Sheep farmers are being encouraged to use Elanco’s Blowfly Forecast to track when fly populations are rising in their area, and develop a control plan, ahead of temperatures rising.

Elanco Animal Health’s ruminant technical consultant, Matt Colston, says the Forecast has been developed in collaboration with NADIS to help farmers identify periods of high blowfly strike risk for their flocks.

“Changing weather patterns mean the fly season is starting earlier and lasting longer,” says Mr Colston.

“This means farmers should be prepared to apply protection early on in the season, as preventative treatment is always the most cost-effective strategy against blowfly strike.”

He says the active season for the main species causing blowfly strike in the UK – green bottle – has lengthened, with strike occurring earlier in the spring and continuing well into the autumn.

“The Blowfly Forecast is a really useful tool for monitoring blowfly activity, which tends to start as soon as soil temperatures rise above 9°C,” adds Mr Colston.

“Once the temperature gets above this, any pupae in the soil will start to develop and the first wave of flies will emerge.”

He says blowfly strike can happen very quickly and 94% of farmers have reported being caught out by it, while 99% say it has caused them financial losses.

“Prevention is essential because by the time symptoms are visible, it’s typically too late to protect sheep, and treatment can be costly,” adds Mr Colston.

“By taking early action to tackle the first wave of flies, farmers can reduce blowfly numbers early and dramatically reduce the risk of fly strike for the whole season.”

He says Elanco’s Blowfly Forecast, which is available online at, can be used to assess risk alongside considering other factors.

These include: the location of the farm, with lowland flocks at greater risk; whether tails have been docked, with undocked sheep at greater risk; faecal soiling; whether a preventative treatment has been applied; the farm’s history of strike; and the weather, with warm and wet conditions ideal for fly strike.

“Once blowfly strike has been identified as a risk, farmers can protect their sheep by applying an Insect Growth Regulator (IGR) product, such as those in the CLiK™ range,” says Mr Colston.

The range includes: CLiK™ Extra, CLiK and CLiKZiN, which offer a scale of protection from eight to 19 weeks, with CLiKZin offering a meat withdrawal period of just seven days.

He says IGR products must be applied in the right amounts, and in the right way, to get the best results.

“I’d advise farmers to use the four-stroke application method to ensure there’s a four-inch bandwidth of product applied on the animal, taking care when lambs are small because a smaller target requires greater precision,” adds Mr Colston.

“I’d also recommend applying the product in a pen, rather than a race, and clip out dags first to make sure animals are clean before application”