Drenching is expensive and time consuming so pre-drench faecal egg counts (FECs) should always be considered, and this will put some science and evidence into whether or not to drench.

Strategic summer drenching involves an effective drench at the beginning and end of the season. This is to take advantage of the destruction of worm larvae on pasture by heat and lack of moisture.

The life cycle of the worm involves both your pasture and the animal, whereas the drench fixes the animal problem, the hot, dry conditions of summer helps to eliminate the pasture problem.

 Some regions in Victoria early this season, experienced unseasonably wet weather.

This may have led to conditions in which worm egg and larvae survival on pasture was greater than normal, therefore reducing the effectiveness of the first summer drench.

In addition, ineffective chemicals and/or an inadequate drench procedure will reduce the effectiveness of summer drenching.

Worm resistance, particularly to the white and clear drenches, is common in north east Victoria and unnecessary overuse and the incorrect use of drenches just add to the problem.

After drenching, producers should try to put sheep onto low-risk pastures; these may be paddocks previously grazed by cattle, cut for hay or silage or grazed by low-risk sheep such as older wethers.

Ewes rearing lambs and the lambs, particularly after weaning, are the most susceptible sheep in terms of worm burdens.

Large reinfestations of worms can occur in as little as three weeks if your drenching program is ineffective.

For further advice contact your local veterinarian or Agriculture Victoria veterinary or animal health officer, or in NSW your Local Land Services.