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Victoria worm update - November 2012

Tricia Veale, Benalla (triciav7@bigpond.com)

The hot dry weather has now really switched on in this area of north-eastern Victoria.

There was 36 mm of rain for October and 16mm so far for November. The paddocks are rapidly drying off, many crops have been harvested and fortunately, most dams are still quite full.

Worm egg counts are generally at moderate to high levels as the residual underground moisture is allowing the immature worms to survive.

The purpose of the first summer drench is to eliminate worms inside sheep as the pasture dries off. If sheep are not drenched at this time, they will continually pass worms eggs which will contaminate the pasture and become the seeds for problems later on. The timing of this drench is important. In most years, it’s usually carried out in mid/late December.

This is the time to make sure that there are no large numbers of worms inside the sheep, as most of the larvae on the pasture will be soon killed by the ultraviolet light and heat of summer. This helps to bring about a natural break in the worm life cycle. So check the situation by getting some worm egg counts done.

Drenching sheep unnecessarily will only hasten the development of drench resistance on your property. This is because you kill all the susceptible worms, so that worms that are developing resistance to certain drenches survive in greater numbers.

So this is the ideal time to get a drench resistance test done on your youngest sheep. Knowing your drench resistance status is a good business strategy. I suggest that you now need to do such a test every 2–3 years to keep up with the resistance trends on your place.