To achieve effective horn fly control with Altosid® IGR, just follow these simple instructions:

  • Begin feeding Altosid® IGR to your animals before horn flies appear in the early spring. Continue to feed Altosid® IGR during the summer months and then into fall. One general rule is to feed 30 days before the last frost and 30 days after the first frost in the fall. 
  • If mixing Altosid® IGR with free-choice feeds, such as mineral supplements, put out a five- to seven-day supply and protect it from rain. 
  • Use one feeder for every 15 to 20 animals. 
  • Place the feeders near watering holes or loafing areas. 
  • Check feed consumption for a few days. Increase or decrease the number of feeders, or move them if necessary, to allow for proper consumption.

When used as directed, Altosid® IGR alone usually provides excellent season-long control. If fly populations exceed acceptable levels due to migration from untreated neighboring herds, use an approved adulticide, such as Prolate/Lintox-HD™, to decrease the fly population.


(S)-Methoprene belongs to the terpenoid class of compounds, as do natural products, such as essential oils and other plant-produced materials.


Persistence and Movement in Soil: The half-life of (S)-Methoprene under aerobic conditions in sandy loam is approximately ten days when applied at the exaggerated rate of 1000 g/Ha. Most of the applied dose is converted rapidly to CO2. (S)-Methoprene remains bound in the top few centimeters of the soil even after repeated washings with water. Thus, it should not persist, leach or contaminate ground water.

Fate in Plants: When applied at the rate of 1000 g/Ha on alfalfa, (S)–Methoprene has a half-life of less than two days and less than one day on rice. It is metabolized rapidly, yielding products that are further degraded to normal plant nutrients.

Fate in the Food Chain: In a model ecosystem study, it was shown that (S)-Methoprene does not accumulate in the food chain. It was demonstrated that biodegradation and lack of persistence characterize (S)-Methoprene in the environment.

Persistence in Water: In the field, (S)-Methoprene has a half-life of 30-45 hours in unsterilized pond water. If the water is exposed to sunlight, the half-life is significantly reduced.


An extensive toxicological database has been generated to support EPA registrations of products containing (S)-Methoprene. (S)-Methoprene products exhibit a wide margin of safety and no acute handling hazard by any exposure route.


(S)-Methoprene is not a teratogenic compound.

The NOEL for maternal and embryotoxicity in rabbits was 200 mg/kg/day. The NOEL for reproductive effects in rats was 500 ppm.

(S)-Methoprene is not a mutagenic compound.


Extensive laboratory and field experiments have shown that (S)-Methoprene is rapidly degraded by mammalian metabolic systems and readily converted to natural body constituents. When steers or cows are treated orally with (S)-Methoprene, the compound is excreted either unchanged or metabolized quickly and eliminated via urine, feces and expired breath. Chemical identification of (S)-Methoprene degradation products in milk and blood one week after the oral administration of radio labeled (S)-Methoprene to a cow revealed that it was metabolized to simple acetates that are mostly incorporated into fatty acids, lactose and cholesterol. (S)-Methoprene metabolites were not detected in tissues. In a cow and growing steer, unmetabolized (S)-Methoprene was mainly excreted through feces, whereas up to 19.8% of the orally administered dose was excreted in urine as radioactive metabolite. The highest radioactivity was in bile, and the next highest was in the liver. All muscles of the cow had < 0.1 ug of the total radioactivity per gram.


Residual insecticides, such as organophosphates, are toxic to beneficial insects, such as coprophagous flies and beetles, predaceous beetles, parasitic wasps and dung beetles. Altosid® IGR does not disrupt dung composition and does not harm beneficial insects.


Horses (1/dose group) have been experimentally dosed with (S)–Methoprene, as follows, without adverse clinical signs or loss of appetite. Accidental exposure to (S)-Methoprene via cattle feed would not be anticipated to pose any toxicological risk.


(S)-Methoprene is an insect growth regulator (IGR) with activity against fleas, mosquitoes, horn flies, ants, sciarid flies and stored product pests.

The active ingredient, (S)-Methoprene, was first registered by the EPA in 1975. (S)-Methoprene was classified as the first biochemical pesticide and therefore is currently regulated by the Biopesticide Division of the EPA.

(S)-Methoprene has completed an extensive reregistration process, resulting in the publication by the EPA of the Reregistration Eligibility Document (RED) in 1991.

In June 2003, the Environmental Protection Agency (EPA) announced that (S)-Methoprene is exempt from the requirement of a tolerance in or on all food commodities when used to control insect larvae. The EPA granted the exemption because a thorough risk analysis showed residue tolerances are not necessary to protect human health or the environment.

After discussions between the EPA and FDA, it was decided that feed-through uses of (S)-Methoprene in cattle feed to control horn flies should be regulated by the EPA. Altosid® IGR Feed-Thru was the first (S)-Methoprene cattle product registered by the EPA in 1975.


The following excerpt from the 2005 Feed Additive Compendium summarizes the regulatory status of the use of (S)-Methoprene in cattle feed.

FDA Status: No feed mill license required. Product is a food additive. 40 CFR 180.1033 (EPA) (S)-Methoprene is exempted from the requirement of a tolerance in or on all food commodities when used to control insect larvae. When used in medicated feeds, medicated feed application requirement is determined by regulatory status of the drug.

EPA Status: Product is a pesticide when used in non-medicated feeds. EPA registration is required for feeds offered for sale except when custom blended per the provisions of 40 CFR 167.3. In medicated feeds, the product is a food additive and no EPA registration is required when the source of (S)–Methoprene is an EPA-registered product.