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Tasmania worms, flies and lice update - August 2014

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

What a difference a few weeks make. Where, last week I was embarrassingly bogged to the diff, this week I could drive with impunity. Lambing is well underway in prime lamb mobs and most Merino mobs will kick off within 2 weeks. Ewes are in excellent condition and going on to requisite pasture quantities.

Egg counts continue to show the dichotomy of the last few months: XB ewes are fat and shedding few eggs; Merinos, particularly weaners, have returned some very high counts. After last month’s missive some Merino clients have opted for long-acting products for both Merino ewes and weaners, a few have yet to make the decision. The upside of using a long-acting after mid-August is that it frequently does away with the need for a weaning drench for the ewes. Monitor before going down this path. Only in the most extreme situations should weaners and hoggets need a long-acting product in September.

August through October is time for the great conversion: not from AFL to rugby (although a few Tasmanians would appreciate access to a few rugby games without hopping on a plane), but from worm vulnerable to worm resistant in 1yo sheep. The thing is that it will not occur if the weaners/hoggets have no worms, so the almost magical transformation to “dry-sheep resistance” will not occur if weaners are under the influence of capsules. It’s a balancing act: you do not want young sheep to succumb on contaminated pastures, nor do you want to delay the onset of immunity. As a generalisation I suggest that the egg counts be allowed to run up a little bit, provided the weaners have reasonable body weight and adequate pasture. Where Merino weaners would normally be drenched at a trigger of 300 epg, I might let them run to 400–500 with the stated provisos. As always, monitor very closely, and keep in mind what will be grazing those paddocks in the late spring and early summer.