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South Australia worms, flies and lice update - October 2016

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides


Adelaide: Colin Trengove, Sheep Health Lecturer (UA Roseworthy campus) (trengovet@icloud.com)

The unusually long spring continues resulting in abundant pasture growth, delayed harvest and difficult conditions for those making hay. Rainfall in October has been about average on Eyre Peninsula through to mid-north and up to double the average for Adelaide Hills through to the south east. The abundant feed has a double benefit of promoting good condition and health in livestock plus diluting access to worm larvae. Perhaps the downside is that trace element deficiencies are most evident in wet years resulting in lowered immunity and so increased susceptibility to worms and other potential diseases.

Recent worm counts have not indicated a distinct pattern probably reflective of variable drenching and pasture management practices. Some weaners have had high counts over 600 eggs per gram (epg) in a WormTest indicating either failure to drench at weaning or significant pick up since weaning. Other counts have been low to zero indicating good weaner management. The abundance of feed at this time of year should ensure optimum growth rates and effective worm control provided worm burdens are low going into spring. However, the fact that some sheep still have high counts highlights that monitoring needs to continue throughout the year and especially in the most susceptible class of stock—weaners and hoggets.

Monitoring prior to summer is critical to ensure all classes of sheep are not carrying excessive worm burdens when feed quality and quantity diminishes. Being opportunists, worms will impact health and production whenever nutrition is limiting. In order to minimise the risk of drench resistance it is preferable not to drench during summer. However, high egg counts demand action and a strategic drench in summer can effectively minimise or eliminate worm concerns the following winter.