Awareness and prevention of flystrike in sheep
The blowfly season is lengthening alongside an earlier emergence of flies,听largely due to听changing weather patterns. The changing climate means that is it important that farmers stay vigilant as blowfly season becomes increasingly challenging.听Recent wet weather followed by warmer, humid conditions will significantly increase the risk of strike.听听
Blowflies are one of the most widespread ectoparasites affecting all ages of sheep. This high prevalence means that听nearly all听flocks are at risk of blowfly听strike听and it is听estimated听that听blowfly听strike costs the UK sheep industry millions of pounds听each year.听听
Control of fly strike requires good management, in combination with preventative products as by the time that strike is visible, animal welfare and performance are already听comprised.听听
Blowfly听life听cycle听
The blowfly overwinters in the soil as a pupa, until soil temperatures reach 9-10掳C听when the pupa听emerges听as an adult fly, and then lay eggs on their host e.g. a lamb with a dirty backside. Adult females lay eggs in batches of up to ~200 eggs at a time.听These eggs then hatch after 12 hours and live on the host for up to three days feeding as maggots rapidly damaging the skin and underlying tissue before crawling away and dropping off the sheep and pupating in the soil.听When a sheep has multiple infestations e.g.听numerous听flies laying eggs, a wound is quickly created, and the odour is attractive to other flies.听听
Typical blowfly season is from spring to autumn; however,听changing weather patterns and rising temperatures has resulted in some areas reporting blowfly strike beginning in March and lasting through to November.听听
The Impact of听flystrike听
Blowfly strike is detrimental to the welfare of ewes and lambs as well as being a major economic concern for farmers. Flystrike results in reduced productivity, lower听fertility听and weight gain. Lamb growth rates are reduced resulting in longer finishing times resulting in lambs being kept on farm for longer, increasing competition for grazing and grass for ewes. Ewe body condition is affected with weight loss following flystrike contributing in a delay to in ewes reaching target body condition for tupping. Loss of body condition also has the potential to听impact听fertility.听听
Managing and听preventing听flystrike听听
Prevention is key to enabling better control and flock protection therefore it is important to reduce the opportunity for flies to lay their eggs.听
- Flock听health听-听Implement a worming strategy to reduce dirty backends and soiled dirty fleeces which are attractive to flies. Also ensure that foot infections听e.g.听footrot听and wounds from damaged horns are treated.听听
- Fleece听management 鈥撎�Ensure听timely听clipping of ewes and any wounds from clipping have been treated.听听
- Deadstock听management 鈥撎�Carcasses attract flies. Ensure that deadstock is removed promptly and covered before collection.听听
- Preventative Treatments 鈥撎�Use a preventative pour-on early in the season. Treating early to prevent flies from the first generation multiplying helps to reduce the risk as the season progresses.听听
- Monitor Blowfly Emergence 鈥撎�The听 can help to predict when blowfly emergence can be expected. Actual timing will vary across farms however the forecast can help听identify听risk periods. Currently the forecast now听indicates听full emergence across Scotland.听听听
The potential for rapid escalation in fly numbers听as numbers are about to reach their peak, alongside our changing climate means that extended blowfly management and protection is needed across flocks.听听听
Five take听home听messages听
- Blowfly strike affects sheep of all ages.听
- Blowfly strike is听common听and听changing weather patterns mean that is it important to remain vigilant to the risk throughout the year.听
- Lamb growth rates and ewe condition and听subsequent听fertility are all negatively听impacted听by flystrike.听听
- Preventative treatment of ewes and lambs is听required听combined with good flock management to protect against flystrike.听
- Protection is becoming increasingly challenging however听the听听is great tool to help predict emergence.听听听
Jamie Houstoun,听Agricultural Consultant,听Jamie.Houstoun@sac.co.uk
Posted by SAC Conulting on 21/07/2026
