Dr. Barz: Controlling flies helps the bottom line
June 8, 2017
The recent rains were great for the pastures in our area, (eastern South Dakota) but the crop farmers are a bit frustrated. Strangely, you need to only travel a few miles from our area to reach a drought area. Many producers north of us have not gone to grass yet and some are marketing pairs while others are moving cows and calves to feed lots. Hopefully all will soon receive adequate rains and the grass will grow. As the weather warms we will undoubtedly see an increase in flies. The parasites cause irritation and pain, reduce weight gain and transmit disease. Now is the time to prepare a strategy to eliminate your problems.
There are four common fly pests in our area:
1. Face flies – these do not honestly suck blood from cattle but have sharp biting mouth parts. They damage the skin and then consume fluids and blood from the injuries to the nose and face. They also suck liquids from eye secretions. These animals spend very little time on their cattle host and travel from animal to vegetation back to another animal. The females deposit their eggs into manure pats where the immature stages develop. These animals are migratory and will travel miles to infect other herds.
2. Horn flies – These are biting insects which consume at least thirty blood meals per day. This is very stressful to the mature grazing animal. They live on the back, sides and poll of the host. Females deposit eggs into the manure pat which mature into adults in 10-20 days. Their populations usually rise during the early grazing season to very large numbers (200-30 per animal) and continue to grow throughout the grazing season.
3. Horse flies – These are very large flies which consume blood meals. After a meal the females lay their eggs on plant near ponds or streams. The populations of this insect don't become large, but their bite is very painful. Control of this pest is difficult.
4. Stable flies – We are seeing more of these flies in our area. They are generally found consuming a blood meal from the front legs of the host. Their painful bite causes cattle to bunch together, stamp their feet or stand in water. They deposit their eggs in rotting plant matter mixed with moist manure. These flies are more common in the feedlot rather than pasture. One innovative method of control is parasitic wasps. They are predators of the flies immature stages and are non-stinging which causes no problems to humans or livestock.
Control of the flies is a complex issue for your herd. You must estimate your problems from previous years and identify the type of fly causing the problems. I agree that most infections are a mixtures of insect species, and there is some crossover in treatment. The life cycle of the fly should help you select proper treatments. We cannot totally eliminate all flies, but decreasing populations helps increase livestock comfort.
Most controls involve chemicals.
• Injection with prolonged release paraciticide
• Sterilization of the manure pat with feeding of special mineral
• Pour-ons with residuals result in about three weeks of control
• Sprays and misters usually require weekly usage during peak populations
• Fly tags are effective for horn flies.
• Dust bags and backrubbers allow daily self-treatment for the animal.
Insects develop resistance to these chemicals over time and rotation is needed to increase efficiency. Sanitation is the back bone of control around the farmstead or feedlot in addition to chemical control. Baits and premise sprays are useful in confinement areas.
Flies are a common problem during summer. They irritate the host cow and decrease production. Consult with your veterinarian, extension specialist or nutritionalist and develop a ranch specific program to increase your herd's comfort. It will increase productivity and improve your financial return.