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New South Wales worms, flies and lice update - June 2021

NSW WormBoss Worm Control Programs

NSW WormBoss Drench Decision Guides






Central West LLS

Coonabarabran: Kate Atkinson, DV (

Lambing is approaching in the district for many landholders. The increased nutritional demands in late pregnancy and early lactation suppresses immunity in sheep and this can allow worm burdens and the susceptibility of ewes to increase at this time.  The ramifications of high worms during pregnancy can be severe with both production loss in the ewes but also contaminated paddocks infecting the lambs when they start grazing. Performing a worm test will indicate the burden in pregnant ewes and allow for an informed decision around prelambing drenching. 

When a prelambing drench is indicated, the ideal management includes drenching with an effective drench (usually a multiactive drench or one containing a newer active such as monepantel or derquantel) and then moving the ewes to a ‘clean’ paddock for lambing. Aim to return ewes to pasture/feed as soon as possible when heavily pregnant to avoid other health issues occurring (i.e. hypocalcaemia, pregnancy toxaemia).

Coonamble: Jillian Kelly, DV (

A question asked this week: "can you give me a sheep worming plan for the year for the Coonamble district?" The answer to this was "no, sorry!" This is because our rainfall is variable, not seasonal. This means that our worms (like the rain) don't come at any set time of year, and we can't have a fixed drenching plan that fails to consider variations in moisture and temperature.

If you drenched at fixed times of the year without wormtesting first, especially if you use the same chemical classes repeatedly, you're likely to end up with wormy sheep and drench resistance. The best way to manage worms in this district is to wormtest frequently and only drench when necessary, using multi-active drenches. 

Many producers who have been doing this have only drenched sheep very occasionally (i.e. once or twice) over the past three to four years! The hot, dry conditions the drought brought were an excellent way of cleaning up the larvae in the environment, and a well-timed effective drench leads to long-lasting benefits and low worm counts.

In other news, cattle are visibly starting to rub from lice burdens and some producers are choosing to apply backliners. Remember, cattle rarely have an economic impact due to lice burdens, so treatment is likely to not be warranted. It is also worth noting that most lice treatments target internal parasites as well, so consider how repeated yearly use of the same active ingredient may be impacting worm resistance in your cattle.  

Dubbo: Sarah Maher, DV (

A wet start to winter has resulted in a reduction in new Barber’s Pole burdens and an increase in the percentage of scour worms causing burdens. Producers are encouraged to do a WEC and larval culture three weeks after the change in season, that being the first frost or cold snap, first spring rain, etc. This will allow them to target worms appropriately. A larval culture may tell you if your previous drenches have been effective or if you are still dealing with the Barber’s Pole carry-over from a mild summer and warm spring. Producers should begin planning what drench they will use at weaning for their autumn drop lambs and plan for clean pasture to move the lambs on to. Producers are reminded that a clean pasture results from a 95% reduction in larvae which is most commonly achieved by spelling paddocks, the amount of time a paddock needs spelling to reach a 95% reduction is dependent on environmental conditions. A graph which can be used to estimate the level of larval reduction on a pasture can be found here.

Forbes: Belinda Paul, DV (

The Forbes area has had a good start to the winter growing season with good rainfall and a favourable weather outlook. Therefore, conditions in the paddock will be favourable for worm larval survival particularly scour worms. Many autumn lambers will be thinking about weaning. As lambs are very susceptible to the effect of a worm burden at weaning, they should be drenched with an effective drench containing at least three active constituents or a combination product with one of the newer generation actives and should be put on a low-risk paddock. Performing a worm test two weeks after drenching will provide the producer with valuable information with regards to the effectiveness of the drench used.

Nyngan: Kelly Wood (

With the cool, wet weather here and lambing just around the corner for many producers, now is the time to get your winter worm plan in place. The large number of twins scanned around the district, the delayed appearance of winter medics and fodder crops, and the late shearing that many producers have been forced into means that extra attention needs to be paid to your lambing ewes and young stock over the coming months.

Increased metabolic stress from a heavy worm burden is likely to exacerbate the energy challenges placed on sheep during cold, wet weather and late pregnancy. On top of this, many producers will be contending with higher-than-normal pasture larval levels due to the mild summer. Regular worm-testing and reactive drenching based on WEC thresholds will be critical in minimising losses and maximising profit this season.

Producers are also urged to use a strategic pre-lambing drench and well-prepared lambing paddocks wherever possible. If you are concerned that your lambing paddocks may not have been spelled sufficiently or properly prepared to reduce larval burdens, it may be useful to conduct a worm test on the ewes immediately after lambing to assess the need for a drench at marking.

Use the WormBoss Drench Decision Guides published on the WormBoss website to optimise your drenching strategy and reach out your local LLS livestock officer for advice tailored to your enterprise.

Riverina LLS

Gundagai: Elizabeth Ferguson (

The cold weather in the Riverina has finally seen the end of our fly season, with some producers reporting struck sheep as late as May.  FlyBoss has some excellent tools to plan ahead for shearing, crutching and chemical treatments to minimise the prevalence of fly strike – well worth a look!

With lambing well underway in the Riverina, the number of pre-lambing worm tests being conducted has dropped off.  For those that have been submitted, there has been a general shift in worm mix away from Barber’s Pole to scour worms – not unexpected given the colder weather we’re experiencing.  However, it is still prudent to ensure that any worm test is followed up with larval culture and differentiation, because this will give a clearer picture of what is happening in the paddocks with the sheep and how to interpret the worm test.

It is also a good idea to begin to think ahead to next season and start preparing paddocks.  Safe paddocks are essential for lambing and weaning, and, if spelling the paddock to reduce larval contamination, this needs to be conducted in the warmer months, so it’s a good idea to plan ahead to determine what paddocks are going to be used for which purpose.

Murray LLS

Deniliquin: Katelyn Braine DV ( and Linda Searle, DV (

With lambing underway in the west of the Murray region and weaning coming up, now is the time to make sure you have a low worm risk or “clean” paddock to place your lambs on at weaning.

Weaners are more susceptible to worm burdens because they have an immature immune response and suffer stress during the separation from the ewes. Lambs which are weaned on a low worm-risk paddock will face a lower worm challenge, allowing for higher growth rates and will decrease worm contamination of the pasture.

Conducting a WEC on your lambs prior to weaning is also a helpful way to determine if drenching at weaning is required. Drenching of weaner lambs is warranted when the WEC threshold is greater than 300 eggs per gram (EPG) in the pastoral areas and greater than 150 EPG in the non-seasonal areas of the Murray region.

While the cold and frosty conditions over winter can prevent the ability of worm eggs to hatch (depending on the worm species and daytime maximum temperatures), it is important to understand that this is not the same for worm larvae. The larvae that develop in Autumn can survive throughout winter due to protection from the soil and pasture and still pose a risk of continuing to infect livestock grazing those pastures. Regular WEC can be conducted during winter if you suspect issues with worms to determine if drenching is needed.

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