DELIVERY FORM: «feed additive» to be mixed with the food

ACTIVE INGREDIENT(S): Diflubenzuron 0.04% (= 0.4 g/kg)

CHEMICAL CLASS of the active ingredient(s): benzylurea, insect growth regulator


PARASITES CONTROLLED (spectrum of activity)

  • Larvae of horn flies (Haematobia irritans), face flies (Musca autumnalis), houseflies (Musca domestica) and stable flies (Stomoxys calcitrans) in manure of pasture and confinement cattle and calves, including veal calves.


  • Daily feeding rates:
    • Cattle: 0.10 mg/kg bw
    • Horses: 0.15 mg/kg bw
    • Swine: 020-0.30 mg/kg
  • Read the product label for further details
  • It is highly recommended to start treating at the beginning of the fly season in spring, before flies have become a problem, and to continue treatments until the end of the fly season in fall.


  • LD50 (acute oral) in rats: >4640 mg/kg for the a.i. difubenzuron
  • LD50 (acute dermal) in rats: >2000 mg/kg for the a.i. difubenzuron

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

  • Meat: Nil
  • Milk: Nil

As all IGRs, diflubenzuron acts on biochemical mechanisms that are not found in birds or mammals. For this reason it is quite safe for humans, livestock and pets.

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


Risk of resistance? YES

There are reports on housefly (Musca domestica) resistance to diflubenzuron in several countries, mainly in poultry or swine operations. Cross resistance with organophosphates was found in several cases.

This means that if this product does not achieve the expected efficacy against the mentioned parasites, it may be due to resistance and not only to incorrect use, which is usually the most frequent cause of product failure.

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

These alternative products may not be available in all countries, or not available as feed additives.

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, several in the USA. This product itself contains generic difubenzuron.

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

Click here for an overview on the most used antiparasitic feed additives and medicated feeds for livestock and horses.


This product is a classic feed-through larvicide for cattle, horses & swine that contains generic diflubenzuron. It is marketed by WELLMARK.

Diflubenzuron is a so-called Insect Growth Regulator (IGR) belonging to the group of the benzoylphenyl ureas (also called benzoylureas, BPUs). It was introduced in the late 1970s (by PHILIPS-DUPHAR). It is moderately used in sheep against blowfly strike and lice in a few countries (e.g. New Zealand, Australia), and in livestock premises and environment against houseflies and other flies. Usage in ruminants and horses is very modest wordlwide. It is not used in pets. It is also used in agriculture and against household pests.

Diflubenzuron, as all BPUs, is a Chitin Synthesis Inhibitor (CSI). Chitin is a component of the cuticle of insects, which is an essential part of their outer skeleton. If chitin is not properly produced, fly maggots die when they attempt the next molt and adult flies do not develop, thus their reproductive cycle is interrupted. All BPUs (e.g. diflubenzuron, triflumuron) exert this effect on almost all kinds of insects, also on beneficial ones, which makes them rather harmful for the environment if they are disposed of uncontrolled into water or soil.

As all IGRsdiflubenzuron does not kill adult flies at all, and it does not immediately kill the fly maggots (larvae) either, i.e. it has no knockdown effect. Larvae will die at their next attempt to molt to the next developmental stage, which may take 1-4 days to occur, depending on age of the maggots at the time of treatment, humidity, temperature, etc. This means that they are excellent for the control of fly populations, but nor for quick knock-down of adult flies or fly larvae.


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.