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Victoria worms, flies and lice update - May 2019

VIC WormBoss Worm Control Programs

VIC WormBoss Drench Decision Guides





Hamilton: Lexie Leonard, Livestock Logic (

Recommendations from Livestock Logic.

  • Worm egg count (WEC) monitoring before the pre-lamb treatment is vital to be able to adequately assess worm-risk of individual mobs.
  • Weaners/hoggets should have WEC tests every 4–5 weeks over the winter period.
  • WEC results from mid-June onwards will be a good indicator of the effectiveness of your summer and autumn worm control program.

There has been some welcome rain in the Hamilton region last week, with the majority of areas receiving 25–30 mm over a few days. While this does signify the autumn break, some follow-up rain is needed to ensure adequate pasture growth coming into winter. The arrival of the rain also signals the start of the winter worm period, with enough moisture falling in most areas to soften faecal pellets and allow larval release from eggs onto pasture. Total rainfall recorded for Hamilton as of 15th May was 35 mm for 2019, compared with 62.8 mm in May 2018. 

Given it has been quite a dry previous 5 months, there has been very little pasture growth up until this period. With the break coming slightly later this year, there will be less time to grow pasture before winter starts, and we anticipate a higher worm challenge over winter compared to last year. This will be especially important for any June or July lambing mobs. It is anticipated that WECs will rise sharply from mid-June, which will coincide with the start of lambing for many flocks. However, properties and flocks that had good worm control over summer and autumn should have a low risk of worm challenge this winter as it has been relatively dry. 

It is vital to assess mobs and lambing paddocks for risk when deciding on whether to pre-lamb drench, and whether a short or long-acting drench is more appropriate for individual mobs. Worm control over summer and autumn and WEC monitoring results will have a big impact on risk factors for individual lambing paddocks. We have also found many mobs are in lighter condition this year compared to previous years and this will also increase worm risk over winter lambing.

Mob risk factors include age, twins, condition score, mob size and length of lambing. Combining this with pasture risk (Food On Offer and potential larval challenge) will give a good indication of projected worm risk over June–July period. 

If your WEC results begin to creep upwards from June onwards, then it would be an excellent time to assess and re-structure your summer worm control program for 2020. 

For May 2019 state outlooks, please follow the links below:
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