Biology The horn fly was introduced into the United States during the 1800s and it 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 10-20 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. 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.
- abamectin ear tag (XP 820)-Apply to all animals in herd when flies become a problem in spring. One or two tags/animal. Remove tags at end of fly season or before slaughter.
- beta-cyfluthrin/piperonyl butoxide ear tag (Cylence Ultra)-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.
- diazinon ear tag (OPtimizer)-One tag to each ear of all animals older than 3 months. Remove before slaughter.
- diazinon/chlorpyrifos ear tag (Warrior)-One tag to each ear of all animals older than 3 months when flies appear. Remove before slaughter.
- diazinon/coumaphos ear tag (Corathon)-One tag to each ear on all mature animals when flies appear. One ear tag per calf. Remove tags at end of fly season or before slaughter.
- lambda-cyhalothrin ear tag (Saber Extra)-One tag to each ear on all animals when flies appear in spring. Remove tags in fall or before slaughter.
- lambda-cyhalothrin (6.8%)/pirimiphos-methyl (14%) ear tag (Double Barrel VP)-One tag to each ear on all animals in herd when flies appear in spring. Remove tag in fall.
- permethrin ear tag (GardStar plus)-One tag per ear on all animals when flies first appear in spring. Remove before slaughter.
- pirimiphos-methyl ear tag (Dominator)-One tag per ear on all animals when flies first appear in spring. Remove tags in fall.
- zeta-cypermethrin/piperonyl butoxide ear tag (PYthon MagnuM)-One tag per head of all mature and weaned animals when flies appear in spring. Remove tag at the end of fly season or before slaughter.
- ddvp concentrated spray (Vapona)-Dilute 1 gal in 50 gal water (1% solution) and apply up to 2 fl oz of solution per animal as a fine mist spray. Do not wet hide. Do not treat Brahman animals or calves under 6 months of age. One day withdrawal.
- eprinomectin pour-on (Eprinex, drug)-Apply at 1 ml/10 kg (22 lb) body weight. Apply along midline of back in a narrow strip extending from the withers to the tailhead. No slaughter interval, no required milk discard time.
- gamma-cyhalothrin pour-on (Standguard)-Apply at 10 ml (0.3 fl oz) if < 600 lb or 15 ml (0.5 fl oz) if > 600 lb to backline. Do not apply to face. Repeat as needed but no more than once every 2 weeks and no more than 4 times in a 6 month period.
- ivermectin pour-on (Ivomec, drug)-Apply at 1 ml/10 kg (22 lb) body weight. Do not slaughter within 48 days of treatment.
- permethrin ready-to-use pour on (1%; Atroban)-Apply at 0.5 fl oz (0.005 fl oz or 0.15 ml ai) per 100 lb of body weight to a maximum of 5 fl oz (0.05 fl oz or 1.5 ml ai) per animal. Pour along backline and down face. Treat once every 2 weeks as needed.
- permethrin/piperonyl butoxide pour on (Ultra Boss)-Apply at 3 ml per 100 lb body weight. Maximum of 30 ml (1 fl oz) per animal. Treat once every 2 weeks as needed.
- permethrin spray (Gardstar 40% EC)-Apply at 30 to 118 ml (1 to 4 fl oz) per 25 gal water (0.013-0.05% ai). 1 to 2 quarts high pressure spray over body of animal. For low-pressure spray, apply at 118 ml (4 fl oz) to 2.5 gal water, spray till wet but not to runoff.
- pyrethrins (EverGreen EC 60-6) at 1 to 2 fl oz/gal water. Wet hair thoroughly. Repeat as needed. Also available as aerosol.
- permethrin backrubber or self-oiler (Gardstar 40% EC)-Apply at 118 ml/10 gal mineral oil or diesel oil. Keep rubbing device charged. Results improve with forced daily use.
- permethrin dust (several brands, 0.25%)-Suspend bags where cattle congregate. Place bags so they hang 4 to 6 inches below animal's backline. Direct applications of 2 oz per animal may be repeated as needed.
- zeta-cypermethrin/piperonyl butoxide dust (PYthon)-Apply in dust bag, shaker, dusting glove, or mechanical duster. Suspend bags where cattle congregate. Place bags so they hang 4 to 6 inches below animal's backline. Direct applications of 2 oz per animal may be repeated as needed but not more often than once every 3 days.
- diflubenzuron feed supplement (Clarifly 0.04%)-Prevents development of immature forms in manure of treated animals. For confined beef cattle, mix into grain according to label to provide 0.1 mg ai/kg (4.55 mg/100 lb) body weight/day. Start feeding early in spring before flies appear and discontinue when cold weather limits fly activity.
- (S)-methoprene premix (Altosid IGR Custom 2%)-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 (SweetCake)-Feed free choice. Offer one tub for every 15-25 head of cattle, and remove all other self limiting nutritional supplements. Tubs should be placed where cattle congregate (watering, loafing, shade areas). Cattle should consume an average of 0.8 ounces of product per 100 lb of animal body weight per day. Deploy tubs before flies appear and continue use until cold weather marks end of fly season.
- tetrachlorvinphos mineral block (Sweetlix Rabon)-Feed free choice. 1 block for 5 head of cattle. See label for details.