Organic Broadcaster

Thwart external livestock parasites with prevention, organic controls

By Joe Pedretti, MOSES

External parasites on livestock can lead to economic loss for producers. Studies have shown that even moderate infestations of parasites could cost you one pound of milk/meat production per head per day. In a well-managed organic herd or flock with good freedom of movement, excellent nutrition, and strong immune systems, most para­sites will not cause long-term harm. But, when conditions are ideal for the parasite or when ani­mals are stressed, parasites can cause significant problems.

Animals stressed by parasites are at greater risk of secondary diseases and other health problems. The combination of direct and indi­rect losses add up too quickly for parasites to go untreated. Conventional farmers typically take care of the entire parasite problem in one step by using a pour-on pesticide like ivermectin, insec­ticidal dusts, insecticidal ear tags and feed addi­tives. Organic farmers cannot use these synthetic solutions and must counter common parasite infestations through a combination of prevention and approved organic control.

Just what is a parasite? The simplest defini­tion is that a parasite is something that lives at the expense of something else, known as the host. Parasites do not generally kill a host, but they can weaken it, and in some cases, transmit diseases. Parasites can be viruses, bacteria, fungi, animals, and even plants. Parasitism has proven to be a successful evolutionary niche. Parasites are classi­fied as either “endoparasites,” living inside a host’s body (viruses, worms) or “ectoparasites,” living either on or outside of the host’s body. This article will focus on ectoparasites that cause economic damage to domesticated livestock in the Midwest and northern climates.

Common External Parasites


Source: Michigan State University

Lice are wingless insects that complete their entire life cycle on the host. Lice that affect livestock are “host specific” and cannot live on humans or even other animals. Human lice are an entirely different species and cannot infest livestock.

Five species of lice affect cattle in the U.S. One spe­cies is a biting or chewing louse; the other four are sucking lice. Lice obtain their food by puncturing the skin of the animal with their mouthparts and suck­ing blood. Each time they feed, they puncture the skin at a different place.

The major external parasite attacking hogs is the hog louse. These insects ob-tain their food by puncturing the skin of the hog with their mouthparts and sucking blood.

Source: University of California

Lice spread from animal to animal through direct contact or through shared bedding and sleeping/loafing areas. Lice can reproduce very quickly in the right conditions, and tend to be more of a problem dur­ing the winter months in the Midwest, when ani­mals are more tightly confined. Stress also can be a factor, as can age of livestock—young animals are more susceptible to infestation.

Livestock infested with lice will display in-creased scratching, rubbing, and biting of infested areas. Affected animals have a generally unthrifty appearance, rough coat, and lowered production. In severe infestations, there may be a loss of hair, bleeding and skin scarring. Extreme infestations of sucking lice can cause anemia, and animals may go off feed.

Lice in cattle and small ruminants tend to congregate around the ears, neck, topline, tailhead, escutcheon and tail switch. Part the hair in these areas and look for live lice and the presence of nits (eggs). Lice attach their eggs to the base of hairs in the infested areas. Nits will look like white specks on a dark hair coat. Live lice will look dark against light skin, especially when engorged with blood.

In hogs, lice tend to congregate in the skin folds of the neck and jowls, behind the ears and on the inside of the legs. Look for live lice and nits in these areas. Hogs tend to scratch and rub them­selves incessantly when infested with lice.

Lice attach their eggs (nits) to the base of hairs.
Photo by Colorado State University.


Mites are not insects, they are more closely related to ticks and spiders, belonging to a group of animals known as arachnids (eight legs). There are thousands of mite species, but only the “mange mites” are a significant parasite of domesticated animals.

There are two species of mange mites that most often affect cattle. Chorioptes bovis is commonly known as “tailhead mange.” It is the most common type of mange found in the U.S. It is a problem primarily in winter in all types of cattle, but espe­cially in dairy cattle which are housed in closed quarters.

The bare patches around this steer’s eyes are a typical indication of mange.
Photo by Colorado State University.

Sarcoptes scabiei var. bovis is a burrowing mite that infests cattle and is frequently referred to as “neck and tail mange,” although it may be found on any part of the body.

