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Victoria worms, flies and lice update - December 2015

VIC WormBoss Worm Control Programs

VIC WormBoss Drench Decision Guides


Hamilton: Andrew Whale, Livestock Logic (a.whale@livestocklogic.com.au)

Livestock Logic Recommendations

  • Dry Spring means a good opportunity for only 1 summer drench this year and lower worm pressure next winter
    • Use the most effective combination drenches or new actives
    • Worm egg counts are <150 epg
    • Lambs are monitored regularly every 3–4 wks
    • Mature sheep monitored every 6–8 wks

Conditions remain dry in the south west of Victoria. Luckily, stock prices remain buoyant giving producers confidence in the livestock sector and making purchasing large amounts of fodder a bit easier.

Given we have had a number of dry springs in the previous few years it is a good time to remind producers of the impact this has had on worm populations for the following summer and autumn period. Without moisture (to keep worms alive) and dry standing feed (to provide shade and shelter for worms) we greatly reduce the carryover population of worms for the following year. This makes worm management easier for the following autumn and winter, BUT only if you make use of this. If the environment makes it more challenging for worms, then we also need to reduce the amount of worms living within the host (our sheep).

This means drenching when required.

The following chart shows the impact that a dry versus wet spring has on the following summer and autumn worm population based on our last 3 years of data for South West Victoria at Livestock Logic.

Figure 1. Months of year versus % of sheep that Livestock Logic recommended drenching


This highlights the differences between a wet spring/summer (2013/14) and a failed spring (2012/13 and 2014/15) in terms of pasture contamination levels and exposure of stock to worms. Focussing on the January to April period we see that in a dry spring and summer period, egg counts were very low by January and remained low right through the autumn.

The above led to a huge difference in the amount of worm eggs on pasture at the time of the autumn break and thus stock challenge in winter and spring.

What this means for us in 2016

Provided it stays dry in January–March, with good worm management over summer this year we can reduce the effects of worms for the 2016 winter. The key to this will be monitoring and eliminating the worm population from sheep with egg counts of 150+ epg. While the data above would suggest that second summer drenching requirements will be limited this year, animals must be monitored 6–8 weeks (6 for weaners, 8 for mature sheep) post 1st summer drench in February this year to know that pastures are not getting contaminated in the late summer/autumn period.