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Tasmania worm, flies and lice update - May 2014

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

In the last month there has been moderate to good rainfall over most sheep grazing areas. Nearly all paddocks have good feed availability, and pastures are growing strongly as the weather remains unusually warm. These conditions favour worms to a T: to date the worm situation has remained relatively good with WECs generally modest. This is due, in part, to the fact most prime lambs have been finished or sold as stores. The exception is merino weaners where egg counts seem to be rising rapidly. No surprise, really.

Clients often refer to moving their sheep to a ‘fresh’ paddock: a bit like grandad ‘taking the airs’. Most fresh paddocks have additional feed, but rarely if ever offer any parasitic security. The notion that spelling a paddock for a month substantially reduces the available worm burden persists. This is fallacious and risky.

In Tasmania, it is rare, even in summer, to have rapid environmental pasture decontamination. Indeed, the most rapid larval death may occur during the spring when activated larvae use their energy reserves and die. Moreover, they may be effectively diluted by large volumes of pasture.

‘Clean’ pastures require long periods without additional contamination. We’re talking 4–6 months. The ‘no contamination’ means total spelling, grazing with cattle or grazing with sheep or goats within 3 weeks of a working drench (smart graze). Cropping paddocks, new pastures and fodder crops generally fit the bill, sometimes with less than 6 months spell due to cultivation. Hay paddocks are frequently a trap. There is much talk of a vacuuming effect, but this only occurs when there are high stocking rates and little pasture (e.g. preparing smart graze paddocks).

The purpose of this rant is that you need to start planning your weaning paddocks now. Putting freshly weaned lambs on to pasture grazed a month previously by ewes and lambs will hardly do.

May and early June are frequently mild enough to permit plunge dipping for lice. In the opinion of this correspondent, this still gives the best chance of eradication. Wind and rain are the killers, so choose days with a frosty start created by the famous Mike Pook’s equally famous blocking highs. While some dips were decommissioned due to arsenic and OC contamination, many fell in to disuse through the monumental convenience of backliners. Many of the latter can be resurrected with little work. The alternative is a mobile ‘fish and chips’ dipper. There is one operating in Tasmania. Contact me for details.