Tasmania worms, flies and lice update - June 2019

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

The weather has been typical June fare: frosty mornings, plus or minus a fog that curls the tomatoes and closes the airport, interspersed with south-westerly fronts. The latter has brought good rain to many areas of the north. Sadly, the east coast, lower midlands and Derwent Valley are struggling to desperate. 

The worm report is much the same as last month: Merino weaners are vulnerable unless you are one of the two people in the state who use smart grazing. Light Merino ewes are similarly vulnerable. Cross-bred (XB) lambs are likely exposed to high contamination if they are grazing grass-dominant circles (which they probably are because the clover and lucerne circles have just about shut down). XB ewes look excellent and are generally returning low worm egg counts (WECs).

Timing:  At an MLA/AWI co-event yesterday I delivered my usual spiel about the judicious use of long-acting (LA) drench products. They are beloved of Tasmanian sheep producers, and they make running Merino weaners through winter, and lambing, oh so easy. The thing is that they can contribute to drench resistance and the clients with the worse mectin resistance status are those who have had an unrelenting affair with long-acting products. The audience was a bit arms-folded, yeah-yeah, we’ve heard it all before. During question time a southern producer affirmed that he had used LA products for years, had great worm control but that the mectins were now essentially stuffed.

Thank you, Will, your timing was exquisite. Listen to him if not to me. There is nothing wrong with using an LA product if you really need to, but it ill-behoves us to use them so relentlessly that mectin resistance develops to the point that they do not work when they are needed. And for the record, rotating between moxidectin injectable and mectin-containing capsules is unlikely to significantly slow mectin resistance, as there is no break from this drench group.

So, in 2019: As indicated in the introduction,wormboss the winter is shaping as a grim affair in many parts of the state. So, to take a bite on the corncob, here are the suggestions for Tasmania for winter drenching.

• For areas north of Campbell Town the pastures and ewe body condition scores (BCS) look fair to good so you should not need an LA unless:
  • Pastures are currently less than 600 kg dry matter (DM) per hectare (Ha), and you have little chance to save adequate pasture for the lambing ewes.
  • Merino ewes BCS is currently less than 2.5, and you are or envisage feeding.
  • It turns horribly wet.
  • If any of the above occur, it’s a good year to use an LA of one form or another. Don’t forget priming and tail-cutter drenches (see WormBoss for the details).
• For areas south of Campbell Town the East Coast and the extended Derwent Valley: there is a good chance that one or all of the above points for the north already apply. It’s highly likely that you run the risk of a high worm year and so an LA is a good tool to consider.
• Most mobs of XBs are looking excellent, but consider an LA if yours are light (<2.5), and you anticipate pasture shortage at lambing (particularly, July/August lambers).
• If you have evidence of barber’s pole, and you are going to lamb down on barber’s pole (BP) infective paddocks, do 2 two things:
  • Spell the BP contaminated paddocks as much as possible in the run-up to lambing.
  • Consider an LA to break the BP cycle.  This is not an “every year” recommendation. BP has a greater propensity to develop resistance than any other species. (Closantel is also on the agenda, as a long-acting barber’s pole worm drench).

Cattle:  A reminder that the early winter drench for weaned calves should have been given by now. Most adult cattle are travelling well (CS>3). Also consider using an oral, non-mectin drench to give the mectin injectables and back-liners a rest.