10/09/2022
Beef cattle production represents a multibillion dollar industry in the southeastern United States. External parasites (ectoparasites) are those that live and feed on the outside of the animal. These pests directly affect the producer’s bottom line by causing decreased weight gain, decreased milk production, loss in hide value, and potential disease transmission. Lack of external parasite control costs beef producers billions of dollars each year.
Integrated Pest Management
To be successful in the control of external parasites, producers need to take an integrated approach to pest management. Integrated pest management (IPM) uses a variety of pest control tactics (biological, cultural, and chemical control) to reduce overall pest pressure. IPM strategies are pest specific and will vary based on the biology of the pest you are trying to control; therefore, proper pest identification should always be the first step in the process.
Biological Control
Proper identification of insect populations is imperative to make sound pest control decisions, as many of the insects that we encounter are harmless to both humans and animals. Some insects are even beneficial in the fight against common cattle pests either through predation or competition for resources. Examples include black dump fly larvae, which are known to feed on house fly larvae developing in the same manure. Soldier fly larvae will outcompete horn fly and house fly larvae for food, which leaves the pests without the necessary resources to fully mature. Some of the more commonly discussed biological controls in livestock operations are dung beetles and parasitic wasps. Dung beetles will actively remove manure, making the pats dry faster and the environment unsuitable for fly development. Several species of parasitic wasps, marketed as biological controls of cattle pests, are commercially available. The wasps lay eggs inside immature horn flies, house flies, and stable flies. The wasp larva then eats the immature flies. It should be noted that wasps can be used to supplement sanitation but probably will not control pests below economic thresholds. This is especially true when the environment favors pest development.
Cultural Control
Cultural controls are practices that manipulate the pest’s environment to reduce conditions that are suitable for development. Make sure to quarantine and treat new animals before they are introduced into the herd to reduce chances of lice, mite, or tick infestations. Reducing breeding conditions through proper management and sanitation is the most effective way to control cattle pests.
Use hay rings or roll out hay to reduce waste. Trampled hay that is urinated or defecated on is the primary breeding site of many cattle pests.
Avoid feeding hay in the same location each time.
Use pasture rotation and proper stocking rates to allow manure to dry out and decompose.
In areas where cattle congregate, remove manure and spread thinly on pastures to allow it to dry properly.
Remove and dispose of carcasses quickly and properly.
Keep pastures cut or properly grazed to decrease thatch and associated moisture, which aid in pest development.
Keep water troughs clean and in proper working order. Eliminate areas that hold stagnate water to reduce mosquito breeding sites.
Chemical Control
Many pesticides are available that are labeled for external parasites of beef cattle. Pesticides should be used only when other methods are ineffective or unavailable. Economic thresholds, the point at which chemical control measures are economically justified, should be used when making treatment decisions. Always read and follow label directions. The pesticides listed in this document are meant only as a reference guide, not as full label directions or recommendations.
Insecticide Application Methods
Dips
Dip vats are used to treat a large number of animals in an efficient manner. Vats provide good coverage of the animal being treated to ensure effective control. Use only products labeled for dip vat treatments and follow directions when filling and recharging.
Dusts
Most commonly, dusts are applied using self-treatment dust bags that are recharged throughout the season. Place dust bags in areas where animals are forced to use them: heading toward feed troughs, waterers, and mineral feeders, for example. Dust bags are most effective when placed at the animals shoulder height. Placing dust bags under cover will allow them to stay dry and prevent caking.
Ear Tags
Ear tags deliver slow-release insecticide over time via a plastic tag placed in the ear of the animal. Ear tags typically control flies for 3 to 5 months and ear ticks for 4 to 5 months. They do a good job of controlling horn flies, stable flies, lice, mosquitoes, and ticks. Follow the label in regard to the number of tags per animal. Most brands require two tags per mature animal; applying fewer than the recommended rate will not save money but will increase pest resistance to the insecticide.
Feed-Throughs
Feed-through products are insecticides that are mixed with either feed or mineral supplements. They pass through the animal’s digestive system and control immature flies developing in the manure. Adult flies will migrate from nearby herds, so feed-through products are most effective when the herd is isolated from other herds or used in addition to a topical treatment method. Consistent intake is imperative, so animals need unlimited and continual access to the feed/mineral for the products to be effective. Feed-throughs take time to build up in the system and become effective, so make sure to follow the label about when to start (typically 3 to 4 weeks before fly season) and finish feeding products during the fly season. Feed-through insecticides are not digested, so the products never get into blood or meat; therefore, they have no effect on adult flies.
