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Sheep lice are still prevalent through many districts in South Australia.  This is despite the fact that having sheep lice costs you money. Recognising the problem in your flock and implementing appropriate strategies will minimise the cost. Eradication is the only option to avoid any ongoing costs.

It may take 4 to 6 months from shearing for lice to be detected on lightly infested sheep.  So producers with early spring shorn sheep should be monitoring closely the status of flocks in order to detect any infestation.

If lice are found then a decision must be made whether to apply a long wool treatment, wait until shearing or shear early.  The decision should be made on an economic basis and will depend on various factors including: the level of infestation, the prevalence across your flock and the time until the next scheduled shearing.

The Long Wool Tool in LiceBoss can help you to decide whether it makes better economic sense to muster the sheep and apply a treatment, or to wait and treat the sheep after they are next shorn. Early shearing is generally not the most cost effective choice, but can be considered if the early shearing time is convenient and it is essential to eradicate lice immediately rather than wait until the usual shearing time.

Sheep infested with lice

Beware of the chemical withholding period on some long wool products as the time length can make their use prohibitive too close to shearing.

Don’t fight alone.  Sheep lice have been a long time issue. Individual producers may eradicate the problem however if neighbours don’t, chances are the problem will return.  Sheep lice are a community issue; work with your neighbours, stock agents, transport operators and ram suppliers. District lice action groups are showing that a little collaboration and diligence can alleviate the problem.

Producers interested in finding out more about setting up a lice action group should contact your local sheep adviser (private consultant or PIRSA).

Summer/autumn shearers should be planning post shearing treatment strategy, particularly if lice are evident now.

Plunge dipping is the best application method for eradication of sheep lice because it ensures total saturation of the fleece when done correctly.  Some key factors for effective plunge dipping include:

  • Only dip sheep between 2 to 6 weeks after shearing
  • Maintain correct chemical concentration
  • Dip length should be 9 metres minimum
  • Sheep should swim for at least 30 seconds and heads be dunked twice
  • Dunk the sheep by pushing the head backwards as well as downwards
  • Sheep difficult to wet should be given more time and attention in the dip
  • Keep the dip clean – clean out after dipping one sheep for each two litres of initial dip volume (e.g. 4000 litre dip volume – clean after 2000 sheep)

If plunge dipping is not possible then a backline treatment is recommended.  But it is essential that every sheep is treated effectively for eradication to occur and to reduce the development of resistance to the product.

Some essential tips include:

  • Only use products that have no known lice resistance.
  • Read the label instructions carefully.  Apply within 24 hours of shearing (Note: The Bayer product ‘Avenge’ is registered to be applied up to 7 days off shears).
  • Be aware that the product takes time to spread around the body so all lice are not killed immediately
  • Correct dosing is essential. Under dosing is the major cause of failure to eradicate lice. Read the label to determine the correct dose.
  • Weigh some of the heaviest sheep and set the dose for all sheep in that class to that weight
  • Use the recommended applicator for that product
  • Apply chemical from the poll all the way to the tail. READ THE LABEL.
  • Ensure sheep are cleanly shorn all over.  Backline treatments do not work effectively on sheep not closely shorn or with lumpy wool.  These sheep need to be dipped or culled.
  • Check the label for rain fastness of the chemical.

In summary, have a lice eradication plan, seek advice, communicate with your neighbours and work together.  Form a local lice action group.  Effective treatment of lice will not just happen. You have to make it happen!

Refer to the Liceboss website for more detailed information: www.liceboss.com.au