Back to State Outlooks

Tasmania worms, flies and lice update - July 2019

Tasmania WormBoss Worm Control Programs

Tasmania WormBoss Drench Decision Guides





Perth: Paul Nilon, Nilon Farm Health (

You know it’s wet when water lies in gateways like a homeless pup, and every step produces a squelch as you walk across the paddocks. Except it’s not that wet. Here at Perth (Tas, for the interstate readers), we are below an average year to date because of a dry January and April. Other areas are well behind the line, and the east coast is a rare class of awful. Some snow made for an excitng trip to a job recently, see image below.

Water lying around is as much due to our poorly drained clay soils and some recent falls. Whatever the cause, it is an alarm bell for a good season for black scour worm, as warned in May and June state outlooks. So, beware.

There have been many worm egg count tests conducted from mid- to late-pregnant ewes, but little else. As in the last report, the counts in Merino ewes, particularly those on the light side, are on the rise. So, act accordingly (see last May and June reports), particularly if your place is wet and the ewes are light. Merino weaners are similarly vulnerable.

As the report is a bit light this month, some case studies may be helpful. Two clients rang last week with pre-lambing drench questions. Here is a precis of the information and the decision:

Farm 1. A prime lamb enterprise in the north of the state (800 mm rainfall). The property is wet (but not as bad as many years). Ewes in body condition score (BCS) 3+ (I saw them in late June) and they will lamb down on 1500–2000 kg green dry matter (GDM). Egg counts on all mobs of ewes showed the highest count of 45 eggs per gram (epg). Should he drench in time for a 10th August lambing?

In any public forum, I would usually recommend a pre-lambing drench. This is an exception. The ewes are in good condition and lambing paddocks adequate (indeed, very good). An additional consideration is the possibility of barber’s pole on the irrigated paddocks: in this case, the circles are not used for lambing. So, the decision (always the farmers) was taken not to drench, and continue monitoring.

Farm 2: This is a mixed cross-bred (XB) and Merino property in the midlands. Rainfall is well below average, and while the XB ewes are in good condition, the Merinos are lightish. Moreover, the Merino portion will be lambing in semi-improved country (lots of shelter, but a long march between blades of grass).

The owner was concerned that after 10 years using a moxidectin (mox) long-acting (LA) drench he should change before resistance became an issue (praise the Lord)!

In this case, there was no worm egg count data and no resistance information. Experience suggests that some of the semi-improved country can be a worm trap, particularly if it has been grazed by light ewes or weaners in the autumn and early winter. Three recommendations were made and accepted by the farmer:

  1. Treat Merino ewes with mox LA as previously. They will be doing it hard. A primer is also a good idea (despite LA’s extraordinary robustness).
  2. XB ewes should be more robust, so give them a short-acting drench (preferably one of the new compounds (monepantel or derquantel ).
  3. Sit down before weaning to plan worm control for the next few years. This property lends itself to smart grazing so I will be pushing that at the planning session.
For July 2019 state outlooks, please follow the links below:
Back to State Outlooks