Mange mites are very small and burrow into the surface of the skin, so identification is primar­ily done through the symptoms, which are loss of hair in patches around the eyes, ears and along the back line of the animal. Tailhead mange mites show similar symptoms, but primarily on the rump. Infested animals will scratch and rub these areas constantly, to the point of rubbing them raw and bleeding.

Hogs with mange will scratch so much the skin bleeds and scabs.
Photo by North Carolina State University.

In hogs, mange usually starts around the ears and head and moves back along the spine. The affected areas often take on a dry, flaky or leather-like appearance. Active mites cause irritation that makes the infected hogs scratch themselves some­times so much so that the skin becomes raw.

Lice and Mange Prevention

Quarantine new arrivals for up to three weeks and carefully watch and inspect them for signs of lice, mange and other diseases. It is much easier to treat a few animals than an entire herd.

Clean out and disinfect barns between herds. Lice and mange mites cannot live long off of the host, so a two-week gap between animal groups will kill them.

There is a link between nutrition and infesta­tion. Healthy, unstressed animals tend to have much less of a problem with lice and mange. Feed free choice minerals and kelp, especially to young stock. Sulphur has been shown to inhibit lice, so add this to your free choice or lick options. Aloe, fed as pellets or as liquid, and apple cider vinegar will stimulate the animal’s immune system.

Exposure to sunlight and allowing ample housing space will help minimize lice infestations —lice and mange prefer darkness, humidity, and closely confined animals.

Maintain closed herds if possible. Cull animals that consistently susceptibile to lice infestation.

Treating Lice and Mange Organically

Enzymatic Soap

Soap kills insects by stripping away their waxy cuticle. When combined with an enzyme that weakens the insects’ exoskeletons, this product kills lice by dehydrating them. This is one of the best options of lice control on cattle, small rumi­nants and hogs. It is completely non-toxic. It is labor-intensive to apply, especially if you have a large herd and a bad infestation. You also must reapply it in seven days to kill the newly hatched lice, since the soap will not kill the eggs (nits).

Crystal Creek makes an enzymatic soap, “Lice and Mange Wash.” It’s available at

Pyrethrum and PyganicOil

Pyrethrum powder applied as a dust directly to the animal will kill lice. Make sure to get the version without piperinyl butoxide. Pyrethrum is natural and has low mammalian toxicity. It is best to apply the dust outdoors and to wear a mask when applying. Pyrethrum also can be mixed with diatomaceous earth and used in traditional dust bags hung in walkways or lanes (keep it dry). Pyrethrum will need to be reapplied after seven days to kill hatching nits.

Pyganic™ is pyrethrin (derived from chrysan­themum flowers) mixed with soybean oil. It can be sprayed directly on infested areas. It works in two ways: the pyrethrum kills through direct action and the oil clogs the breathing pores of the lice and mange. Pyganic can be used in oilers and rotating brushes for continuous application to the herd. Reapplication may be necessary to kill hatching nits.

Do not reuse old hanging dust bags or oilers. Buy new ones to avoid contamination with syn­thetic (prohibited) materials.

Essential Oils and Other Oils

Apply essential oils at 1 part essential oil with 2-3 parts vegetable oil rubbed in to the affected areas. Essential oils such as anise, camphor, eucalyptus, pennyroyal, rosemary and sassafras will work. Essential oils suffocate the lice, may slow down their reproduction, and act as a repel­lent/irritant. Agri-Dynamics sells a product of aromatic oils ready-made for this purpose called Ecto-Phyte™. A similar product is De-lice and Mange Spray™ from Dr. Sarah’s Essentials.

Rather than using prohibited kerosene, diesel or other petroleum-based products, apply a thin coat of vegetable oil such as soybean or sunflower oil to suffocate insects. Mineral oil is allowed as an external treatment under USDA NOP stan­dards. These oils suffocate the lice and mange mites.


Neem has been used to control insects for centuries. It is made from a tree native to India and controls insects by acting as an anti-feedant, repellent, and egg-laying deterrent.

