Dairy cattle-Horn fly

Haematobia irritans

Biology The horn fly was introduced into the United States during the 1800s and spread rapidly across North America. Females lay eggs in fresh cattle manure, which is where immature forms complete development. During warm weather, the life cycle of a horn fly is 10 to 20 days; there are many generations of flies each year. The first flies appear in June or earlier; flies disappear with hard frosts in fall. Both sexes suck blood from cattle and other animals. Horn flies are usually seen on animals' backs and sides. If enough flies are present, this can lead to reduced weight gains or milk production of cattle. However, cattle can tolerate a low density of horn flies without measurable losses. The generally agreed upon economic threshold is 200 horn flies per animal.

Management-mechanical control

• fly vacuum (Spalding Cow-Vac)-Animals walk single file through compartment, and vacuum removes flies to a removable bag for disposal. Works best on grazing dairy, placed where cows return to barn. Requires electrical supply. Manufacturer appears to no longer be making this device; used ones may be available.
• walk-through trap-Animals walk single file through compartment, making contact with strips of canvas or similar that dislodge flies. Flies move to exterior screened walls where they become trapped. For additional details and a downloadable blueprint, see University of Missouri publications:

  https://extension.missouri.edu/publications/g1195

  https://extension.missouri.edu/publications/mx1904c6

Management-chemical control

Ear tags, strips

• abamectin/piperonyl butoxide ear tag (XP 820)-Apply when flies become a problem: 1 tag for up to 3 months control, 2 tags for up to 5 months control. Remove tags at end of fly season or before slaughter.
• beta-cyfluthrin/piperonyl butoxide ear tag (Cylence Ultra)-Apply one tag to each ear of all animals older than 3 months when flies appear. Remove tags at end of fly season or before slaughter.
• permethrin ear tag (GardStar Plus)-Apply one tag per ear on all animals when flies first appear in spring. Remove before slaughter.
• zeta-cypermethrin/abamectin/piperonyl butoxide ear tag (Tri-Zap)-Apply one tag per ear of all animals. Remove at end of season or before slaughter.
• zeta-cypermethrin/piperonyl butoxide ear tag (PYthon; PYthon II; PYthon MagnuM)-Apply one tag per head of all animals at least 3 months old when flies appear in spring. Remove tag at the end of fly season or before slaughter.
• zeta-cypermethrin/piperonyl butoxide strips (AmeriAg)-For use on AmeriAg mineral feeders. Apply 10 strips to feeder as directed; replace as needed.

Pour-ons, sprays

• coumaphos spray (Co-Ral Fly & Tick Spray)-Mix 1 quart per 50 gal water. Spray to complete wetting to run-off. Treat no more than 6 times/year. Do not apply more than 1 quart per 50 gal water to non-lactating dairy cattle within 14 days of freshening. Do not apply less than 10 days apart.
• cyfluthrin pour-on (CyLence)-See label for dosing instructions. Pour along top of back and head of cattle of all ages. Repeat as needed but no more than once every 3 weeks.
• dichlorvos spray, concentrate (Vapona [40.2%]; Nuvan Fog2EC [25%], Fog4EC [41.4%], Fog5%;)-Dilute to 1% solution (follow label directions) and apply 1 to 2 fl oz of solution per animal (per day) as a fine mist spray. Do not wet hide. Do not treat calves under 6 months of age. Do not apply within 1 day of slaughter.
• dichlorvos spray, ready-to-use (Prozap Beef & Dairy RTU)-Apply 1 to 2 oz per adult animal as a mist to wet hair. Use proportionately lower rates for smaller animals. Do not exceed 2 oz per animal per day. Should not come in contact with lactating dairy cow teats unless washed with an approved solution. Do not soak skin or wet hide.
• diflubenzuron/permethrin pour-on (Clean-Up II; Lice-Ban)-Apply 3 mL per 100 lb body weight to maximum of 30 mL. Retreat as needed, but no more than once every 2 weeks.
• eprinomectin pour-on (Eprinex)-Apply at 1 ml/10 kg (22 lb) body weight. Apply along midline of back.
• permethrin spray, ready-to-use (various manufacturers; 0.25%-1%)- Spray animal as directed.
• permethrin spray, concentrate (various manufacturers; 10%-40%)-Dilute in water as directed. Spray animal as directed. Typical application interval is 14 days, as needed, but follow label.
• permethrin pour-on (various manufacturers; 1%-10%)-Apply to animal as directed. Typical application interval is 14 days, as needed, but follow label.
• permethrin/piperonyl butoxide spray, ready-to-use (various manufacturers; 1%)-Apply to animal as directed. Typical application interval is 14 days, as needed, but follow label.
• permethrin/piperonyl butoxide spray, concentrate (various manufacturers; 10%)-Dilute in water as directed. Spray animal as directed. Typical application interval is 14 days, as needed, but follow label.
• permethrin/piperonyl butoxide pour-on (various manufacturers; 0.125%-10%)-Apply to animal as directed. Typical application interval is 14 days, as needed, but follow label.
• pyrethrins spray (PyGanic Livestock & Poultry Insecticide; PyGanic Specialty)-Dilute as directed. Spray to thoroughly wet hair. Repeat at intervals of 5-12 days or as needed. Do not exceed 1 treatment per day. This organic product is OMRI listed.
• pyrethrins spray (Tersus 5%)-Dilute in water as directed. Apply to wet hair thoroughly. Repeat treatment as needed, but do not apply more than once per day.
• pyrethrins/piperonyl butoxide spray, ready-to-use (various manufacturers; 0.1%-0.5%)-Apply to animal as directed. Typically, treat daily as necessary but follow label for treatment interval.
• pyrethrins/piperonyl butoxide spray, concentrate (various manufacturers; 0.96%-6%)-Dilute in water or oil as directed. Spray animal as directed. Typically, treat daily as necessary but follow label for treatment interval.
• pyrethrins/permethrin/piperonyl butoxide spray (Pystol Farm & Dairy Aerosol)-Thoroughly spray entire animal for 2 to 4 seconds from approximately 2 ft away.
• pyrethrins/piperonyl butoxide/N-octyl bicycloheptene dicarboximide spray (SSI-50)-Spray entire animal from two-foot distance as it's being released to pasture.
• pyrethrins/permethrin/piperonyl butoxide spray (Raze) -Spray about 3 seconds per side. Do not spray into eyes. Repeat treatment when flies are troublesome.
• tetrachlorvinphos/dichlorvos spray (Ravap EC)-Mix 1 gal in 200 gal water or 2 oz in 3 gal water. Spray with up to 0.5 gal per animal. Do not treat calves under 6 months of age. Take care to not get spray on teats and wash teats if treatment comes in contact. Do not treat more than once per day.
• soybean oil/peppermint oil/cinnamon oil/lemongrass oil/garlic oil (Purely Green Bio-Pesticide Super Concentrate)-Dilute product at 1 to 2 fl oz per gal water.

