Blowfly risk is still high going into the autumn and experts are worried that farmers might get caught out by the lengthening season.

Richard Wall, Professor of Zoology, Veterinary Parasitology and Ecology Group for University of Bristol, said: "Blowfly abundance is now at its seasonal maximum and the very warm weather going into September means that fly activity will be high. The dry summer probably depressed the population of g.i. nematodes on pasture and reduced the quality of grass available, so remaining lambs may be cleaner than in a wet year which will help to reduce their strike risk, but any rainfall in early September is likely to be associated with a very high risk of strike in both lambs and ewes and this will persist until cooler autumn weather prevails."

Farmers are advised to take control and strike first with preventative treatments, rather than risk impact to productivity and profits.

The National Farm Research Unit has released the results for its Elanco Blowfly Survey, based on responses from 150 British sheep farmers. The data reveals that despite strong consensus that preventative techniques are more effective than treatment (97%), there is still a high proportion of farms hit by strike each year. (79%)

Experts also identified several underestimated factors in effective blowfly management, including:

• Extended and less predictable blowfly season results in majority of farmers getting caught out – even when protected.

• The true cost of strike goes beyond treatment and is widely misunderstood.

• Environmental factors are essential when predicting strike, but only a minority regularly check reports and trackers.

Although 97% of respondents agreed that prevention, not cure, is best for blowfly strike, only 51% of farms caught out by blowfly strike have adjusted their system to incorporate treatment earlier in the year – leaving almost half of farms under protected and at risk.

A significant number of farmers find the timeframe of blowfly season increasingly difficult to predict, with 96% caught out by strike in the last five years. 82% of respondents believe the season has extended in some recent years, with significant activity being measured as early as April in many years.

Fiona Lovatt, an independent sheep veterinary consultant at Flock Health Ltd, found the low use of weather forecasts, soil and air temperature (26%, 37% and 31% respectively) to indicate a wider issue: “A lot of farmers think “it’s not in my control” because of bad weather or other circumstances. But they’re unnecessarily putting limits on themselves. By asking what they can control, what improvements can be put in place, farmers have the power to make their protection far more robust.”

Professor Wall believes that many farmers underestimate the costs caused by strike: “A ewe dying of strike represents a loss of at least two hundred pounds, factoring in replacement and vaccination costs. If you take time costs into account however, and the loss of production from reduced lamb weight gains, strike actually ends up having a much more severe financial impact on a farm than it initially seems.”

Ms Lovatt said: “Many farmers couldn’t estimate the cost of blowfly strike according to the survey. Even those who can are often not counting in loss of production, or cost of labour, despite 86% of farms experiencing a considerable loss of time due to blowfly strike. And arguably even more significant – both financially and in terms of welfare - is the effect on the future performance of an animal that has suffered strike.”