gradually released from the bolus and prevents development of face fly and horn fly larvae in manure.