Flystrike Prevention in Canterbury Sheep
Posted in: Sheep Services
Flystrike costs the New Zealand sheep industry heavily every year, and the losses are rarely just the sheep you find struck. Lost growth, dagging, extra labour and repeat treatment all sit behind the obvious cases.
Prevention is far cheaper than treatment, and it starts with knowing when your risk is climbing rather than reacting when you find the first struck ewe.
When Flystrike Risk Rises
Blowflies become active as conditions warm and stay active through the risk season. Strike happens when flies lay eggs on a sheep and the maggots feed on the skin, and anything that makes a sheep more attractive to flies raises the risk: dags, scouring, wounds, fleece rot after wet weather, and urine staining.
Warm, humid conditions with moisture in the wool are the classic combination. Canterbury farms vary, and properties with shelter, heavier country or a wet spring tend to see pressure earlier.
Reducing the Conditions Flies Look For
- Crutching and dagging, to remove the soiled wool that attracts flies
- Worm control, because scouring sheep are struck sheep – this is where your drench programme and your flystrike programme meet
- Shearing timing, since fleece length affects both susceptibility and how long a prevention product lasts
- Wound management at tailing, shearing and other injuries
- Dead stock removal, which cuts the fly population you are farming against
Prevention Products and Planning
Prevention products differ in how long they protect for, how they are applied, and what withholding periods apply. The right choice depends on when your stock will be sold or shorn, whether they are being retained, and your farm’s history.
Finding and Treating a Struck Sheep
Struck sheep often separate from the mob, appear restless, stamp their feet, twitch the tail or try to bite at the affected area. The wool over the site may look discoloured or damp, and there is usually a distinctive smell.
Prompt treatment matters. Sheep die from flystrike, and the ones that survive lose condition. If you are finding multiple strikes, treat it as a signal to review the whole programme rather than dealing with it case by case.
Talk to Our Sheep Vets
If you want to review your flystrike programme, plan product choice around your shearing and sale dates, or get supplies ordered ahead of the season, give your nearest clinic a call.
Timaru 03 687 9378 · Geraldine 03 693 1163 · Fairlie 03 685 8407
Frequently Asked Questions
What causes flystrike in sheep?
Blowflies lay eggs on a sheep, usually where the wool is soiled, damp or damaged, and the maggots feed on the skin. Most strike happens around the breech, but it can also occur on the shoulder. Dags, scouring, wounds, fleece rot and urine staining all make a sheep more attractive to flies.
How do I know if a sheep has flystrike?
Struck sheep often separate from the mob, appear restless, stamp their feet, twitch the tail or bite at the affected area. The wool over the site may be discoloured or damp and there is usually a distinctive smell.
How can I reduce flystrike risk on my farm?
Reduce the conditions flies look for: crutch and dag to remove soiled wool, keep worms under control so sheep aren’t scouring, time shearing well, manage wounds at tailing and shearing, and remove dead stock. Prevention products sit alongside this, chosen around when your stock will be sold or shorn.
Does worm control affect flystrike risk?
Yes, directly. Scouring sheep carry dags, and dags attract flies. A worm programme that keeps sheep clean is part of your flystrike prevention, which is why the two are best planned together rather than separately.
Can flies become resistant to prevention products?
Yes. Fly resistance is a growing problem in New Zealand. Planning which products to use and assessing efficacy is important in managing this situation.
When should I start flystrike prevention in Canterbury?
Risk builds as conditions warm and varies considerably between properties depending on shelter, country and how wet the season has been. It is worth planning with your vet against your own shearing and sale dates rather than working to a fixed calendar.