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Western Australia worm, flies and lice update - April 2014

Albany: Brown Besier, DAFWA (brown.besier@agric.wa.gov.au)

The recent good rains throughout most agricultural areas of the state have ended the long dry period, with increasing pasture (and weed) growth. This also means the start of the sheep worm year.

It is essential that sheep are not putting out significant numbers of worm eggs in May, as with cool conditions and some moisture at pasture level, a large percentage will develop to the larval stages. The numbers of larvae picked up as sheep graze determines the extent of worm problems in winter and spring.

All sheep on the farm should have low worm burdens at present. Weaners and hoggets should have received a drench in summer, and older sheep either a drench in autumn (late March– early April), or been shown to have low worm egg counts. Provided the drenches were effective, the farm is then set up for manageable worm burdens later in the year, although monitoring is always needed.

Worm egg counts should be checked in mobs that were not drenched in the last few months, or where there is a query over drench effectiveness.

It is especially important to check worm egg counts in ewes ahead of lambing, so lambs are not exposed to heavy worm challenge. Ewes given an effective drench in autumn will generally have low counts and not need a pre-lambing drench. Where no autumn drench was given, worm egg counts should be monitored or a pre-lamb drench given.

We can no longer assume that the widely-used ML drenches (macrocyclic lactones, abamectin and moxidectin) will be fully-effective, as resistance to this group continues to increase. It is also wise to check counts where the ‘triple combination’ drenches are used, as although they are more likely to be fully-effective, resistance has been detected in a few cases.

Once pasture growth is well-established, worm eggs and larvae develop well, and worm control is based on checking worm egg counts. Getting worms under control before then is a good investment!

Esperance: Nicole Swan, Swan’s Veterinary Services (nicole@swansvet.com)

We have still had no rain at the point of writing. Unlike most years when we get consistent summer rain this year has been dry. As a result, perennial pastures are dormant, feed is getting low and worms have not been a problem.

Recent counts have in general been low and few properties need to drench prior to the break. For coastal properties with a history of barber’s pole it is recommended that ewes are drenched with closantal closer to lambing, as a rainfall event could result in barber’s pole becoming a problem during lambing.