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South Australia worms, flies and lice update - February 2017

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides





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

Rainfall in January and February has created both a weed hazard and worm hazard across South Australia. The positive is that no ewe has a nutritional excuse for not getting pregnant (and preferably twins) with the abundance of green feed on offer. The downside is that summer rain tends to result in mostly undesirable weeds dominating paddock feed e.g. potato weed, melons, caltrop and small crumbweed (also called mintweed, goosefoot)—and these can all have undesirable impacts on animal health.

Recent case reports of scours and worm egg counts generally indicate worms are relishing the unseasonal abundance of moisture. While Haemonchus species (barber’s pole worm) have not been prominent, the other round worms of concern (Trichostrongylus and Teladorsagia species) have caused elevated egg counts across all age groups.

A mob worm egg count is still recommended before drenching, as the count may be below the threshold for a summer drench e.g. 100 epg, and a drench may have limited benefit if there is plentiful green feed in the paddock allowing worm larvae to survive and thrive. In addition, most stock are in very good condition for this time of year and so better able to limit the development of worm burdens.

Another problem with summer rain is that it can facilitate an early build up to the worm challenge on pasture going into autumn and winter. This can cause strategic drenching programs to come unstuck. Monitoring several mobs every 1–2 months is critical to assess grazing strategies and drench efficacy to counter the parasite challenge. Best to discuss your drenching strategy with your animal health expert if you are unclear or have any queries about the best option to adopt.

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