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Horn Fly Resistance Management

A short generation length coupled with a high reproductive rate play a significant role in the development of insecticide resistance by horn flies.

Effective horn fly control requires a diligent resistance management program involving the rotation of products having different active ingredients.

A rotation of AiM-L™ and AiM-A Abamectin™ VetCaps — each having a different mode of action — allows the VetGun to play a significant role in horn fly resistance management.

AiM-L VetCaps are gelatin capsules containing lambda-cyhalothrin (a pyrethroid), an Environmental Protection Agency (EPA)-registered topical insecticide proven effective for control of horn flies and lice on beef cattle.

AiM-A VetCaps are gelatin capsules containing abamectin (a macrocyclic lactone in the avermectin family), an Environmental Protection Agency (EPA)-registered insecticide for effective control of horn flies on beef cattle and non-lactating dairy cattle.

Treatment and product rotation considerations

The economic threshold of horn flies on cattle is 200 flies per animal. Waiting until flies reach this number can reduce the number of treatments and is cost effective.

Late-season treatments reduce over-winter fly populations. A late-season treatment limits the number adults laying eggs that become overwintering pupa.

Rotate between chemical classes. It's not enough to simply change brands — be sure to look for different chemical classes with different modes of action. It is best practice to consider a complete pest management program.

Horn fly and lice management program

The following is a sample rotation schedule of how AiM-L and AiM-A VetCaps could be used for control of horn fly and lice if first treatment of the season is with ivermectin.

Step 1: Treat with AiM-L when flies start to appear

Step 2: Treat with AiM-A when flies approach approximately 200/animal

Step 3: Treat with AiM-L four weeks after AiM-A treatment

Step 4: Treat with AiM-A when flies approach approximately 200/animal

During winter and early spring, treat with 2x AiM-L two weeks apart to control lice. 

Before use read entire label for instructions, precautions and warnings.

Vet Gun Rotation Chart Final

For for more information on the VetGun products or for technical assistance contact us at 1 (800) 542-8916.