The impact of flystrike on Tasman sheep

While flies may be a nuisance in the household, their impact on agriculture, particularly on Tasman sheep, is significant.

Flystrike affects many sheep during spring, summer, and autumn, especially in humid conditions. Flystrike occurs when blowflies lay eggs in warm, moist areas on sheep, which hatch into maggots that invade the animal.

“Flystrike can move fast. If conditions are warm and humid, a sheep can become very unwell within 24 hours,” says Brent Hodgkinson, a sheep and beef farmer from the Tadmor Valley in Tapawera.

As the maggot’s hatch, they consume the sheep’s skin and muscle tissue, releasing toxins that spread throughout the body and attract more flies, worsening the problem.

“This is why prevention is so important,” Brent emphasises. “Flystrike is much easier to treat as a preventative and is avoidable with proper treatment.”

Early signs of flystrike include irritation, such as tail twitching, stomping, and rubbing or biting at the affected area. This is followed by shade-seeking behaviour, loss of appetite, and signs of depression. Some sheep may not show symptoms until significant damage has occurred, leading to wool loss, skin blackening, foul odours, and visible maggots.

“Shearing is often key,” explains Brent. “Blowflies prefer to lay eggs in the fleece on the skin, so shearing the sheep removes cover for the maggots to develop. This generally prevents flystrike for about three weeks minimum, when a preventative flystrike treatment should be applied.

He stresses the importance of applying preventative flystrike treatments before the risk period.

Proper timing and product application are crucial in preventing flystrike. Brent mentions several methods, including dips and spray treatments, suitable for both large flocks and individual animals, offering protection for up to ten weeks, influenced by factors like rainfall and the application method. A standard garden knapsack or sprayer is effective for applying these treatments.

“It’s essential to treat sheep when they’re dry, as rain can dilute the treatment, reducing its effectiveness,” Brent adds.

Additionally, managing worm levels helps reduce diarrhea and lessens smell and dags, which can attract flies.

Flystrike causes significant pain to the animal and is a significant welfare concern, as outlined in New Zealand’s Animal Welfare Act 1999. Ultimately, proactive measures benefit both the animals and the animal owner.