Backline treatments are very popular because of their ease of use, but to achieve good effect, careful application is critical.
Relatively small volumes of product are applied along the backs of the sheep from head to rump. From here, the chemical spreads over the surface of the body, assisted by contact between sheep.
Dose rates should be calculated according to the weight of the heaviest sheep.
Label directions stipulate the use of compatible applicators that must be checked for proper operation and accuracy.
Chemicals available for application by this method include insect growth regulators, synthetic pyrethroids, diazinon, imidacloprid, abamectin and spinosad. Further product information can be found in the LiceBoss Products Tool.
To effectively use backliners, see Off-shears backline treatments.
In this method of treatment, sheep are completely immersed in dipping solution. Effective lice control relies on sheep being wet to skin level over their entire body; this can be very difficult because of the waterproofing effect of wool.
There are several types of swim-through ‘plunge’ dips in which sheep must swim the length of the dip to exit. During the swim, it is recommended that sheep be individually ‘dunked’ twice to wet their heads. Dipping is a labour intensive operation, but an efficient operator with other staff can treat several thousand sheep per day. Plunge dips range from traditional in-ground, straight dips to mobile dips that are ‘U’ shaped.
There are also several types of ‘cage’ dips; most are operated by contractors. In cage dipping, groups of sheep are held in a lidded cage that is completely submerged in the dip solution. Movement of the cage and lid is controlled hydraulically and cage dipping can often be a one-person operation.
Some compounds used for dipping are subject to ‘stripping’. This is when the dipping chemical is removed or ‘stripped’ from the dip at a faster rate than dip wash, leaving a lower concentration of active compound.
Labels for products that strip include instructions for reinforcement and replenishment (topping up) to maintain adequate concentrations of pesticide in the dip wash. It is important that these terms are understood and that the label directions are followed.
Detailed information is available here: Plunge and cage dipping.
When you are concerned about spreading ‘dermo’ during dipping, with some products zinc sulphate can be added to the dip wash. For details, see Avoid dermo at dipping.
Shower dipping or ‘showering’ relies on applying a high volume of dip wash from spray nozzles on a slowly rotating boom to completely wet the sheep.
Shower dips need to be correctly set up according to the manufacturers instructions and be working efficiently. This includes correct horizontal boom rotation speed, effective nozzles, large volume pump delivery, adequate sump volume and use of the top sprays only.
Sheep must be showered for at least 12 minutes to achieve lice eradication.
It is extremely common to find that shower dips are not working properly.
Directions for optimal setup and operation of shower dips are given in Shower dipping.
Hand-jetting is one method used for applying a lice treatment in long wool (greater than 6 weeks wool growth).
Importantly, hand-jetting requires high pressures at the hand-piece for the liquid to penetrate the wool.
For complete directions on ensuring that your equipment works effectively, refer to Hand-jetting sheep for lice.