Reliable eradication requires pesticide treatment of all sheep at shearing or within six weeks after shearing. Backline application should be applied on the day of shearing, if possible.
In addition, application at this time results in lower residues in next year’s clip because less chemical is used and the chemical has a longer time to degrade until the next shearing.
Off-shears backline treatment:
- use an insect growth regulator (Zapp, Magnum, Epic, Command, etc.)*
- use a diazinon off-shears backliner (for example, Eureka Gold)
Short wool dip up to six weeks, preferably two to three weeks off-shears:
- use an insect growth regulator (Fleececare, Strike, etc.)*
- use an organophosphate (Diazinon, Jetdip, etc.)
- spinosyn (Extinosad)
- magnesium fluorosilicate (Flockmaster II, Splash, etc.).
* There is some evidence of emerging IGR resistance.
Frequent and thorough monitoring for signs of rubbing should be undertaken after treatment. In May 2007, the use of diazinon as a dip was suspended. Only product bearing a label that includes the dip claim can be used. All new products omit this claim.
Some growers routinely treat for lice without knowing if lice are present, but chemicals should only be used when necessary, that is, when lice are found or suspected. Eradicating lice and preventing their reintroduction can achieve considerable cost savings.
Long wool treatment:
Org anophosphates, such as diazinon, are not registered for use in long wool for lice control. Before any treatment, the potential residue implications should be considered carefully.
Withholding Period/Export Slaughter Interval restrictions:
The wool harvesting interval (WHI), previously referred to as the wool withholding period (WHP), is defined as the time from application of a chemical to when the wool is shorn (also includes crutching).
Before applying a chemical, it is essential to check the Export Slaughter Interval (ESI) to ensure that it can be complied with. The ESI is the time from chemical application to when an animal is slaughtered for export.
Some producers have had sheep rejected at abattoirs due to insufficient time being allowed between treatment and slaughter. The meat WHP appears on the label but the ESI does not appear on labels of older products. All new products will include the ESI, however.
Abattoirs require the (longer) ESI to be complied with, as well as the meat WHP (the meat WHP relates only to the domestic meat market and is generally shorter than the ESI). Where the ESI is not on the product label, they can be found on the current version of the National Sheep Vendor Declaration.
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