Livestock expert Gearld Frye uses this method to control lice with neem: “I’ve found that the best combination is about 2 oz. of neem oil mixed with water and applied with a garden sprayer to their coats. Then we take a mixture of approximately 4 parts neem powder, 2 parts turmeric powder, and 10 parts diatomaceous earth—all certified organic from Mountain Rose Herbs. With the oily mixture on their coats, we take cupfuls of the Neem powder mixture and rub it into their coats mainly along the top line, but down around their necks and haunches and base of the tail where lice seem most prevalent.” (Gearld Frye, Ameri­can Herbataurus)

Special Note on Ivermectin

The National Organic Standards do allow for the restricted emergency use of the synthetic par­asiticide ivermectin to control external parasites. You must obtain permission from your certifier to use ivermectin to control external parasites such as mites and lice, and must follow the rules and conditions for use:

(18) Parasiticides—Prohibited in slaughter stock, allowed in emergency treatment for dairy and breeder stock when organic system plan-approved preventive management does not prevent infestation. Milk or milk products from a treated animal cannot be labeled as provided for in sub­part D of this part for 90 days following treat­ment. In breeder stock, treatment cannot occur during the last third of gestation if the progeny will be sold as organic and must not be used dur­ing the lactation period for breeding stock.

(ii) Ivermectin (CAS #70288-86-7).


Ticks, like mites, are arachnids, and are mostly a nuisance pest, but under certain condi­tions they can reach numbers capable of affecting the animal, and they can transmit disease. Ticks prefer the ears and neck areas of cattle where it is difficult for the animal to remove them. Fortu­nately, ticks have a complex life cycle and it is not possible for them to breed and reproduce on the animals or in buildings.Cattle, sheep and goats can contract Lyme disease from infected deer ticks, but diagnosis of Lyme disease in livestock is difficult and mimics other physical disorders.

The best way to control ticks is to minimize animals’ access to woodland areas. Aromatic essential oils have shown some repellent action against ticks. Ticks are very tough to kill, since they have a thick exoskeleton. Soaps and most other organic treatments do not work well. Physi­cal removalPyganic™ and are your only real con­trol options once ticks are attached to the animal.


Not all flies are parasites. Many fly species are nuisance pests, but are not parasites. However, there are several species that do feed on the blood of domesticated animals, and can, if their num­bers are high, cause economic losses. Parasitic flies also can cause severe discomfort.

Horn flies are about half the size of house flies, are dark gray and have piercing mouthparts. They are blood-sucking flies that stay on the shoulders and backs of cattle almost continuously. During extremely hot weather or when it rains, they may move to the protected underside of the animal.

Source: Michigan State University

Stable flies are sometimes called biting house flies due to their similar appearance. Stable flies feed primarily on legs and lower abdomen of cattle by penetrating the skin and feeding on the blood two to three times a day depending on the weather. Once full, they move to a resting place, usu­ally in the shade, to digest their meal. The blood loss and pain associated with the bite of stable flies results in substantial economic loss.

Source: University of Kentucky

Deer flies are black or dark brown in color, about the size of a house fly, and can be recognized by their triangular shape and bright red or green eyes. Horse flies are very similar to deer flies, but are sig­nificantly larger. Only the females need to feed on blood. They do this to obtain the nutrition needed to lay eggs. Both deer flies and horse flies have an aquatic life cycle where the eggs are laid in marshy, wet areas and the larval stage develops in these wet soils. Because of this complex life cycle, they are very difficult to control.

Fortunately, deer and horse flies are mainly a nuisance pest, and do not occur in large enough numbers to inflict substantial physical damage. Still, they are highly annoying to livestock. They use scissor-like mouthparts to slash open a wound to drink the blood. Their saliva prevents blood coagulation, and creates a histamine reac­tion (large swelling at the bite). For this reason, livestock often will stop eating to seek refuge from deer and horse flies.

Preventive Control Options for Flies

Sanitation and manure management are key to controlling horn and stable flies. Clean out pens, exercise areas, feed bunks, hutches and stalls frequently (minimum 1x weekly). These flies will breed in spilled, wet feed, so do not neglect areas under bunks and in other feeding areas.

Muscovy ducks are well known as voracious eaters of fly larvae and pupae; chickens are also a good option. A small flock allowed to patrol outside pens and around hutches can bring down fly populations. Some farmers are follow­ing their cattle with chickens in the grazing rotation to pick through cow patties to reduce fly numbers.

