Livestock Management RANCHING
Horn Flies Are Profi t-Robbing Pests Control tips help producers take back lost gains
O
NE OF THE MOST ECONOMICALLY DEVASTATING THREATS to beef cattle measures about the size of a pencil eraser — the horn fl y.
“Even though horn fl ies are small pests, they can
be a big problem,” says Roger Winter, D.V.M., technical services veterinarian for AgriLabs. “According to the USDA, the detrimental impact of horn fl ies is more than $1 billion per year in the U.S., with up to $60 million dollars spent on insecticidal control. Financial loss can be attributed to reduction in weight gains, feed effi ciency and milk yields as well as loss of blood and energy used trying to dislodge fl ies.”
Blood loss equals lost gains Horn fl ies take anywhere from 25 to 38 blood meals
per day and with large numbers feeding on an indi- vidual animal. This can result in a signifi cant amount of blood loss each day. Unlike most other fl ies, horn fl ies remain on the host animals constantly and leave only for a brief period to lay eggs on very fresh manure. “Horn fl ies have a piercing-sucking mouth part that
52 The Cattleman July 2014
is similar to a mosquito but is more painful because it’s larger,” says Bob Pennington, M.S., consulting vet- erinary entomologist for SmartVet. “Hundreds of fl ies, each biting around 30 times a day, can result in up to one-third of a liter of blood lost per animal, per day. That’s a considerable amount of energy loss.” Conservative fi gures from research studies show
horn fl ies can result in one-tenth to one-third of a pound reduction in weight gains per calf, per day. For example, in a 5-month period (150 days), that equals 15 to 50 pounds reduction in weaning weights. At approximately $1.60 per pound, a 30-pound
weight reduction results in an average income loss of $48 per head due to horn fl ies. If a producer has 50 head of cattle, that equals $2,400 total income loss, and for 100 head it’s $4,800.
When to treat “Instead of feeding regularly, cows are fi ghting the
awful bite from horn fl ies by switching their tails, throwing their heads, kicking and stomping to dislodge
thecattlemanmagazine.com
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