ADM Alliance Nutrition’s IGR is an insect growth regulator (methoprene), which helps break the life cycle of horn flies. More cost-effective horn fly protection can be obtained by controlling immature stages rather than the adults. IGR, a feed-through insecticide, is most commonly added to mineral supplements to prevent the development of horn flies in the manure of treated cattle.

Why use IGR (methoprene) to contain horn fly populations?

• IGR has a long history of effectiveness

• No documented resistancy

• Will not leach out of cattle manure

• Decomposes naturally along with the manure

• Effects only the horn fly pupae and will not harm beneficial insects

• Does not require withdrawal prior to milking or slaughter

• Is not harmful to warm-blooded animals, birds, and reptiles

Why be concerned about horn flies?

• The USDA estimates horn flies cost the cattle industry over $730 million due to lost production.

• Horn flies typically travel no more than a quarter of a mile during their lifetime.

• Horn flies reproduce at tremendous rates. With no treatment program, two adult horn flies can produce over 3.3 million adult horn flies and over 111 million immature horn flies in only eight weeks.

• Each horn fly can bite and suck blood 20 to 40 times daily, causing irritation and blood loss.

• Up to 20% less milk is produced by cows due to decreased grazing time.

• USDA estimates the expected gain loss in growing cattle at 0.25 to 0.5 lb daily or 37.5 to 75 lb over a 150-day grazing season due to ineffective horn fly control.

• Lighter calves are weaned, typically 13 to 14 lb lighter.

• University of Idaho reported yearling heifers lost 0.06 to 0.09 lb of daily gain without horn fly protection.

Won’t Ear Tags, Sprays, Pour-ons, or Dust Products Work Better than IGR?
These products do provide some degree of effectiveness against adult horn fly populations; however, they have no effect on the immature stages of horn flies. In addition, use of ear tags, sprays, pour-ons, and dusts often requires rounding up cattle into working facilities multiple times over the course of the horn fly season. This takes your valuable time and also stresses cattle. Plus, many of these products utilize organophosphates or pyrethroids, which have documented horn fly resistance in many areas. Better season-long horn fly protection can be achieved by controlling immature stages rather than the adult horn flies.

Will Horn Flies Become Resistance to IGR?
There have been no verified cases of resistance to IGR since the product was introduced in 1975. The goal for horn fly protection is to keep the horn fly population below the economic threshold, which entomologists estimate is approximately 200 horn flies per animal. It is not cost effective to totally eradicate horn flies.

How can Cattle Producers Effectively use IGR in a Mineral Program?

• Start feeding IGR before the horn fly season begins.

• IGR must be consumed at least every other day.

• IGR intake should be within the label feeding rate.

• Adequate mineral feeder space is needed, at least 15-20 cattle per feeder.

• Location and number of feeders may need to be adjusted to obtain proper consumption.

• IGR should continue to be fed until the first killing frost. IGR is available in MoorMan’s® Range Minerals with WeatherMaster and MasterGain® Range Minerals with WeatherMaster products.

To view the IGR Technical Bulletins, click on the below links:

• Insect Growth Regulators: Research Compares Different Sources

• Insect Growth Regulators: Research Demonstrates Differences

• Economical Significance of Horn Flies to Cow/Calf Operations

• Horn Flies: Control Methods Change in Response to Government Regulations and Development of Insecticide Resistance

• Guidelines for Selecting Horn Fly Control Program

• Horn Flies Stress Affects Cattle’s Tolerance for Horn Flies

• Feed-Through Products for Horn Fly Control

• Warm Weather Heats up Horn Fly Population

• Economically Significant Parasites of Range Cattle