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Queensland worms, flies and lice update - April 2021

QLD WormBoss Worm Control Programs

QLD WormBoss Drench Decision Guides





Brisbane: Maxine Murphy, Veterinary Parasitologist (

It took a while, but the rain did come. 

Daytime temperatures are still reaching over 30°C in many regions. Still, until temperatures drop below 18°C, barber’s pole will stay a threat — especially if the soil moisture profile is good and the grass is green and actively growing. 

Currently, the cooler night temperatures are only slowing the speed of the egg hatch, not stopping it. 

As a general rule of thumb, temperatures in almost all of Queensland remain warm enough throughout the year to support the barber’s pole cycle, albeit at a slower pace during the winter months. A moisture deficiency is more likely to stop worm development than lower temperatures.

April is an excellent time to do WormTests; select a mob representative of about three other mobs of the same class to test and repeat four weeks later. 

A single worm test result is just a snapshot in time and not the whole picture; it cannot indicate if worms are building, falling or remaining stable. Only a follow-up worm test four weeks after the first can warn if a drench is needed. For many mobs, this drench, preferably a short-acting combination drench, may well coincide with the pre-lamb drench.

April is the time to start locking up paddocks ear-marked for spring lambing. Removing sheep for a few months will stop further egg drop onto paddocks. Spelling gives paddocks time to recover from grazing and for infective larvae to die. Grazing with adult cattle will assist in removing remnant larvae. Paddock preparation will take about four to five months on the tablelands, whereas on the drier slopes and plains allow approximately three to four months. 

Or you could take advantage of the delay in egg release onto pasture that drench treatments can give. After a short-acting drench, this time is 21 days. For drenches with any length of protective period, it’s the protective period plus 21 days. Caveat: drenches will probably not be 100% effective in all sheep, so take care of this strategy as sheep may still carry worms and contaminate pastures. 

Some definitions relevant to preparation for spring lambing:

The condition of a pasture can be defined by the amount of green herbage mass in kilograms dry matter per hectare (kg DM/ha) 

  • Poor: less than 600 kg DM of green herbage mass/ha 
  • Moderate: 600–1200 kg DM of green herbage mass/ha 
  • Good: more than 1200 kg DM of green herbage mass/ha

Body condition scores can define the condition of sheep 

  • No breeding ewe should be in score less than 2.
  • Ewes in score 2.5–3.5 will provide optimum production and profitability.
  • Ewes that are too thin (<2.5) will have poor production, increased risk of mortality and poor reproduction.
  • Ewes that are too fat (>3.5) will have good production but stocking rate will be compromised which has a direct impact on profitability.
  • No growing sheep (i.e. weaners) should be less than score 2

When planning a drench, also plan to do a DrenchCheck. This test is essentially two WormTests on the same mob taken 10–14 days apart to get an idea of drench efficacy. The pre-lambing drench needs to be very effective against the worm burden.

For April 2021 state outlooks, please follow the links below:
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