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South Australia worms, flies and lice update - July 2020

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides





Adelaide: Colin Trengove, Sheep Health Lecturer (UA Roseworthy campus) (trengovet@icloud.com)

The season has tracked with a more typical winter westerlies pattern where rainfall has been abundant in the southern latitudes and tapers as you travel north. As a consequence, the south-east is having a dream year while parts of the upper north and pastoral zone are in their fourth year of drought. For others in the mid and upper north and Eyre Peninsula, the season is in the balance between a good year and a failed harvest, depending on whether rain arrives in the next 2–4 weeks. The northern and pastoral areas will be hoping for an urgent influx of sub-tropical weather from the north-west or the westerlies to penetrate more northerly…..such is farming.

Recent monitoring reflects rainfall with relatively low counts in the upper half of the state and generally moderate to high counts in the SE. Lambing has limited the submission of egg counts as most producers elect to do mandatory pre-lambing drenching or insertion of capsules. Regardless of strategy, periodic monitoring is advised as pastures are often quite contaminated by mid-winter, enabling worm burdens to steadily rise—especially as a result of the lowered immunity in ewes during lambing. Further monitoring is also warranted to ascertain the need for a drench both at weaning and before summer.

Individual mob counts have been in the thousands in the SE recently, indicative of likely Haemonchus (barber's pole) burdens. Close monitoring combined with cultures or faecal DNA checks is advised to determine which worms are present before deciding on the chemical and strategy to use. Irrespective of whether the dominant worms are Haemonchus or winter scour worms, follow up testing is also advised to check that the drenching has been effective as worms can soon re-emerge if not effectively treated.

The recent contrasting fortunes of producers relative to seasonal conditions have seen many instances of pregnancy toxaemia (twin lamb disease) as well as hypocalcaemia (milk fever). Scanning results have indicated above-average twinning this year and so increased risk for these diseases to occur. It is also coupled with failure to appreciate the needs of ewes bearing twins both from a nutritional perspective as well as the need to minimise stress in the last four weeks before lambing. Current and foreseeable meat prices alone should encourage all sheep producers to strive to maximise ewe and lamb survival as buying in replacements is going to be difficult and expensive. Wool prices are not so rosy and it is anyone’s guess which direction that will take with the ongoing global COVID-19 uncertainty.

As weaning approaches, a worm egg count is useful to assess the worm burden in lambs and potentially the option to assess which worm drenches are effective in your flock. A worm egg count of 250 epg or more is desirable to achieve a reliable DrenchTest result. It is recommended that a drench resistance test be conducted at least every 3 years as drench effectiveness can change relatively quickly depending on management strategies within the flock. This will enable you to decide the most effective drenches to use for weaning and the next 2–3 years. Refer to the WormBoss website or your sheep health advisor for further details on how best to perform a drench resistance test.