Flystrike is the second most costly disease that affects sheep after gastrointestinal parasites. The severity of the problem varies between years, depending on rainfall, but it is a problem in weaners in most years. Flystrike control and prevention are based on integrating management to reduce sheep attractiveness to fly strike, long-term genetic selection for less wrinkly breeches, strategic jetting in the high-risk period and using fly biology to minimise fly numbers.
All aspects of management are important to control flies to reduce production losses whilst maintaining sheep wellbeing. Strategic management to minimise chemical use is important to reduce the risk of chemical residues as well as reducing the risk of developing resistance.
Reduce the attractiveness of sheep to flies
Correct tail length and mulesing technique
Dock lambs at the third palpable joint of the tail and use the modified mules as indicated in guidelines from the National Mulesing Accreditation Program. All mulesing contractors and sheep producers mulesing their own sheep must undergo training for mulesing. Lambs to be sold for slaughter should not be mulesed but docked with the correct tail length. Research shows that Border Leicester x Merino ewes used for lamb production are at much lower risk of flystrike when mulesed. Extensive research by AWI is investigating alternatives to mulesing.
Timing of crutching and shearing
Time of shearing has a major effect on the risk of flystrike. Shearing just before the major fly risk time will reduce the need for jetting to prevent flystrike and supervision for flystrike. In addition, crutching before the major fly risk period will prevent breech strike for a few months, especially if sheep are scouring and have dags. Avoid excessive crutch size as there is no reduction in risk of flystrike compared with moderate crutch size. A large crutch will reduce fleece values by at least 50 cents/head.
Control worms to prevent scouring
Scouring is a major risk factor for flystrike. Effective worm control will reduce the risk of breech strike.
Selecting sheep for reduced susceptibility to body and breech strike
Selecting sheep for low dag score is heritable and, over time, will help reduce scouring. Selecting for low WEC will reduce worm contamination on pasture and in the longer term, help control worms. Selecting for low breech wrinkle also leads to larger breech bare area. Selecting sheep with less fleece rot will also reduce the risk of body strike.
Strategic application of chemicals to prevent flystrike
Jetting to prevent flystrike is an important strategy to prevent body and breech strike during high risk periods. This is especially important when flock supervision is limited. Choice of product needs to be based on length of protection, efficacy, withholding periods for wool and meat and cost. Effective jetting equipment and correct technique are important to ensure that the chemical provides long-term protection.
Other strategies to control flystrike
Strategies to control fly numbers have limited value. Lucitraps® can reduce the fly population substantially (by up to 50%). However, this does not necessarily lead to less jetting and needs to be adopted on a regional basis to be of any value. Fly traps can be useful to monitor fly numbers. Some evidence also indicates that the risk of flystrike varies between paddocks, so running highrisk
sheep in low-risk paddocks should be of some value.
