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Western Australia worms, flies and lice update - February 2016

WA WormBoss Worm Control Programs

WA WormBoss Drench Decision Guides

Albany: Brown Besier, DAFWA (

After the unseasonal rains, producers should continue to check sheep using worm egg counts. If counts are not very low then a re-drench may be needed. The current recommended action is the same as last month’s and is included again.

Action now recommended

Firstly, assess whether there has been any change to the worm risk. In many situations there will be no change to the usual advice: drench ewes in early-mid autumn, and check worm egg counts of summer-drenched sheep towards the end of summer.

However, where a general germination occurs, there are some revised recommendations:

Sheep given summer drenches: Resistance now affects all but the newest drench types, and if, for instance, abamectin, moxidectin or even a triple combination type have been used, you can only be sure they were fully effective if you’ve tested for drench resistance.

Action: if not sure the drench worked fully, take dung samples for worm egg counts on some representative mobs. If the average count is more than about 100 eggs per gram, a re-drench within a week or two is recommended. If it’s lower, but still over about 50 eggs per gram, re-check in 4–6 weeks, and again, re-drench if over 100 eggs per gram.

Ewes not drenched in summer: In most years, autumn drenches should be given in late March or early April, before conditions change to allow general worm egg development on the pasture. If this occurs earlier due to the rain, this drench should be brought forward, and given by about mid-February. (You can take worm egg counts to check the need, but in the great majority of ewe mobs that have not been drenched since winter or spring, a drench will be warranted.)

Barber’s pole worm areas: Green pasture in summer favours barbers pole worm development, and we’ll certainly see more of this than in most years. Worm burdens will take 5–6 weeks after the rains to develop, and it’s difficult to predict whether they will be significant in any particular mob. The best guide is whether green pasture has persisted, as is especially likely on perennial pastures. Worm egg counts on a couple of representative mobs at that time will indicate whether a drench is needed, and whether a product with a long-acting effect against barber’s pole is justified.

In summary, where rains have been unseasonably heavy there is a higher risk of worm problems, whether now or later in the year. Timely action now will determine whether 2016 unfolds as a severe worm year on your farm, or whether worms can be managed by normal tactics.


Esperance: Nicole Swan, Swan’s Veterinary Services (

In mid-January, the district had a significant rainfall event. This was fantastic for the perennial pastures. A lot of the district is green including many stubble paddocks. Will it stay green?

Following this rain we have done a number of WormTests (WEC) especially of weaners.

Weaners that received an effective (in these cases Startect®) drench onto stubbles at the beginning of summer, have had low counts 3 weeks after the rain. Counts averaged 10 epg.

Weaners that were not drenched onto stubbles had an average count of 105 epg and will require drenching soon.

Other WECs conducted recently were from red tag sheep. These had not been drenched since August. All of these mobs required drenching. No further testing was conducted, however, high counts in the absence of scouring were indicative of barber’s pole.

Drench advice between now and April 1st will depend on WECs, the class of sheep, previous drenching history of each mob, and the weather.

Weaner mobs with average counts greater than 100 epg should be drenched with an effective drench prior to April 1st.

Ewes that did not receive a first summer drench should be drenched early April.

However, if we get an early break e.g. March, then drench 2 weeks after it is green.

From April 1st larvae survive in the pellet due to moisture available from this time onwards, so sheep should be drenched at this time. DO NOT wait for the break.

For February 2016 state outlooks, please follow the links below:
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