Brand: PHYTON ® Insecticide CATTLE EAR-TAG

Company: Y-TEX

FORMULATION: ready-to-use dust for treating animals


  • Zeta-cypermethrin: 10% = 100 g/kg
  • Piperonyl butoxide: 20% = 200 g/kg

CHEMICAL CLASS of the active ingredient(s):


PARASITES CONTROLLED(spectrum of activity)


Beef & Dairy (incl lactating) Cattle

  • Summer Season: To control horn flies for about 3-4 months and aid in control of face flies, apply 1 tag per animal in late spring. To control horn flies, face flies, lice, Gulf Coast ticks and Spinose ear ticks for 4-5 months, and to aid in control of stable flies, black flies, house flies and small horse flies, apply two tags per animal (1 in each ear) when flies appear in spring. Apply 2 tags to large bulls for optimum horn fly protection.
  • Winter Season: For seasonlong lice control, apply tags in late fall. To control biting lice, shortnosed sucking lice and aid in control of other sucking lice, apply 1 tag per calf or 2 tags per mature animal (1 in each ear).
  • All animals in the herd should be tagged.
  • Remove tags as recommended by the manufacturer.


  • LD50 (acute oral) in rats: >5000 mg/kg (according to MSDS)
  • LD50 (acute dermal) in rats: for the a.i. >2000 mg/kg (according to MSDS)
  • Estimated hazard class according to the WHO: U, unlikely to present acute hazard

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

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

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

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

Cypermethrin and all other 2nd-generation synthetic pyrethroids (e.g. cyhalothrin, deltamethrin, permethrin, etc.) are irritant to the eyes and the skin, both of humans and livestock. But irritation is usually worse when using pour-ons than after spraying.

Cypermethrin and all synthetic pyrethroids (e.g. cyhalothrin, deltamethrin, permethrin, etc.) are extremely toxic to 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 cleaning equipment or disposing of equipment washwaters.

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


Risk of resistance? YES; resistance of horn flies and houseflies to synthetic pyrethroids (incl. zeta-cypermethrin) is widespread in the USA and worldwide, and can be very high. Cases of resistance of stable flies and little house flies to synthetic pyrethroids have also been reported, but their prevalence is usually low.

The synergist in the formulation (PBO) is supposed to neutralize resistance of parasites to synthetic pyrethroids. However, PBO works only against the so-called metabolic resistance (enhanced detoxification) caused by mixed function oxidases (= MFO), which is one among several mechanisms by which parasites can become resistant to synthetic pyrethroids and pesticides of other chemical classes. PBO specifically inhibits the activity of MFOs. If metabolic resistance is caused by other enzymes than MFOs, or if resistance is (also) due to other mechanisms such as target site insensitivity, reduced penetration or behavioral modifications, it won't be neutralized by PBO. In the vast majority of cases producers or pet owners facing parasites resistant to synthetic pyrethroids do not know which mechanisms make the parasites resistant, and it is mostly not possible to find it out. Consequently, whether the synergist PBO helps to overcome resistance or not is in fact a lottery.

This means that if this product does not achieve the expected efficacy against the mentioned parasites, it may be due to resistance and not to incorrect use, which 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 as ear-tags, or may not be effective against all the concerned parasites.

It has been shown in the USA that horn flies resistant to synthetic pyrethroids are more susceptible to diazinon, an organophosphorous insecticide. This although resistance of horn flies to organophosphates has also been reported, but weaker than to synthetic pyrethroids. To our konwledge such a higher susceptibility to diazinon of pyrethroid-resistance flies has not been confirmed for buffalo flies in Australia, but it is likely to be the case. Since ear-tags with organophosphates are also available, a very reasonable strategy to prevent or at least delay resistance development is to rotate each year between these two chemical classes. Even better is to add a macrocyclic lactone (abamectin, doramectin, eprinomectin, ivermectin, moxidectin, etc.) into the rotation scheme, because the mechanism of action of these compounds is different from those of organophosphates and synthetic pyrethroids. Most macrocyclic lactones are available as pour-ons for the control of buffalo flies, a few ones also as ear-tags. Injectables and drenches do not control flies or other external 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, New Zealand
GENERIC BRANDS available? YES, not necesarily with zeta-cypermethrin, but with comparable permethrin. PHYTON Insecticide CATTLE EAR-TAG is a brand from Y-TEXcontaing generic zeta-cypermethrin.

