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South Australia worms, flies and lice update - April 2016

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides

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

Graziers and croppers alike are patiently awaiting the fabled break in the season on Anzac Day. Parts of the Eyre & Yorke peninsulas, mid north, Adelaide Hills & upper SE have received notable thunderstorms in recent weeks, but most graziers are reliant on feeding grain and hay, especially to late pregnant and lactating ewes.

Recent egg counts around the state indicate most stock, irrespective of age or pregnancy status, have significant worm burdens. However, as is often the case, there is as much variation between mobs on individual properties as there is between properties and regions.

Drenching in autumn is likely to have little impact on winter pasture contamination as larvae hatched from worm eggs now on pasture will survive for many weeks due to moderate temperatures. However, a drench now can be vital to weaners and pregnant ewes as their immunity may be limited or waning.

The choice of chemical for an autumn drench must be different to that used during late spring/summer or else drench resistance will be encouraged. This similarly applies to the convenience of using a drench combined with a vaccine (e.g. Eweguard) in the lead up to lambing. If this is routine practice, care needs to be taken to avoid using moxidectin in the months preceding this planned drench.

A pre-lambing drench is usually discouraged, but if ewes are below the ideal condition of score 3, feed is limiting and egg count is approaching 100 eggs per gram or more, then an effective drench prior to lambing is critical to minimize worm impact prior to weaning.

The important points are that the livestock manager needs to be well prepared for lambing, which includes monitoring worm egg count, ewe condition score and feed on offer. With these simple strategies in place, parasite management should be well managed. Contact your animal health advisor if you have any queries regarding these strategies. 

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