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South Australia worms, flies and lice update - September 2020

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides





Adelaide: Colin Trengove, Sheep Health Lecturer (UA Roseworthy campus) (

An unusual low pressure from the north has brought up to 100 mm of fortune-changing rain to the pastoral zone and upper north. It has saved crops and no doubt created a potential spring worm and flystrike explosion. However, this will be moderated by the low stock numbers and worm burdens in the pastoral areas after a series of tough seasons.

The good season continues in the lower Eyre peninsula, KI, Fleurieu and South East with monitoring indicating two thirds of mobs needing a drench. This reflects the extended opportunity for paddock contamination following the early break combined with a steady rise in worm burdens since lambing.

Most producers across the state have experienced exceptional lamb marking percentages following the good start and relatively dry winter, affording excellent lambing conditions. Significant worm burdens in ewes sets up an ideal opportunity for drench resistance testing (DrenchCheck) at weaning. Lamb worm burdens would be expected to be sufficiently high by weaning to enable a comparison between which drench groups are effective. Consult your animal health advisor if you need assistance to arrange a drench trial.

Care is needed to ensure lambs have access to low worm-risk pasture at weaning to promote optimal growth. This generally means moving them onto pasture with both good quantity and quality, as well as having been ungrazed by sheep for several months. Hay aftermath is ideal or pasture grazed by cattle only during winter or potentially drenched adult dry sheep.

Monitoring for worms should continue in the lead up to summer to assess the need for a summer drench. Similarly, monitoring for flystrike and lice is always important to also minimise the risk of production loss from these parasites.

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