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Tasmania worms, flies and lice update - October 2020

Tasmania WormBoss Worm Control Programs

Tasmania WormBoss Drench Decision Guides





Perth: Paul Nilon, Nilon Farm Health (

For the weather you can attend this site. I suspect I may have previously referenced the weather according to Rosetta Tharpe, but we will all need to shake our tail feathers to dry them.

Very little is happening with worms. Weaning has not started, so the only reports are from merino hoggets, some of which are getting higher worm egg counts. Previous reports have suggested letting the counts blow out a bit to promote immunity. An alternative is to drench the tail of the mob only. This is where a large proportion of the worms are, and the sheep with the really high counts also skew the average upwards. The tail of the mob are those noticeably lighter and those with dag. Now, this is not an “every-day” suggestion, so contact me to discuss if you wish to try this “targeted treatment” approach.

More on Tail Length: Let it not be said I get a bee in my Akubra, but here is a link to a hiking video (in Colorado) that has a mob of sheep in the first minute. Remark the tail length! This in a country that has neither Lucilia cuprina nor any notion of how to control population disease, but they seem to have their tail length right. Surely we can do it? For the walkers amongst you (and I know many of my clients are), the rest of the video is not worth the effort.

Flies will be active early. I know this because the lawn mower is bogging and the sweat flowing. Warmth and moisture, nothing else is needed. For those given to the risk approach to fly control this is the high-risk scenario. Consider the following:

  • Mulesed lambs must be treated with a fly preventive (dicyclanil is drug of choice). It can be applied with Trisolfen™.
  • All weaned lambs should be treated unless shearing is scheduled within weeks of weaning.
  • Consider giving whole-flock treatments early. This acts like a strategic drench and reduces the build-up of the fly population. Work done by the Mackinnon Project some years ago suggested October was the ideal time for an early strike (pun intended): I suggest that Tasmania is a bit behind so any time till mid-November may be OK.
  • Treatments for finishing lambs are always a juggle of ESI and WHI against prolonged protection. There may not be a single-treatment option. You may have to:
    • Split early and late finishers and use a shorter acting (and shorter ESI) for the earlies.
    • Repeat treatments depending on how the season progresses and when the lambs are shorn. It is not a good idea to repeat a treatment from within the same chemical group in the one season. So, if you use dicyclanil or cyromazine first up you should look at a mectin, spinosad or imidaproclid for the second treatment.
  • Big rain events shorten protective periods, even for dicyclanil that normally sticks like a militant hound. If treated sheep receive a biblical rain watch for flies.
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