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Brand: GARDSTAR ® PLUS Insecticide Ear-Tag

Company: Y-TEX

DELIVERY FORM: «ear-tag» to be applied to the front or back of the ear.


CHEMICAL CLASS of the active ingredient(s):

INDICATIONS: CATTLE (beef & dairy)

PARASITES CONTROLLED* (spectrum of activity)

* Country-specific differences may apply: read the product label.


  • For control of susceptible horn flies, attach one tag to one ear of each animal. Tags remain effective up to 5 months.
  • For season-long control of Gulf Coast ticks and face flies, attach two tags per animal (one in each ear).
  • All mature animals in the herd should be tagged.
  • Remove tags at end of fly season or prior to slaughter.


  • LD50 (acute oral) in rats: >5000 mg/kg (for the tag, according to MSDS)
  • LD50 (acute dermal) in rats: >5000 mg/kg (for the tag, according to MSDS)

Suspected poisoning? Read the article on permethrin 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.

2nd-generation synthetic pyrethroids (e.g. cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, permethrin, etc.) are irritant to the eyes and the skin, both of humans and livestock. However, delivery through insecticidal ear-tags is usually less irritant than through pour-ons.

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 (Haematobia irritans) and houseflies (Musca domestica) to synthetic pyrethroids (incl. permethrin) is widespread worldwide, and can be very high, regardless of the delivery form (ear-tag, pour-on, spraying, dust bags, etc.). Cases of resistance to synthetic pyrethroids have also been reported in stable flies and little houseflies, but strength and prevalence is usually low.

This means that if this product does not achieve the expected efficacy against the mentioned parasites, it can 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 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. Since ear-tags with organophosphates are also available in most countries, 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 horn flies, a few ones also as ear-tags. Macrocyclic lactones formulated as 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
GENERIC BRANDS available? YES., perhaps not with permethrin, but with a comparable synthetic pyrethroid.

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

For an overview on the most used insecticidal EAR TAG brands click here.


GARDSTAR PLUS Insecticide Ear-tag for Cattle from Y-TEX is one of the numerous insecticide-impregnated ear-tags for the control of flies & lice on cattle. 

Permethrin is one of the first Type-II synthetic pyrethroids introduced already in the 1970s by several companies (FMC, ICI, SHELL, etc.). 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) horn flies is usually excellent, because they spend most of their time on cattle and thus are exposed to the insecticide for a long period of time. And they remain mainly in the back of the animals, where the concentration of active ingredient released by the ear-tags is rather high. But as already mentioned, horn flies have developed high resistance to all synthetic pyrethroids in the USA and elsewhere. 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". Permethrin has 4 isomers, 2 cis, and 2 trans. Manufacturers of active ingredients usually supply the raw material in standard mixtures, for permethrin typically in a 25:75 or 40:60 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 40:60 mixture is more potent than a cis:trans 25:75 mixture. Qualities with a 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.

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