Horn flies will soon be bothering cattle. The best way to give the animals some relief from horn flies is to use several different control methods, say Janet Knodel, North Dakota State University Extension entomologist, and Greg Lardy, NDSU animal science department head.
Control methods include insecticide ear tags, self-application devices (dust bags or oilers), pour-on or whole-body insecticide sprays, feed additives and non-chemical walk-through traps.
Insecticide ear tags contain a synthetic pyrethroid or organophosphate. As the animal moves, the insecticide is released to the surface of the tag and contacts the cattle’s hair.
Dust bags and back rubbers are available for cattle to treat themselves. Provide enough bags for all of the animals in a herd because bulls and older cows tend to dominate bags.
Pour-on, whole-body sprays or duster insecticides can be applied, but handling the animals can stress them. The products only have a short residual. When fly populations are high, combine strategies, Knodel suggests. Use ear tags early in the season and whole-body sprays later in the season.
Feed additives containing an insecticide can kill 80% to 90% of the fly larvae. The insecticide passes through the animal’s digestive system and will spread through the manure where the fly maggots are found. These additives act as an insect growth regulator and prevent the fly maggot from maturing into an adult.
One disadvantage of feed additives is that flies can migrate from untreated herds. To avoid the development of insecticide resistance, don’t place ear tags on cattle until horn flies are present, remove tags in the fall after a frost and rotate the insecticide classes in the tags annually.
Research shows that nonchemical walk-through traps can help reduce horn fly numbers by as much as 50%. Traps can be set up to require cattle to pass through them to obtain water or to access salt.
As the cattle pass, a canvas brushes their backs, disturbing the flies. The flies are attracted to the light at the top of the trap and fly upward into an inverted cone. Once in the cone, they are unable to escape. Research is under way on additional fly control methods, including fly traps with sex attractants, and releases of sterile male flies and predatory wasps or dung beetles.
Source: NDSU Extension Communications
This article published in the July, 2011 edition of DAKOTA FARMER.
All rights reserved. Copyright Farm Progress Cos. 2011.