By: Rebecca Konopka
Carter County Extension Agent
Each summer, pastured cattle must deal with an annoying pest – the horn fly. These flies use their piercing-sucking mouthparts to take up to 30 blood meals from their host each day. This incessant feeding schedule and their large populations can severely impact growing calves and lactating cows.
Horn flies can also play a role in transmitting disease. In all, horn flies suck about $1 billion in weight gain/milk production losses and control costs each season.
The close relationship between cattle and horn flies can help with control. The flies leave the animal to lay eggs in fresh cow manure or to change hosts. Consequently, most application methods will expose flies to insecticide residues. These include forced-use dust bags or back rubbers, insecticidal ear tags, sprays and pour-on formulations.
One of the biggest challenges in horn fly control is rapid development of insecticide resistance and there are no clear-cut strategies that solve the problem.
Producers can do a several things to manage resistance:
- Do not treat for horn flies until numbers exceed 200 per animal. Cattle can tolerate up to this level before economic losses occur.
- If feasible, keep growing calves and lactating cows separated from mature stock. Fly reduction on growing and lactating animals is more likely to provide an economic return.
- Use periodic treatments with insecticides that have other modes of action (organophosphates, etc.) to break fly exposure to a single product group. Rotating products with different modes of action is a basic strategy that may reduce the potential for resistance.
- Remove ear tags in fall to reduce horn fly exposure to low concentrations of pyrethroids.
- Use a late-season application to reduce the number of horn flies that will enter the over-wintering stage on the farm.
If you don’t notice significant fly reduction within two weeks of applying tags, it’s a good indication resistant flies are present.
For more information contact the Carter County Extension Office. Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of economic or social status and will not discriminate on the basis of race, color, ethnic origin, national origin, creed, religion, political belief, sex, sexual orientation, gender identity, gender expression, pregnancy, marital status, genetic information, age, veteran status, or physical or mental disability.
- The Grayson Farmer’s Market is open on Saturdays from 9:00 AM until sell out. The market is located in the shed behind the Extension Office. The Olive Hill Farmer’s Market is open on Saturdays and Wednesdays at 8:00 AM and Mondays at 3:00 PM until sell out each day. The Olive Hill market is located in the Save-a-Lot parking lot.
- Hay sampling is underway now for the East KY Hay Contest. Call 474-6686 by September 19th to request sampling.
- Hike & Learn – Friday, August 19th at 9:00 AM – Greenbo Lake State Resort Park Fern Valley Trail – Meet at the picnic tables in the lodge parking lot that are to the left of the main entrance.
- Honey Extraction Demo – Monday, August 22nd at 10:00 AM – Carter County Extension Office
- Extension District Board – Tuesday, August 23rd at 9:00 AM – Carter County Extension Office