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Queensland worms, flies and lice update - March 2021

QLD WormBoss Worm Control Programs

QLD WormBoss Drench Decision Guides





Brisbane: Maxine Murphy, Veterinary Parasitologist (

Scattered showers and rain have fallen over parts of the Maranoa and western Darling Downs this month and will have kept the barber’s pole menace ticking over. Substantial rain is predicted for the last half of March — let's hope it eventuates over your patch.

Soil moisture profiles are building, which is encouraging.

Temperatures are still ideal for barber’s pole infections and remain so for most of the year — except for areas around Stanthorpe that experience very cold winters.

After the rain, it’s back to basics: 

  1. WormTest now, and in four weeks.

There will be larvae on the ground from previous rainfalls, and their numbers will build dependent on the level of rain received this month and the intensity of stock, which may be crowding around green pick or marooned on higher ground. Additional larvae are derived from eggs shed from wormy sheep that weren’t drenched in the previous few months.

If there is evidence of a worm population building, check the weather outlook; if it looks like more rain, then a highly effective combination drench is needed to kill adults and stop further egg contamination of pastures. 

“If you have fat sheep on good pastures, you don’t need to drench until 1200 eggs per gram (epg).” This is not always the Queensland situation. Subtropical pastures are never as lush as temperate pastures, and laboratories usually recommend drenching earlier than 1200 epg, particularly in young stock if the outlook is for continuing good moisture conditions. The unknown in this situation is the number of larvae and immature adult worms in sheep. They can’t be detected until they mature into egg-laying adults often 2–3 weeks later.

As the weather dries out feed quality will fall off, and sheep carrying reasonable numbers of worms may succumb to chronic anaemia if not drenched.

If conditions rapidly return to dry and very warm most larvae on the ground will perish before being taken up by stock. A WormTest will be your best guide. Also, check point #3 in the link for additional ways to assess stock for worm burdens.

  1. WormTest fourteen days after drenching.

A 90% reduction of a 5000 epg worm burden leaves a count of 500 epg, which could build within four weeks given wet conditions. Keep checking drench efficacy because a drench that worked well today may not work so well next season!

Do NOT drench just in case, and don't use a single active drench that might not give a 98% kill. These two measures will help to keep drenches effective.

The last thing you need is to have a good finish to autumn and think all is well, and then fall into a heap in early winter because you didn’t do enough WormTests.

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