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Tasmania worms, flies and lice update - September 2018

Tasmania WormBoss Worm Control Programs

Tasmania WormBoss Drench Decision Guides





Perth: Paul Nilon, Nilon Farm Health (

So, much of Tasmania received about 50 mm for August, and to date September has given us in the region of 15–20 mm over large parts of the sheep producing regions. Again, the notable exception has been the Fingal Valley and the East Coast, which are both still very dry. The equinoctial gales are starting to bite. They make the weather unpleasant (try casting a fly in 70 km/hr winds) and reduce the effective rainfall. Some paddocks prepared for spring sowing are blowing like the American tourists in the film, In Bruges.  Check out this classic.

Travelling around the countryside, lambing ewes are generally in good condition with adequate, if not brilliant, tucker in front of them. Consequently, lamb marking drenches should not generally be needed. Yesterday, at Fingal, I saw ewes and lambs on 600 kg semi-green (typical of a bowing green). Not surprisingly, the ewes were light and the lambs hungry. Both were scouring, so I suspect (roadside diagnosis) that both will need drenching at lamb marking. The warning signs are:

  • Inadequate pasture.
  • Light ewes and starved lambs forcing early grazing
  • Scouring in one or both.

In my experience it’s a waste to drench ewes and not the lambs. Do both. Mobs that have to treat at marking (as opposed to electing to treat) should consider early weaning: as early as 9–10 weeks after the start of lambing.

Return of the Merino: There is a bit of a stampede to increase Merino numbers. This raises the question as to whether they are inherently more susceptible to worms. The answer is yes, maybe, probably. As most Merino genetics are derived from a semiarid background, it’s not surprising that they do not like worms, and efforts to select for robustness are relatively recent. There are also some papers to support the notion.

However, a lot of the worms we see in Merino flocks in the high rainfall areas result from the way we run them: high stocking rates with marginal nutrition, and the fact that a large proportion of the lamb drop is kept. Light Merino weaners are worm factories.

Poor nutrition from high stocking rates should be reviewed in the light of the LifeTime Ewe Management (LTEM) work, and the value of livestock.  If that does not convince you, give thought to increasing animal welfare surveillance.

When all is said and done, to run Merinos in many parts of Tasmania you have to control the winter parasitism in the young sheep. If you fail, not only will you lose many hoggets, but the paddocks become inexorably contaminated for lambing ewes. Please consider some integrated parasite management (IPM): particularly Smart Grazing.


Cattle Treatments: While the cattle specialists will not twig to this as Cattle ParaBoss is not up and running till next year, those with mixed sheep and beef enterprises may find it useful. In the last few weeks I’ve fielded a few questions about spring worm treatments. Herewith:

  • If cattle are in good condition (>2.5 or 2.75 for heifers) and have reasonable prospects there is little point in giving a mectin treatment for lice. The lice population will crash in the next few weeks as spring progresses. They look ugly, but so do I and I do not routinely treat myself for lice or ugliness.
  • Young cattle (1st and second calvers) that are light (<CS 2.75), particularly with poor spring prospects, will benefit from a worm drench.
  • Rising 1 yo cattle need a spring drench. The ideal timing is 10 o’clock after a cup of tea. In other words, now.
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