Identifying Horn Fly Infestations

Discover how to identify and control horn fly infestations on your operation to keep your cattle comfortable and your profits high.

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Horn Fly Population Guide

How Many is Too Many?

An effective control program keeps horn fly levels to fewer than 200 flies per animal. This at-a-glance guide will help you easily evaluate the effect that horn flies currently have on your herd. It’s easiest to make the most accurate estimate in the morning, when horn flies are on the upper sides of the cows.

So Effective. And So Easy to Use.

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


To maximize beef cattle in a cow calf operation, begin feeding Altosid® IGR to your cattle 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 average daily daytime temperatures reach 65 degrees and 30 days after the first frost in the fall. We call it the 30/30 Program, a proven strategy for achieving economical horn fly control.


If mixing Altosid® IGR with free-choice feeds, such as mineral supplements, put out a five- to seven-day supply and protect it from the rain.


To ensure cattle are consuming enough of the feed-through fly control, use one feeder for every 15 to 20 animals.


Keep the horn fly control supplement accessible to cattle by placing the feeders in areas where cattle congregate, such as 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 horn fly control. If fly populations exceed acceptable levels due to migration from untreated neighboring herds, use an approved adulticide, such as Prolate/Lintox-HD™ Insecticidal Spray & Backrubber for Livestock to decrease the fly population.

Get Certified

Looking to learn more about fly contol?

For additional information on how you can protect your cattle from horn flies using Altosid® IGR and an integrated pest management (IPM) strategy, become certified in Centralized Fly Control.

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