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South Australia worms, flies and lice update - March 2019

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides





Adelaide: Colin Trengove, Sheep Health Lecturer (UA Roseworthy campus) (

Not unexpectedly for this time of year, the long hot dry continues, and the outlook is for a delayed autumn break with below average rainfall. With an El Niño weather pattern in place, 2019 is not promising much, but we can still hope for un-forecasted low pressure systems to emerge from the west and contradict the unreliable long range forecasting at this time of year.

What is predictable is that worms pay no attention to weather forecasts and it is surprising to see that over half of the 65 Worm Egg Count (WEC) submissions in the last month have indicated a need for a drench despite negligible rainfall since mid-December. Perhaps less drenching has occurred due to the parched conditions, and recent WEC monitoring is simply highlighting the significant carryover of worm burdens from last year.

Autumn lambing will soon be underway and I suspect many flocks will be receiving a pre-lambing drench. Recent worm egg counting would support this, but general observations are no replacement for specific monitoring in terms of drenching needs. Another potential pre-lambing preventative treatment is a Vitamin ADE injection given the lack of green feed this year. Other significant current health risks are pregnancy toxaemia (twin lamb disease) and milk fever given that most pregnant ewes will be dependent on grain to meet their rising energy, protein and calcium needs with the onset of lambing.

The extended dry conditions combined with autumn shearing means that flies have been less of a concern in recent months. However, they are an ever-present risk especially with sheep on a grain-dominant diet increasing the risk of scours due to ruminal acidosis. Pizzle strike is also a risk depending on the timing of shearing and/or crutching.

Lice receive scant reporting attention, but most producers continue to routinely treat at shearing given the fear of contracting lice infestations from neighbouring flocks. The steady demand and value of wool also heightens the desire to minimise losses due to lousy wool clips. 

For March 2019 state outlooks, please follow the links below:
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