Brand: COUMAPHOS Livestock Dust


FORMULATION: dust for treating animals

ACTIVE INGREDIENT(S): Coumaphos: 1% = 10 g/L

CHEMICAL CLASS of the active ingredient(s): Organophosphate


PARASITES CONTROLLED (spectrum of activity)


Beef & Dairy Cattle

  • Against horn flies, lice, face flies
    • Place contents of the package in any commercially available dust bag. Suspend bags in areas frequented by cattle or in gateways or lanes through which the animals pass daily for water, feed, or minerals. Bags may also be suspended in loafing sheds or in front of protected mineral feeders. For lactating dairy cows, bags may be suspended in the exit through which cows leave the milking barn. In all cases the bags should be adjusted so that the bottom of the bag will hang four to six inches below the top-line of the cattle. For reduction of face flies, the bags must be located so the animals will be forced to use them daily and hung at a height to insure that the faces of the cattle will be dusted.
  • Against horn flies, lice - Direct Application.
    • Apply 2.0 ounces of dust per animal by shaker can over the head, neck, shoulders, back and tailhead. Repeat as necessary.


  • Against lice:
    • Direct Application. Apply not more than 1 oz. *(3 level tablespoons) per head as a uniform coat to the head, shoulders, and back by use of a shaker can. Repeat as necessary, but not more often than once every ten days.
    • Bedding Treatment. Apply 2 oz. *(6 level tablespoons) uniformly over each 30 square feet of fresh, dry bedding by use of a shaker can. Repeat as necessary, but not more often than once every ten days.
    • In severe infestations both individual animals and the bedding may be treated as directed above.


  • LD50 (acute oral) in rats: for the a.i.: 13 mg/kg
  • LD50 (acute dermal) in rabbits: for the a.i. 500 mg/kg (according to MSDS)
  • Estimated hazard class according to the WHO: II, moderately hazardous

Suspected poisoning? Read the article on coumaphos safety in this site.

Withholding periods (=withdrawal times) in days for meat & milk (country-specific differences may apply: read the product label)

  • Meat:
    • Cattle: USA NIL
    • Swine: USA NIL
  • Milk for human consumption: USA NIL when used according to label.

WARNING !!!: Never use on humans, dogs or cats.

Coumaphos and all organophosphates (e.g. diazinon, dichlorvos, phosmet, etc.) etc. are highly toxic to birds, fish and aquatic invertebrates. Do not apply directly to water, or to areas where surface water is present or to intertidal areas below the mean high water mark. Do not contaminate water when disposing of equipment wash-waters or rinsate.

You may be interested in the following articles in this site dealing with the general safety of veterinary products:


Risk of resistance? YES; cases of resistance of horn flies to organophosphates have been reported in the USA and elsewhere, but resistance to organophosphates is usually weaker and less widespread than to synthetic pyrethroids (e.g. permethrin). Resistance of most tick species, lice and mites (both of cattle & swine) to organophosphates is usually not a problem in most of the USA.

This means that if this product does not achieve the expected efficacy against horn flies, it may be due to resistance. However incorrect use is usually the most frequent cause of product failure.

Alternative chemical classes/active ingredients to prevent resistance of external parasites through product rotation:

These alternative products may not be available in all countries, or may not be available for dusting, or may not be effective against all the concerned parasites.

Learn more about resistance and how it develops.


Are the active ingredients of this product ORIGINAL* or GENERICS**?


*Meaning that they are still patent protected and generics are not yet available
**Meaning that they have lost patent protection and may be acquired from manufacturers of generic active ingredients other than the holder of the original patent.

COUNTRIES where this brand/product is marketed: USA
GENERIC BRANDS available? YES, but rather few, if at all. COUMAPHOS Livestock Dust is one of BAYER'S 8now ELAnCO) original brands containing coumaphos in the USA.

Click here to learn more about GENERIC vs. ORIGINAL drugs.

For an overview on the most used antiparasitic spray, dip & dust BRANDS click here.


Coumaphos  is an organophosphate discovered and developed by BAYER in the 1950s. COUMAPHOS Livestock Dust is one the the various original brands from BAYER marketed in the USA. In most other countries BAYER's brand for coumaphos products for livestock was ASUNTOL.

Insecticide dusts such as this product are often one of the cheapest options for insect control on animals. However the active ingredients used in such products are mostly rather old (introduced in the 1950s to 1970s) and many pests have developed resistance to them. For cattle, more modern and more effective active ingredients for the control of external parasites are often not available as dusts or concentrates, but only as ready-to-use pour-ons, injectables, or in the form of insecticide-impregnated ear-tags. They are usually more effective, more convenient and with a longer protection period than dusts and concentrates, but are also more expensive.

All organophosphates are veteran pesticides developed in the 1950s-1960s and are basically contact insecticides. This means that when the parasite comes in contact with it (e.g. during the blood meal, after landing on a treated host, etc), the active ingredient that impregnates the host's hair coat penetrates through the cuticle (i.e. the "skin" of insects and other arthropods) into its organism and disturbs essential biological processes in the parasite's body, in this case its nervous system.

After administration to livestock or other animals, organophosphates do not have a systemic mode of action, i.e. they are not transmitted to the parasite through the blood or the host. Topically administered organophosphates are very poorly absorbed through the skin of the hosts, and what is absorbed is quickly broken down and/or excreted. Consequently the concentration reached in the blood is too low to kill blood-sucking parasites.

Dusting is a delivery form of insecticides that is still often used on poultry wordlwide, due to the fact that tat many bird species have the natural behavior of dusting themselves. Although still popular in the USA, use of dusts in cattle and swine is rather unusual in many other countries (Europe, Latin America, Australia, etc). Dusting for self-treatment of livestock (e.g. using dust bags) has an inherent weakness: Dosing depends on the behavior of the animals. It is unavoidable that some animals get too much product, and other animals not enough. Besides insufficient protection of some animals, this may cause excessive residues in other animals. And it is generally accepted that underdosing of animals favors resistance development. For these reasons parasiticides for dusting are no more allowed in many countries (e.g. the EU). To learn more about dusting animals click here.

Control of susceptible (i.e. non-resistant) horn flies is usually good, because they spend a lot of time on cattle and thus are exposed to the insecticide for a long period of time. Lice are also exposed to insecticides for a long period of time because they never leave the host. Control of face flies is often not as good, due to their different behavior: they do not spend a lot of time on the animals and visit mainly body parts in the face that are humid with body fluids (eyes, nostrils, around the mouth), where the insecticide concentration is diluted by these body fluids. Control of other flies (stable flies, horse fliesblack flies) is insufficient after dusting, because they may bite the treated animal anywhere in its body and remain attached and thus exposed to the insecticide only during their blood meals that last a few seconds or minutes, which is too short to kill them.


This article IS NOT A PRODUCT LABEL. It offers complementary information that may be useful to veterinary professionals and users that are not familiar with veterinary antiparasitics. 

Information offered in this article has been extracted from publications issued by manufacturers, government agencies (e.g. EMEA, FDA, USDA, etc.) or in the scientific literature. No guarantee is given on its accuracy, integrity, sufficiency, actuality and opportunity, and any liability is denied. Read the site's DISCLAIMER.

In case of doubt contact the manufacturer or a veterinary professional.