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Victoria worms, flies and lice update - July 2018

VIC WormBoss Worm Control Programs

VIC WormBoss Drench Decision Guides





Hamilton: Andrew Whale, Livestock Logic (

Livestock Logic Recommendations:

  • August is our danger month for sheep mortalities from worms—weaners and wethers are highest risk
  • Egg counts are now highly reliable for ewes pre-lambing to assess their requirements for drenching over the lambing period

We continue to have a great season in the South West of Victoria with some recent rain in late July starting to get things almost too wet. We have full soil moisture profiles and are now getting some runoff. The next month should see pasture growth rates improve as the days lengthen and temperatures start to warm up.

Egg counts are steadily rising, which is typical of winter conditions. Egg counts are tracking in a similar manner to that of last year and to date it has been a moderate worm pressure year. As always, August is the month where we typically see sheep health deteriorate. This is a result of reduced nutrition in the weeks leading up to August, and the increased level of worm burden on pasture. These factors typically impact weaners that have a lower immunity to worms and adult wethers that are concentrated onto less feed to make room for pregnant or lactating ewes. While all sheep need monitoring, these two classes of sheep are typically the ones to WormTest over winter.

Those that administered long acting capsules or drenches to ewes pre-lambing, or weaners for the winter, should consider testing the efficacy of these products. Long acting moxidectin should give us a zero egg count day 50 after administration if working at 100% efficacy, and Dynamax/Bionic capsules at day 80. Those two dates are the ideal times to test the efficacy of these products. It is important to know that they are working well if they are a part of your worm management plan. If they are starting to break down you need to be aware of this and consider alternative options to manage worms.

The chart below shows the current worm challenge compared to that over the previous 2 years.

This graph shows that the challenge to date is not as bad as last year, but regardless, there is strong evidence that the worm challenge only increases from here as larval worm levels increase on pasture.


Continue to monitor weaners and lambs every 2–3 weeks, and mature sheep every 4–5 weeks throughout the winter and early spring. The graph also shows that while there is variation annually in worm challenge, there is also a big spike in drenching requirements in the late winter and spring period

For July 2018 state outlooks, please follow the links below:
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