Backrubbers (oil)

• coumaphos (Co-Ral Fly & Tick Spray)-Mix 4 quarts in 13 gal fuel oil to coat backrubber. Suspend at a height that dairy cattle won't straddle. Do not use diesel or home furnace oil (fuel oil). Recharge as needed.
• permethrin (various manufacturers; 1%-40%)-Use undiluted or dilute in oil as directed. Recharge as needed.
• permethrin/piperonyl butoxide (various manufacturers; 0.125%-10%)-Use undiluted or dilute in oil as directed. Recharge as needed.
• tetrachlorvinphos/dichlorvos backrubber (Ravap EC)-Mix 1 gal in 25 gal approved oil and use in mechanical rubbing device or burlap or rope backrubber. Recharge as needed.

Dusts

• coumaphos dust (Co-Ral 1%)-Place bags so they hang 4 to 6 inches below animals' backline. Direct applications of 2 oz per animal may be repeated no more frequently than 10 days apart and no more than 12 applications in 12 months.
• permethrin dust (various manufacturers, 0.25%)-Place bags so they hang 4 to 6 inches below animals' backline. Direct applications of 2 oz per animal may be repeated as needed but no more than once every 3 days.
• zeta-cypermethrin/piperonyl butoxide dust (PYthon Dust; PYthon II Dust)-Apply in dust bag, shaker, dusting glove, or mechanical duster. Place bags so they hang 4 to 6 inches below animals' backline. Direct applications of 2 oz per animal may be repeated as needed but not more often than once every 3 days. Do not use concurrently with insecticide ear tags containing zeta-cypermethrin or cypermethrin.

Feed supplements (prevent development of flies in the manure of treated cattle)

• diflubenzuron feed supplement (ClariFly 0.04%; ClariFly 0.67%; ClariFly 8%; JustiFly 3%)-Mix into grain according to label to provide 0.1 mg ai/kg (4.55 mg/100 lb) body weight per day (follow table on label). Start feeding early in spring before flies appear and discontinue when cold weather limits fly activity.
• diflubenzuron mineral tub (Vitalix ClariFly #5 Tub)-Provide free choice with targeted consumption of 1.6 oz per 100 lb of cow per day (~one tub per 15-25 head). Provide before flies appear until end of fly season.
• (S)-methoprene premix (Altosid IGR Custom dry blending premix 2%, 10.5%; Altosid liquid 1%)-Use formulas on label to determine proper amounts to mix with feed or minerals. Begin use 30 days prior to fly season; continue feeding until cold weather restricts horn fly activity.
• (S)-methoprene mineral tub (Vitalix Mineralix fly tub with IGR; Vitalix No. 5 "IGR" fly tub)-Feed free choice with one tub for every 15-25 head of cattle. Place tubs out before flies appear and continue use until cold weather marks end of fly season.
• tetrachlorvinphos feed supplement (Rabon 7.76)-Include in diet or supplement at 70 mg per 100 lb body weight daily. See Mixing Guide for additional details.