Experts advise that preventive action against blowfly strike must be considered even after the unseasonal weather. As temperatures rise above 9°C, overwintered blowfly larvae start to develop and eventually pupate, so the start of the strike season will not be far behind. Blowfly strike can be easily prevented through the use of products which contain insect growth regulators (IGRs).
People talk about climate warming but the main issue farmers need to deal with is climate variation. In 2012 we witnessed a very early spring whereas this year it was extremely late. As a result, getting the timing right for treatment of ewes and lambs against blowfly strike can be extremely difficult - due to the unpredictability of the weather. What we do know, however, is that when the weather warms up so does the incidence of blowfly strike. Recent research shows that a 3°C increase in average seasonal temperature would be expected to approximately double the frequency of strike in lambs and lead to four times more strike in ewes.
As soon as the temperature rises above 9°C, blowfly larvae, that have overwintered in the soil, start to develop and eventually pupate, so the start of the strike season is not far behind. Farmers, must therefore start to plan their preventative measures, because once the adult flies are on the wing blowfly strike happens extremely quickly. The larvae can mature in as little as 2 to 3 days after the eggs are deposited in the fleece of a susceptible sheep. If an infestation is missed the reality is that a sheep can die from repeated strikes within 1 - 2 weeks.
Fiona Anderson, vet at Novartis Animal comments: "Blowfly strike occurs on over 80 per cent of sheep farms. If untreated it can severely affect the welfare of infested sheep, and may result in death. Prevention is always best because adult flies can lay so many eggs on a flock and farmers do not have the time to check their sheep. Blowfly strike can be easily prevented through the use of products which contain insect growth regulators (IGRs). These prevent the development of the damaging second and third stage maggots which are responsible for causing fly strike and stock damage."
1. Body strike - flies are attracted to sheep by the odours of excessive 'sweating' and decaying organic matter in the fleece, anywhere over the loins, shoulders, flanks, neck, back, throat or abdomen
2. Breech strike - flies are attracted to fleece contaminated with urine and/or faeces; it's particularly associated with scouring
3. Wound strike - flies can be attracted to open wounds
If left untreated, blowfly strike can adversely affect the welfare of the animal, or even cause death Productivity is also reduced if blowfly strike is present, by reducing reproductive potential and lamb crops, increasing time to market for lambs, downgrading of the wool clip, and reducing leather quality.
Speak to us at the practice if you have any questions on how best to prevent this costly disease.
In the meantime we hope the downloadable leaflet from Novartis will provide you with more information.
You can also watch the coverage on ITV news recently, with Tom on farm to discuss preventative action.