03/06/2026
Blowflies are one of the most widespread ectoparasites affecting sheep in the UK, with surveys suggesting 80% of flocks will have one or more cases of blowfly strike every year.
Estimates of the number of sheep struck each year range from 500,000 to 700,000 with mortality rates of 2-3% (10,000-20,000 sheep per annum). The extent of blowfly strikes varies hugely from year to year, mainly due to weather conditions. Failure to treat a strike promptly will lead to reduced performance, secondary infections and, in severe cases, death.
There are essentially three types of topical product recommended to sheep farmers for blowfly control.
🪰-Insect growth regulators (IGRs). These products allow the female blowfly to lay her eggs but then prevent the larvae developing, stopping the lifecycle. They prevent strike for eight to 19 weeks depending on the product used. They do not treat an existing strike.
-🪰Cypermethrins. These products will treat an existing strike and give protection from further strikes for six to 10 weeks, depending on the product.
-🪰Deltamethrin. These products only treat an existing strike.
Speak to us for more information about protecting your flock and the options available.