Discover Entomology at Texas A&M University - Extension Publication E-208: Protecting Cattle from Horn Flies
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E-208
8/11
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Protecting Cattle from Horn Flies

Sonja L. Swiger and Jeffery K. Tomberlin*
*Assistant Professor and Extension Entomologist, Texas AgriLife Extension Service;
Assistant Professor, Texas A&M University; The Texas A&M System

Horn flies resting on the back of a cow. Photo: Jeff Tomberlin, Texas A&M University
Figure 1. Horn flies resting on the back of
a cow. Photo: Jeff Tomberlin, Texas A&M
University

The most damaging insect pest for beef cattle in Texas is the horn fly (Fig. 1). Research shows that a calf infested with more than 200 horn flies will weigh 15 to 50 pounds less at weaning. Horn fly feeding on dairy cows can also reduce milk production up to 20 percent. To suppress horn flies effectively and economically:

Identifying horn flies

Horn flies look like house flies and stable flies but are slightly smaller (Fig. 2). Like the stable fly, horn flies have piercing mouthparts. To distinguish horn flies from stable flies, observe their feeding behavior. Horn flies rest on an animal between feedings; stable flies remain on the animal only while feeding. Also, horn flies feed most often on an animal’s back, shoulders, and sides, whereas stable flies feed principally on the legs.

Life cycle

Horn flies resting on the back of a cow. Photo: Jeff Tomberlin, Texas A&M University
Figure 2. Comparison of the horn fly to the stable fly, house fly, and
face fly. Photo: Photo: John B. Campbell, University of
Nebraska-Lincoln

Horn flies lay eggs in fresh manure pats, where they hatch as maggots. They develop from the egg to the adult stage within 10 to 20 days and live for about 3 weeks, feeding 20 to 30 times a day. In Central Texas, horn flies are usually first observed in early spring. Populations tend to peak in early summer, then decline when the weather becomes hot and dry. In the fall, horn fly populations usually surge again when the temperatures drop and rainfall increases. Generally, they are no longer a problem after October or November, depending on when temperatures start to drop.

Control methods

To suppress horn fly populations efficiently, use an integrated pest management (IPM) approach. IPM relies on multiple tactics including cultural, biological, and chemical methods to suppress insect pests.

Biological control: Parasitic wasps suppress horn fly populations naturally. Producers who want to use parasitic wasps to control horn flies can order fly pupae parasitized with the wasps from insectaries in Texas or across the United States. The parasitized pupae are best used around barns where manure accumulations allow for the development of fly pests. However, research has not proven that releasing parasitic wasps suppresses horn flies or that the use of parasitized pupae reduces them in pasture situations.

Dung beetles and fire ants also suppress horn fly populations. Dung beetles compete for manure use and shrink the manure pats where horn fly larvae grow. Be careful when applying pesticides— moxidectin and, to a greater extent, avermectin kill dung beetles. Fire ants feed on horn fly larvae and pupae, thus reducing the number of horn fly adults. Fire ant control is effective when horn fly populations are small, but as they increase in the summer, the impact is not as apparent. A walk-through trap designed to collect horn fly adults from cattle can also lower populations. For more information and design instructions, see http://extension.missouri.edu/publications/DisplayP ub.aspx?P=G1195.

Cultural methods: Remove and properly dispose of fresh manure from barns and stalls to interrupt the horn fly’s life cycle and help prevent new populations from developing.

Chemical control: Several chemical control methods can help reduce the number of horn flies on cattle: ear tags, sprayers and dusters, feed additives, and boluses. To prevent resistance, rotate chemical classes of insecticide products each year— and even within a year—if a mid-to-late season horn fly increase warrants further insecticide applications.

Ear tags
Ear tags (Table 1) are 2- to 3-inch plastic tags impregnated with an insecticide and attached to a cow’s ear. Several insecticides are formulated for use in ear tags and many brands are available. This large selection can make it difficult to decide which tag to use. For descriptions of several types of ear tag products, see http://insects.tamu.edu/extension/publications/ epubs/eee-00047.cfm. These guidelines will help you use ear tags effectively:

Sprayers and dusters
Free-range cattle can be treated with small sprayers and dusters powered electrically from the back of a truck. Although sprays (Table 1) can also be applied during seasonal roundups, they usually do not suppress horn flies for long.

Feed additives
Confined and free-range cattle can be given feed additives that suppress horn flies. These products contain insecticides that pass through the animal’s digestive system and remain in the manure where horn fly maggots develop. But, the herd will still be susceptible to biting flies moving from neighboring properties. One disadvantage of feed additives is that it is difficult to regulate each cow’s feed intake. Some animals might take in the proper amount; others might receive too little.

Boluses
Another method for controlling horn flies is boluses, which look like large pills. Boluses are retained in the cow’s reticulum (second stomach) and dissolve slowly, releasing the insecticide into the digestive tract. Unlike feed additives, boluses release the insecticide continuously in the manure and kill immature horn flies. However, the herd will still be susceptible to biting flies from neighboring properties.

Summary

Regardless of the method you choose, follow these guidelines:

Acknowledgments

Ed Bynum, Allen Knutson, and Chris Sansone, Extension entomologists with the Texas AgriLife Extension Service, and Ron Swiger reviewed this manuscript.

Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age or national origin. Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Edward G. Smith, Director, the Texas AgriLife Extension Service, The Texas A&M University System. Revision The

Insecticide and Dosage Method Comments
Sprays
Permethrin (Pyrethroids)

GardStar 40 percent
4 fl oz / 25 gal water
4 fl oz / 25 gal water

Atroban 11 percent EC
1 pt/50 gal water
Permectrin II
8 oz/50 gal water


High pressure spray
Low pressure spray



Use 0.5 to 1 gal spray per


1 qt coarse spray per animal.
See label for other spray considerations.


1 qt coarse spray per animal.

Rabon + Vapona

Ravap
23 percent + 5.3 percent =
2 qt/100 gal water

 


Use 0.5 to 1 gal spray per animal

Treatment interval no less than 10 days.
No waiting period.

Pour-ons
Cyfluthrin 1 percent

CyLence

Ready-to-use

Read the label for proper rate based on
weight of the animal.

Gamma-cyhalothrin

StandGuard

Ready-to-use

Read the label for proper rate based on the weight of the animal.

Lambda-cyhalothrin

Saber

Ready-to-use

Read the label for proper rate based on the weight of the animal.

Ultra Saber

Ready-to-use

Read the label for proper rate based on the weight of the animal.

Permethrin: pyrethroids

Synergized DeLice 1 percent
+ 1 percent PBO1
0.5 fl oz /100 lb body weight

Brute 10 percent

Atroban 1 percent–DeLice
Permectrin CDS
Boss

Ready-to-use
Maximum 5 fl oz / animal


Ready-to-use

Ready-to-use
Ready-to-use
Ready-to-use

Pour along the back of the animal. Do not treat more often than every 14 days.
PBO1

Follow label directions. Read the label for proper rate based on the weight of the animal.

Ultra Boss

Ready-to-use

 

Ear Tags
Organophosphate tags:

Diazinon 18-21 percent
Terminator II
Optimizer

Read the label.

Follow label directions.

Diazinon 40 percent
Patriot

Diazinon 30 percent +
Chlorpyrifos 10 percent
Warrior

Pirimiphos-methyl 20 percent Read the label. Follow label directions.
Dominator

Diazinon 35 percent +
Coumaphos 15 percent
Corathon

Read the label.


Read the label.



Read the label.

 

Read the label.

Follow label directions.


Follow label directions.

 

Follow label directions.

 

Follow label directions.

Pyrethroid tags:

Permethrin 10 percent
GardStar Plus

Read the label.

Follow label directions.

Beta-cyfluthrin 15 percent
CyGuard

Read the label.

Follow label directions.

Zeta-cypermethrin 10 percent +
PBO1 20 percent
Python
Python Magnum

Read the label.

Follow label directions.


PBO1

Lambda-cyhalothrin 10 percent +
1PBO 13 percent
Saber Extra

Read the label.

Follow label directions.

Combination ear tags with pyrethroids:

Lambda-cyhalothrin 6.8 percent +
Pirimiphos-methyl 14 percent
Double Barrel

Read the label.

Follow label directions.

Backrubber applications

Mix the insecticide formulations listed below as directed on the label for use in homemade or commercial backrubbers. Backrubbers are most effective when placed in a forced-use situation such as gateways, doors, or alleyways. Install them so that all animals use them once a day. If backrubbers cannot be installed in a forced-use situation, place them in areas where animals often loaf. To be effective, backrubbers must be maintained and filled often. Use only No. 2 diesel fuel, No. 2 fuel oil, or an approved backrubber oil to mix insecticides for backrubbers. Do not use fresh or used motor oils.

Coumaphos

Co-Ral 11.6 percent ELI

Co-Ral 5.8 percent
Livestock Insecticide Spray (LIS)
4 qt/13 gal (9.75 oz/gal) of
No. 2 fuel oil or No. 2 diesel fuel

Restricted-use pesticide

Backrubbers only

 
Malathion

Malathion 57 percent EC
2.25 pt/4 gal of No. 2 diesel fuel

Backrubbers

Follow label instructions for mixing.
No waiting period before slaughter for
or approved backrubber oil

Rabon + Vapona

(Ravap) 23 percent + 5.7 percent
1 gal/25 gal diesel or
5 oz/1 gal diesel

 

 

Permethrin

Permectrin 10 percent EC
1 qt/20 gal No. 2 diesel fuel or
approved backrubber oil

GardStar 40 percent EC
4 oz/10 gal No. 2 diesel fuel or
suitable mineral oil

Permectrin II
1 qt/20 gal No. 2 diesel fuel or
approved backrubber oil

Atroban 11% EC
1 pt/10 gal No. 2 diesel fuel or
approved backrubber oil
Synergized DeLice 1 percent + 1 percent
1PBO
1 pt/gal No. 2 diesel fuel or
approved backrubber oil.

 













PBO1

Phosmet

Prolate
1 gal/50 gal No. 2 diesel fuel or
approved backrubber oil

 

 

1PBO = piperonyl butoxide, a material that increases the effectiveness of some pyrethrin and pyrethroid insecticides

The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Texas AgriLife Extension Service is implied.