Population Guide: Dairy How Many Is Too Many? An effective
control program keeps horn fly levels to fewer than 50 per
animal. This at-a-glance-guide will help you easily evaluate the
effect that horn flies currently have on your herd. Keep these
other assessment tips in mind, too. - The horn fly is charcoal
gray and approximately five millimeters long (half the size of a
typical house fly). - Adult horn flies are located on the backs
of cattle, often clustering on the midline and spreading down
the sides. Sometimes, they settle around the base of cattle
horns. When the weather is hot, they may move onto the animals'
undersides. - It's easiest to make the most accurate estimate in
the morning, when horn flies are on the upper sides of the cows.
|Average to Below||Unacceptable|