Fly parasites offer good control if released on a regular basis. These tiny wasps parasitize the fly pupae by laying their eggs inside them. The developing wasp larva literally eats the fly alive before it can become an adult. You can buy fly parasites and have them delivered to your door by companies like IPM Laboratories (ipmlabs. com), Kunafin (, and Rincon-Vitova (


Research has shown that animals deficient in certain minerals are more attractive to parasitic flies. Free choice minerals, kelp and specialized mineral mixes like Flies be Gone™ from Agri- Dynamics can help offset deficiencies and make animals less palatable to blood-feeding flies.

Active Control Options (Adult Fly Control)

Put up fly paper and fly tape in the barn, and keep it fresh. Tape and paper loses stickiness quickly due to dead flies and dust. Tape rolls make it easy to expose fresh tape.

Fly trap barrels work extremely well. A new design by organic dairy farmer Kevin Jahnke expands and improves upon the idea behind smaller scented fly traps. Kevin takes 55-gallon plastic barrels and cuts a rectangular square in the top and glues in a clear piece of plastic or plexiglass. Around the perimeter of the barrel, about halfway up on four sides, he cuts holes and inserts plastic PVC tubing with 90 degree elbows pointing towards the bottom of the bar­rel. He then fills the barrel with about 8 inches of water and “scents” the trap with rotting food and manure. The flies enter the trap through the PVC tubes, smelling a nice environment to lay eggs, but instinctively fly up towards the light and cannot escape, eventually dying in the trap. These can be placed anywhere on the farm, including grazing paddocks. Kevin shares instructions for building this fly barrel in the May|June 2012 Organic Broadcaster. (See, click on Broad­caster and then Archives.) Or, watch Kevin explain the process on video, available at you­ (search “fly barrel”).

Epps Biting Fly Trap™

The Epps Biting Fly Trap™ kills about one pound of biting flies daily.

In a three-year study conducted by Cornell University, the Epps Biting Fly Trap™ killed an average of one pound of biting flies each day. The trap requires no electricity, chemical or messy baits—it uses just soapy water. The trap mimics the color and outline of cattle and horses, which attracts biting flies. They hit the trap and drop into the soapy water where they cannot escape. Then they drown.

Walk-through Fly Traps

Walk-through traps, also known as the “Bruce Trap” after the entomologist who designed it, have been around for a long time and have proven to be cheap, easy to maintain, and very effective at reducing horn and stable flies. The walk-through trap is placed in a lane that all animals must pass through on their way to and from the pasture or other communal area. Hanging strips of canvas, plastic or other flexible material brush the flies off the animal’s face and back. The trap has two layers of screen­ing on the outside walls with small, one-way holes between them. The flies instinctively try to escape by going towards the light, and get trapped between the two layers of screening.

The trap was designed for cattle, but can be modified to accommodate smaller ruminant animals. Most animals are reluctant to pass through the trap at first, so some training will be necessary. Detailed instruction can be found through the University of Missouri at extension.

Repellent Sprays

Aromatic essential oils will repel flies (and gnats, which are also from the fly family). The challenge is to apply the oil to the top and under­side of the cow with enough coverage to repel flies. It will have to be reapplied frequently. Spraying the animals right after milking in the morning is a good strategy. Some farmers keep a small pump sprayer in the parlor and give them a shot on top and underneath after milk­ing. These oils also can be added to oilers and brushes so cattle can reapply it themselves.

Several companies make good, ready-made, essential oil repellents:

• No-Fly fly repellent (Crystal Creek)

• Ectophyte Insect Repellent (Agri-Dynamics)

• Shoo-Fly (Dr. Sarah’s Essentials)

Insecticidal Sprays and Oils

Natural pyrethrin sprays can be sprayed on animals to kill flies or on problem areas where they congregate. Be careful however, many of these sprays contain compounds like piperinyl butoxide that are prohibited for use in organic production. Pyganic™ is a favorite because the oil base gives it longer activity. Sprays for flies are considered “restricted use,” meaning that you can only use these insecticides if your other control methods have failed to give sufficient control.

Special Note

Always confirm the status of any new live­stock product with your certifier before use. Some “natural” products may contain synthetic or natural ingredients that are prohibited in organic production. Most “allowed” products are actually “Restricted Use.” So ensure that your certifier is aware of the change to your input list and to your Organic System Plan, and that you are using the product for its intended use. Follow all label instructions and consult your veterinar­ian when serious health problems are apparent.

Joe Pedretti is a MOSES Organic Specialist.

From the July | August 2014 Issue

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