Blowflies are eating into the profits
Regularly treating sheep for flystrike helps avoid the problem, but is a significant cost for woolgrowers and means a reliance on chemicals
Blowflies are eating into the profits of woolgrowers, and anything that helps get on top of the parasite is welcome. Just ask Geoff Fisken (pictured).
Mr Fisken manages a 2000-hectare family property, 'Lal Lal Estate', 20 kilometres south of Ballarat in Victoria, which runs 12,000 adult Merinos including 7000 breeding ewes. Each year humid weather triggers fly waves, creating a headache for woolgrowers.
Mr Fisken and his farm apprentice are the only labour on the property so they have an acute understanding of the extra work and costs associated with managing blowfly strike.
"We've got a number of ways of minimising the impact of flies," he says. "This includes breeding structurally sound sheep to cut body strike, mulesing lambs to reduce the breech strike in later life, shearing and crutching, managing worms and grazing to reduce scouring, and using chemicals.
"It all involves a cost to a woolgrowing business and takes time and labour. All woolgrowers are under increasing pressure to increase their labour efficiency and control their costs."
Recent warm, humid weather in the NSW Riverina have been ideal for blowflies. Ian Evans, NSW Department of Primary Industries sheep and wool officer, is based at Deniliquin and says fly waves can be particularly severe in some areas.
"In some cases we've had up to 10 per cent of flocks affected, while strike rates of three per cent can be common," he says. "The costs are significant, especially if there are sheep deaths."
Sheep blowflies are estimated to cost woolgrowers more than $280 million a year in lost production and control costs. The costs include sheep mortalities and production losses (through reduced wool cut, cotting and lower staple strength), as well as the direct costs of control (mainly treatments and labour).
And with emerging resistance to some chemical treatments, the situation has the potential to get worse.
Mr Fisken's biggest challenge from blowfly attack at 'Lal Lal Estate' comes with summer rainfall.
"We have a reasonably high summer rainfall, so we have to manage sheep worms carefully to reduce the incidence of scouring, which can make sheep vulnerable to flystrike," he says.
All lambs are mulesed to reduce the incidence of breech strike later in life, and they crutch all sheep in November and December and shear in March. "This lets us remove stain from the breech before summer and lets us backline the sheep with Vetrazin® so we can get through to shearing and fit in with the chemical withholding period.
"Treating sheep as a course of habit is helping us avoid the problem of flystrike, but it involves a cost and means we have a reliance on chemicals. It costs 25 to 30 cents a head to backline the sheep, and that doesn't include labour, but we can't leave the sheep untreated and have them become flystruck.
"I'd rather not have to mules and routinely treat sheep with chemicals, but at this stage we have no alternative.
"Any research which can help us get a better understanding of how to control blowflies has to be a good thing."
Images: Geoff Fisken: breeding structurally sound sheep, mulesing, shearing, crutching, worm management, grazing to reduce scouring and chemical treatment are all used to minimise the impact of blowflies. Photos by Jeremy Bannister
More information: Integrated parasite management.
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