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Tasmania worms, flies and lice update - August 2016

Perth: Paul Nilon, Nilon Farm Health (pandonilon@bigpond.com)

It’s been a relatively dry month with only about 35 mm recorded at our local station to date. However, after the 3 preceding months, even this trifling amount is enough to keep paddocks oozing water and bog vehicles that stray off the tracks.

Last month I warned of the perils of very wet winters: when there is water lying around there is a high risk of black scour worms. In the run up to lambing, worm egg counts (WECs) for most clients remained low. Consequently, most chose to go with a short acting pre-lambing drench, and a few brave souls chose not to drench. In contrast, Bruce Jackson from DPIPWE reported several cases of very high parasitism. I suspect (but do not know) that these would be in lighter merino flocks where the opportunity to plan lambing paddocks was severely limited.

By now, the pre-lambing drench strategy will be in place. Time to consider what to do if you choose not to drench (or used a short-acting drench) and it goes pear-shaped. Drenching at lamb marking is the obvious answer. If you have to drench the ewes, you should also drench the lambs. A parasitised ewe will milk poorly, and force the lamb to graze. If this occurs the lambs will also become parasitised. If you think lambs don’t acquire worms early in life, spend 20 minutes or so watching how even well fed lambs spend a deal of time with their heads down from just a few days old.

Most producers should not need a lamb-marking drench. If ewes are light (CS <2.5), pasture short (less than 1000 kg GDM), or if the ewes and lambs are daggy you need consider a drench. If you miss (or have missed this chance) consider an early weaning.

Now is the time to plan weaning paddocks. In my experience mixed perennial pastures are best, followed by straight grasses. New Brassica crops and straight legumes may be a bit potent for the newly weaned. While nutritional adequacy is paramount (at least 1000 kg of green material), there is still time to make weaning paddocks less contaminated. Larval availability drops off rapidly in the spring and you can use this decline to your advantage. Three months without grazing is not tenable, but the alternatives include:

  • Grazing with cattle (particularly useful for irrigated circles of grass: finish your 1-year old calves before stocking the circle with lambs).
  • Hay making. I’m not advocating you make hay, but if you must, the cut paddocks are (relatively) clean because of the spell time before cutting. Do not overestimate this: if the spell time is short they be contaminated. Moreover, Nematodirus seems to resist hay-making as a means to decontamination.
  • It’s best to avoid weaning onto the lambing paddocks. However, if the ewes have been capsuled or given an LA injection, the lambing paddocks may be relatively clean. Moreover, whether we like it or not, the lambing paddocks are frequently the best pasture paddocks so you may have no option.

Finally, don’t just plan the first move: map the process well into autumn. After Christmas make use of grass seed crops, grain stubbles (but don’t overestimate their nutritive value) and new Brassicas becoming available.