Last week, while conducting fly counts on pastures with beef cattle, I observed alarmingly high populations of face and horn flies on some of the animals. The action threshold for face flies is 10/face, but in some cases, there were more than 100 per animal. For horn flies, the threshold is 100 per side for beef cattle and 50 per side for dairy cattle; however, some cattle had well over the action threshold for horn flies.

Face Flies on Cattle

Horn Flies on Cattle

Horn flies typically reside on the back and sides of the cattle but move to the belly when it is very hot to escape the heat. Face flies are primarily found on the face of the cattle and are about double the size of horn flies. Horn flies can take up to 20-30 blood meals daily, causing extreme stress to the cattle. Face flies feed on secretions around the eyes and nose, as well as wounds and areas where biting flies have left openings.

To provide some perspective, there are approximately 75 horn flies within an 8-inch by 8-inch area on the animal. This indicates a significantly larger number of flies on the entire cow.

Depending on your management preferences, there are several options available to help control the fly populations:

• Dust Bags: Effective for applying insecticides as cattle pass under them.
• Back Rubbers and Oilers: Provide continuous insecticide application as cattle rub against them.
• Pour-ons: Easy to apply directly onto the cattle’s back.
• Insecticide Ear Tags: Long-lasting option that provides sustained fly control.
• Compressed Air Application (Vet Gun): Allows precise application of insecticides from a distance.
• Walk-Through Trap: Non-chemical option that physically removes flies as cattle pass through.
• CowVac: Sucks flies off the cattle as they pass through a chute.
• Oral Larvicides: Added to feed to prevent fly larvae from developing.

To find an insecticide, please use the following search engine: Veterinary Entomology Insecticide Search. Make sure to select NY to find the type of insecticide needed.

Each of these methods has its own advantages and can be selected based on your specific needs and preferences.