With warmer days and longer evenings announcing the arrival of summer and good silage weather, most stock owners do not need reminding of the problems that they may face from now until well into the autumn. Across the country, the fly is a cause of concern for all farmers; whether the main enterprise is sheep, dairy or beef. 

Changing weather patterns, however, have meant that it is now not uncommon to hear of cases as early as April and as late as October. Blowfly strike can occur quickly, and with devastating results, in warm, humid weather and despite being an annual problem, and entirely preventable, over 90% of farmers have been caught out by blowfly strike in the past. 

Understanding the blowfly life cycle The lifecycle is so quick when environmental conditions are right, and the volume of maggots is so high, that significant damage from blowfly strike can occur in as little as 24-36 hours after egg-laying. Understanding the blowfly lifecycle helps to understand the importance of a truly preventative approach. 

Soil temperatures above 9 degrees celcius are needed for the fly larvae overwintering as pupae to mature and emerge as the ‘first wave’ of flies. 

Female flies are attracted by the odour of wounds, soiled fleece or dead animals and will deposit many hundreds of eggs onto affected sheep. 

These eggs will then hatch into larvae and, as they progress to stage 2 and 3 larvae, they feed on the sheep’s skin causing wounds – or ‘blowfly strike’ (myiasis). 

Whilst the blowfly (Lucillia sericata) is primarily responsible, once the initial strike has occurred, other species can escalate the problem by laying their eggs in the same site: this is called ‘secondary strike’. 

In warm, wet weather significant damage can occur in as little as 36 hours after egg laying. The areas most prone to damage are the withers, flanks and the tail area, particularly after scouring. Open wounds are particularly vulnerable. 

After three days the mature larvae drop off the sheep and pupate in the soil, giving rise to more blowflies. Successive waves of blowfly then emerge throughout the summer with numbers increasing with each occurrence. 

Beware the Blowfly! 

The symptoms of blowfly strike range from 

agitation – foot stamping, vigorous shaking, 

gnawing or rubbing of the tail and breech – to 

dejection and ultimately death. However, by the 

time strike becomes visible a considerable 

amount of damage will already have occurred 

and farmers spend a lot of time checking for, 

and worrying about, blowfly strike. 

If the conditions are right for blowflies to lay 

their eggs one case of strike may mean other 

animals have been struck or are susceptible to 

strike, so in a few days one case of strike can 

escalate to multiple animals. 

Understanding the Implications of Blowfly 

Blowfly strike is not only a major welfare issue, but one that requires stressful and time-consuming treatment. The financial implications of treating can be very costly, dealing a heavy blow to farm margins. 

Average costs of blowfly strike: 

£80 – average loss per lamb that dies from strike; 

£10 – production loss per struck lamb; 

£10 – labour cost to handle each struck animal; 

50p – cost of treatment per animal; 

£200 – the approximate cost of breeding a replacement ewe. 

Prevention is the best form of control… 

for flock health, financial security; and for peace of mind. The key aim is to reduce both the number of susceptible sheep and the number of flies in the environment. If strike does occur, you must be quick to act with an SP pour-on such as cypermethrin or an OP dip to minimise distress, prevent production losses and even the death of affected animals. 

Ongoing strike prevention should then be applied using an IGR (Insect Growth Regulator) for the rest of the flock, if they have not already been affected. If you are concerned about blowfly strike or parasitic 

management please speak to one of our vets or 

RAMA’s who will be happy to help. 


Elanco survey via NSA of 130 sheep farmers, April 2016. 

Richard Wall and Fiona Lovatt (2015). Blowfly strike: biology, epidemiology and control, In Practice 37:181- 

188 doi:10.1136/inp.h1434. 

.Bimeda Animal Health

Its our Birthday!

To mark the occasion we would like to invite you to celebrate with us at Woolsery Show (25th July), North Devon Show (3rd August) & Holsworthy Show (25th August). We would love to welcome you at our stand and raise a glass to the past 10 years and look forward to the next! 

Fantastic Farm Walks

The first of our farm walks was held on April 14th by kind permission of the Pomeroy family at Wedfield Farm. Working in partnership with Harpers Feeds & Zoetis we were joined by over 100 guests. 

Following an introduction to their farm by the Pomeroy family we split into 4 discussion groups that rotated after each talk. 

Torch Vet Emily Linton discussed Monitoring & Managing for successful heifer rearing focusing on working with your farm vet to find out how your calves and replacement heifers are performing currently, setting targets for what you want to achieve & monitoring to ensure these targets are met. 

Sophia Elworthy presented on Genomics where discussions were held to decide which heifers are best to breed from, best bull choices and how to decide what to sell when you have surplus. The synchronisation talk by Steph Prior & Andy Tyrer from Zoetis looked at the importance of age at first calving which incited a lively debate. Our final group was Ian Waters and Richard Watson speaking about feeding dairy replacements to achieve 24 months calving.  

Our second event was held at Lower Twitchen Farm in the 

sunshine where we were welcomed by hosts Bernie & Jason Worth. 

A smaller group enabled lively debates & plenty of questions as the topics were discussed in rotation. Jenny Hookway spoke of the benefits of our Youngstock Club & explained how to join. 

On both days our farm team were on hand giving Client’s a chance to discuss the day’s subjects and allowed an informal opportunity to talk. It was great to see Clients talking and sharing information especially after Covid restrictions. 

We will be holding further events in the near future and look forward to welcoming you. Keep an eye on our social media for the latest updates! 

Time to upskill? Every Torch Vets FarmSkills course is designed to be of real and measurable benefit. After all, time away from the 

farm needs to be well spent. That is why we offer a diverse programme to meet your needs wherever you farm and whatever your level of experience. 

We are currently planning Mastitis, calf rearing, AI & Herdsperson courses so if you are interested please email charlottepardon@torchvets.com and we can add you to our list! 

The Sustainable Control of Parasites 

Sheep (SCOPS) group is continuing to offer its Nematodirus Forecast at no charge, providing a vital service for sheep farmers, vets and advisers to protect the health of lambs born this spring. The forecast predicts the hatch date for Nematodirus based on temperature data from 140 weather stations throughout the UK and should be used in combination with your grazing history to assess the risk of Nematodirus infection in your lambs. 

Check it out at