Injectables
Some active ingredients are formulated for sucutaneous injection in beef cattle. These products are labeled for cattle grubs and lice as well as for internal parasite control.
Pour-Ons
Pour-on products are made to be applied down the length of the animal’s backline and sometimes down the center of the face. They are then absorbed into the skin and act as systemic insecticides. They may control horn flies for up to 30 days.
Spot-On
These systemic products are applied to a specific area along the animal’s back. They require specially designed applicators and are most effective for control of cattle grubs and lice.
Sprays
Sprays are meant to be applied as a coating across the entire animal. Only mix and prepare the amount needed to treat the number of animals. Do not store or use mixed insecticides. Emulsifiable concentrates or soluble formulations are well suited for small sprayers. Wettable powders require a high-volume piston pump sprayer with agitator. For ticks, lice, and mites, use enough water to cover the animal thoroughly. When spraying systemic insecticides to control cattle grubs, be sure to wet the animals to the skin.
External Parasites of Beef Cattle in the Southeast
Horn Fly
Close up of horn flies (Haematobia irritans) on a black cow.Horn flies (Haematobia irritans) are one of the most economically important pests of beef cattle in the United States. Adult horn flies are small (3/16 inch) and are similar in color to house flies. They spend most of their adult life on the animal (back, sides, and belly) where they feed on blood 30 to 40 times per day, using piercing mouthparts that inflict a painful bite. Their persistent biting causes cattle to react with evasive maneuvers (tail flicking, side licking, stomping, kicking their bellies, huddling together). Cattle spend more time trying to rid themselves of horn flies than they do eating or drinking, leading to weight loss, decreased milk production, dehydration, and weakness. Adult horn flies live about 3 weeks and leave the animal only to lay eggs under the edge of fresh manure pats. Development takes approximately 10 to 20 days. When horn flies exceed the economic threshold of 200 flies per side, weight gain will be affected, and calves can lose up to 15 percent of their body weight. Use of chemical controls is necessary once this economic threshold is reached
Chemical control options come in a variety of delivery methods: back rubs, dust bags, ear tags, feed-throughs, injections, pour-on liquids, and sprays. Different delivery methods will work depending on your herd management plan. Make decisions based on your system.
Wait to use topical control measures until you reach the 200 flies per side economic threshold.
Rotate chemical classes of insecticides each season to prevent resistance.
Remove ear tags at the end of each fly season or when the tags become ineffective (economic threshold is reached).
Avoid combination ear tags because they promote resistance to multiple insecticide classes simultaneously.
Place back rubs and dust bags in areas where cattle are forced to use them; good examples are gates that cattle must go through to access water, feed troughs, or mineral feeders. It may take time for cattle to become acclimated to these devices.
When using insect growth regulator feed-through products, begin to feed early in the spring and feed through the first frost. Consistent intake is essential, so make sure animals have constant, equal access to the product.
Stable Fly
Stable flies (Stomoxys calcitrans) have a major economic impact to the US cattle industry. Adults feed on the blood of the animal and are painful biters. Unlike horn flies that stay on the animal, stable flies will feed once per day and then leave the animal to rest on nearby surfaces (vegetation, barn walls, etc.). Adults are similar in size to house flies (about 1⁄4 inch long), and they lay their eggs in decaying vegetation that has been mixed with urine or f***s. Stable flies will attack the legs, sides, backs, and bellies of cattle, causing evasive maneuvers (stomping, belly kicking, tail switching, bunching). Cattle spend more time trying to rid themselves of flies than eating or drinking, leading to weight loss, decreased milk production, dehydration, and energy loss. Extreme bunching can also reduce the cattle’s ability to dissipate heat during the hot and humid days of summer. Chemical control action must be taken when the economic threshold of two to four flies per leg is noted
Remove old or trampled hay bales.
Use hay rings to reduce waste and to reduce amount of hay that will be trampled, urinated, and defecated on.
Rotate hay feeding locations to reduce accumulation and to allow previous hay feeding locations to dry properly.
Remember that biological controls that attack horn fly larvae will also attack stable fly larvae.
Spray animals and resting sites with approved insecticides to provide immediate control.
Pesticide Suggestions for Horn Flies and Stable Flies
a comprehensive list of available chemical control products labeled for horn flies and stable flies. Alabama Extension does not promote one product over another. Make sure to read and follow all label instructions and guidelines. The table is organized by insecticide formulation, then by class of insecticide. Rotation between insecticide classes is key to successful resistance management.
