2020 Blowfly Alert

According to NADIS the UK is now at High or Severe risk of fly strike.

Last update 15th July: A large and growing blowfly population and warm wet summer weather create the perfect recipe for high fly risk, particularly for lambs. Early in the year most strikes occur around the back end of sheep - but as the season progresses the risk of body strike grows - so care is needed to look out for the early signs and treat it quickly.

In the UK, strike is caused primarily by the green bottle fly, Lucilia, which seeks decomposing matter to lay her eggs. Carcasses, dirty backends, foot rot lesions and open wounds are all good candidates for egg laying sites.Blowfly strike has a serious impact on the welfare of sheep within the UK, as well as having a major impact on productivity. Figures from 2015 suggests blowfly strike costs the sheep industry £2.2 million per year.

Losses are incurred from:


  • Loss in productivity (weight loss and decreased milk yield)
  • Fleece damage
  • Deaths
  • Treatment costs; including product, labour and time

Flocks should be carefully checked at least once a day throughout the blowfly season to look for any signs of blowfly strike. It is often necessary to handle animals and part the fleece to fully appreciate the extent of disease.

Early signs of strike

  • Irritation
  • Nibbling at tail head
  • Increased swishing of tails
  • Rubbing
  • Further signs of discomfort in lame animals

Signs of Severe Strike

  • Discoloured/damp fleece
  • Fleece loss
  • Separation from flock
  • Sick animals
  • Death (due septicaemia from secondary bacterial infection and release of toxins)

To prevent Blowfly strike, the following steps are recommended:

Discuss with your vet or SQP the most appropriate product, based on labour resources, age of your lambs during the risk period, withdrawal periods and anticipated slaughter dates

  • Reduce dirty backends - Dagging, crutching and timely shearing are all important.
  • Tail docking lambs is a debated but accepted procedure to reduce strike in lowland flocks.
  • Control worm burdens. Discuss with your vet an appropriate faecal egg counting and parasite control plan.
  • Treat lame sheep promptly. Flies are attracted to wounds caused by footrot.
  • Manage the fly population: Reducing the fly population early in the year has the greatest impact on the fly challenge during the grazing season

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24th July 2020

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