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

For an overview and a list of the most used insecticide-impregnated ear-tags click here.


This product is one of the various insecticide-impregnated ear-tags containing a synthetic pyrethroid for the control of flies & lice

Zeta-cypermethrin is one of several standard isomer mixtures of cypermethrin (see below). Cypermethrin is one of several Type-II synthetic pyrethroids introduced by ICI & SHELL in the 1970s. Worldwide it is massively used in veterinary products as well as in agricultural and hygiene pesticides.

Insecticide-impregnated ear-tags are designed to slowly release the insecticide into the animals hair-coat to ensure protection for months. Whether most of the insecticide is released at the beginning and only a little at the end, or release is homogeneous depends on the composition of the matrix and the behavior of the active ingredient(s) in it. However, after 2 to 3 months the amount released progressively decreases to drop below the amount that is required to ensure full fly control. This means that at a certain point flies and other parasites may be exposed to sub-lethal doses, which is generally considered as a factor that favors resistance development. For this reason the tags should be removed after 3-4 months following the manufacturer's use recommendations, and either replaced by new ones or the animals should be left untagged.

Once the active ingredient is released, efficacy strongly depends on the spreading of the active ingredient(s) along the animal's hair coat to other parts of the body. This depends on factors such as solubility of the active ingredient in the hair and skin lipids. Persistence in the hair-coat depends on other features of the active ingredient(s) such as volatility, resistance to sunlight, solubility in water, etc. As a general rule, some body parts will get less active ingredient than other parts and protection there will be lower, e.g. the legs, the underbelly, the udders, below the tail, etc.  Animal behavior (licking, grooming, rubbing, etc.) plays a role as well. It has been shown, that if only half of the animals in a herd are tagged, those untagged will also be protected against flies, indicating that part of the active ingredient is transferred from tagged to untagged animals. However, this also means that tagged animals will lose part of the active ingredient and protection will be shorter and/or control will be poorer.  For this reason all animals in a herd should be tagged because this reduces the impact of animal behavior in efficacy and protection. However, since individual animal behavior plays a role in efficacy and length of protection, it must be accepted that protection will not always be the same in all the animals in a herd.

All synthetic pyrethroids are veteran pesticides developed in the 1970s-1980s 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 of the parasite (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, synthetic pyrethroids 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 synthetic pyrethroids 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. But this is why they are considered rather safe to mammals, both humans and livestock (cats are an exception: pyrethroids are toxic to them!) and why they leave rather low residues in meat and milk.

Control of susceptible (i.e. non-resistant) buffalo flies is usually excellent, because they spend a lot of time on cattle and thus are exposed to the insecticide for a long period of time. But as already mentioned, buffalo flies have developed high resistance to all synthetic pyrethroids in Australia and elsewhere. Biting lice are also exposed to topical insecticides for a long period of time because they never leave the host. In contrast with the behavior of horn flies, stable flies bite the treated animals anywhere in their bodies (often in the legs) and remain attached and thus exposed to the insecticide only during their blood meals that last a few seconds or minutes, which is often too short to kill them. Trying to control housefly populations with on-animal topical products is usually ineffective. The simple reason is that they spend most of their time off-the animals.

All synthetic pyrethroids have a certain repellent effect, mainly on mosquitoes. The repellent effect on flies is weaker than on mosquitoes.

It is useful to know that the active ingredients of many synthetic pyrethroids consist in a mixture of various optical isomers, typically those called "cis", and those called "trans". Cypermethrin has 8 isomers, 4 cis and 4 trans. Manufacturers of active ingredients usually supply the raw material in standard qualities, for cypermethrin typically e.g. in a 40:60 or 80:20 cis:trans ratio. Zeta-cypermethrin is a mixture of 8 isomers with a 48:53 cis:trans ratio. It happens that the efficacy against parasites and the mammalian toxicity of these isomers are significantly different. Typically cis isomers are more effective insecticides but also more toxic to mammals. Obviously a cis:trans 80:20 mixture is more potent than a cis:trans 40:60 mixture. Qualities with higher cis content are usually also more expensive. And the higher the percentage of the most active isomer, the lower the rate that is required for achieving the same efficacy.


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.