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Tasmania worms, flies and lice update - September 2016

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

As the year (and the years) roll inexorably forward things are looking rather sweet in Tasmania. Most areas have received better than 30mm from the tail end of the biblical rain that devastated western Victoria in the middle of the month. The north of the state is (again) very wet. The southern Midlands and Derwent Valley are just right, thank you. Grass is growing, and along with it the lambing mobs are doing well.

Things are quiet on the worm front. There have been few WECs on which to base any seasonal outlooks. For most producers the next issue is the weaning drench. The weaning drench is a given for all lambs and for ewes that are going back on to perennial pastures. Big, fat XB ewes that are being sent bush, or doing crop clean-up duties need not be drenched. For ewes going back to perennial pastures the drench is necessary as a first summer drench.

It’s timely to discuss drench choice and drench rotation. In times past the weaning/first summer drench was when producers rotated from one drench group to the next, and stuck with that drench for a calendar year. Current thinking (with a deal of good information to back it) is that the cross protection provided by combinations do a great deal more to slow resistance than rotation between groups. In the Tasmanian context this means that most drenches should be abamectin triples.

Do not forget the new compounds: Zolvix® (monepantel) and Startect® (derqantel/abamectin). In theory we should use these compounds in combination. In essence, use one or both once a year: weaning/first summer drench is a good time to use the new chemicals. Beware that Zolvix has a long ESI.

Given it’s so wet, we will only need a handful of warmer days to kick-start a good fly season. Modelling by Tasmania’s own Brian Horton suggests that Tasmania is not generally a good bet for suppressive fly treatments (i.e. using Clik in advance of the main fly wave similar to strategic drenching). However, earlier-than-normal treatments may be needed. Lambs normally shorn mid- to late-summer will be at risk. Give me a call if you need to nut-out an individual programme.