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Victoria worms, flies and lice update - October 2019

Hamilton: Andrew Whale, Livestock Logic (a.whale@livestocklogic.com.au) and Lexie Leonard, Livestock Logic (l.leonard@livestocklogic.com.au)

Livestock Logic key recommendations:

  • Informed decisions on drenching cannot be made without worm egg count monitoring.
  • Start planning your summer drenching strategy now.
  • Condition score ewes to help inform drenching and pasture management decisions.
  • Monitor weaners closely and ensure they get the best pastures coming into summer.

It is hard to believe that we are already fast approaching summer. In the Hamilton region, a run of fresh mornings, cool days and moisture has kept a feeling of spring in the air. Pastures are generally looking very good with good growth and quality. Rain forecast for late October is helping keep hopes up for a further 6 weeks of good spring growth.

With this in mind, we are expecting summer drenching programs to follow a similar pattern to last year, where blanket drenching at any stage was not appropriate. Many mobs did not have worm egg counts (WEC) high enough to warrant drenching, and in many areas, pastures did not dry off until Christmas. WEC monitoring for summer drenching decisions should start to happen around the end of November when pastures begin to dry and faeces become firm. However, we expect that not many mobs will be ready for drenching until mid-late December. The chart below compares drenching requirements of this spring to those of last year’s spring: the lower WECs this spring cements the need to monitor, and not blanket drench sheep according to the calendar.

Worm egg count monitoring will help decide the optimum time of summer drenching, if required. Drenching too early will increase the need for a second (or third) drench over summer as there will be larval pick-up post-drenching. Drenching too late will allow significant numbers of worm eggs and larvae to survive in the faeces over summer to become the worm problems next year.

Summer drenching should be combined with pasture management and stock rotations to maximise benefits of drenching.


If you have not conducted a drench resistance trial on your property in the last 3 years, now is a good time to start considering if you have any suitable mobs. Weaner mobs with bulk WEC of >300epg are ideal mobs for conducting drench resistance trials.

To date, we have not seen a large amount of fly activity as temperatures have remained cooler. We expect fly activity to increase as temperatures start to rise over 18°C during the day, especially if there are continued rain events. Ensure your flocks have a fly control program in place and based on either chemical or mechanical prevention.