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Tasmania worms, flies and lice update - September 2014

Perth: Paul Nilon, Nilon Farm Health (

In the last month there has been substantial rain over much of the State:  nothing like last spring but enough to keep the grass growing and set the stage for a reasonable spring.

After months of fairly high worm egg counts, things are settling down a bit. All but the very late lambers have lambs everywhere. On what I’m seeing very few will need to drench at lamb marking as the ewes are milking well and given the widespread use of long-acting products many mobs will just about be worm-free. It’s instructive to monitor long-acting products throughout their payout period. 

The next big decision will be drench choice for weaning/first summer drench for most producers.  While there is endless debate about the value of drench rotation, research from WA shows that those that do rotate their drenches generally have a better resistance status.  I’m particularly keen that people maintain some semblance of mectin workability so that we can fall back   to mectin based long-acting products if needed.  Therefore, give some thought to changing to a new active, at least for the first strategic drench.

For strategic drenches to work (that is, to help pasture decontamination) you need be as close to 100% effective as possible. The strategic drenches are particularly important on merino places running sheep on perennial pastures.

We have two drenches that should work 100%:  Zolvix (Monepantel) and Startect (derquantal and abamectin).  Zolvix has been used widely, but sparingly, in Tasmania.  Startect is a new novel combination and is expected to be released in Australia in late September. The way to preserve both these drenches is not to use them, but this will do little to improve the overall resistance status, nor will it encourage pharmaceutical companies to invest in the sheep industry.  By using both drenches with some regularity you may avoid the possibility of having them as the only alternatives.   If using them in prime lambs make sure your marketing plans accommodate the ESI.

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