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South Australia worms, flies and lice update - July 2018

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides





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

Farmers have reverted to talking about rainfall in points so that it can be more easily quantified, and it also sounds better! That said there has been a green tinge across most of the State since the start of this month. In contrast, the season in the south east and Adelaide hills has been good to exceptional.

Monitoring over the past two months reflects rainfall with relatively low counts in the upper half of the State and generally moderate to high counts in the south east. The long dry autumn/early winter has limited worm larvae pickup and worm egg counts have been mostly low in dry and lactating ewes. Whereas producers in the south east are well advised to monitor stock to ascertain the need for a drench both pre-weaning and before summer.

Lambs rarely need a drench at marking with the possible exception of years such as this where they have been forced to fossick for feed more than usual. Ewe milk supplies are likely to have dwindled similar to grain and hay supply, and the risk of lambs acquiring a worm burden is correspondingly increased.

There have been many sorry tales of ewes going down in the lead up to lambing with pregnancy toxaemia due to progressive starvation when energy is most needed. In addition, there are similar stories of ewes walking away from lambs as they are too weak to mother up. This is obviously unintentional but reflects the lack of appreciation for the amount of energy required to support developing foetuses, and hay alone and/or scant dry feed does not supply sufficient energy to meet these needs. Current and foreseeable meat and wool prices mean prolonged supplementary feeding of sheep is still very profitable despite the cost of grain/pellets but supply and awareness of the amount required has been limiting.

As weaning approaches, a worm egg count is useful to assess the worm burden in lambs and potentially the option to assess which worm drenches are effective in your flock. A worm egg count of 250 eggs per gram or more is desirable to achieve a reliable drench test result. It is recommended that a drench resistance test be conducted at least every 3 years as drench effectiveness can change relatively quickly depending on management strategies within the flock. This will enable you to decide the most effective drenches to use for weaning and the next 2-3 years. Refer the Paraboss website or your sheep health advisor for further details on how best to perform a drench resistance test.

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