How much power is left?

Think of a drench family like a battery. When you first use it, it is fully charged and kills all the worms in a mob. Over time and with more uses the drench loses it’s charge and kills fewer worms. A number of factors influence the speed of this reduction in power such as: underdosing, timing and frequency of treatment and persistent use of ineffective drenches.

Drench resistance starts to develop from the first time a drench family is used on a property. Some worms are able to survive the drench and some of their offspring will be resistant. Every time that family of drench is used, the number of surviving worms will increase and with continued use the proportion of resistant worms will gradually increase.