by Lewis Kahn, Executive Officer, ParaBoss
Following on from previous articles about worm and blowfly control practices, the lice control practices used by Australian sheep producers in 2011 are summarised in this article. These control practices were collected from the national survey conducted by Professor Steve Walkden-Brown and Dr Ian Reeve from the University of New England, which was supported by Australian Wool Innovation Limited and Meat and Livestock Australia.
Lice infestations remain a concern for Australian sheep producers with detection of lice being reported by 23% of producers in 2011 with a further 27% reporting rubbing (Figure 1). Rubbing can be caused by a number of factors other than lice, including grass seeds, itch mite and wool breaks. The LiceBoss Rubbing Tool helps producers to determine the probability that rubbing was due to a lice infestation. It’s likely the increased detection of lice infestations is due to treatment failure associated with the development of lice populations resistant to synthetic pyrethroids and/or insect growth regulators.
Twenty six percent of producers reported they suspected resistance to lice treatments on their property with the majority of suspicions for the effectiveness of products from the insect growth regulator group (e.g. triflumuron and diflubenzuron). While some sheep lice populations have developed resistance to synthetic pyrethroids and/or insect growth regulators, treatment failures are also due to incorrect application or under-dosing. If resistance is suspected, do not use products belonging to that group of pesticide. If lice are resistant to any product, then resistance will apply to all other products belonging to the same pesticide group.
Lice prevention remains a major strategy used by sheep producers and this is likely the reason why 22% of producers had no lice treatment in the period 2009–2011, yet over 50% of producers reported no evidence of lice for the same period. This also indicates producers are concerned about the biosecurity of their property, or with the effectiveness of their chosen lice treatment, or are not confident in detecting lice and would rather treat. Backliner treatments were the most frequently used control technique for both short and long wool treatments (Figure 2).
Lice prevention involves an integrated approach to management, including preventing new infestations from strays and purchased sheep, where possible avoiding split shearings and careful choice of products and treatment methods when treating lice in ewes within six weeks of lambing. Advice about these preventative measures is contained in LiceBoss as are a number of decision-support tools to improve the chance of lice eradication and compliance with wool and meat residues.
Short wool backliner treatments included insect growth regulators (47% of producers that used a short wool treatment), neonicotinoids (33%), spinosyn (26%) and organophosphate (21%) pesticide groups (note that percentages can sum to more than 100 as producers may have reported using more than one product). Short wool treatments applied using plunge or shower dips were characterised by strong reliance on organophosphate (60–80% producers) and spinosyn (10–15%) pesticide groups.
Of those producers that used a long wool treatment, backliner treatments using spinosyn and synthetic pyrethroid groups were used by 74% and 11% respectively and jetting using macrocyclic lactone and spinosyn pesticide groups by 48% and 30% respectively.
Backline treatments, used off-shears, can be a relatively quick and easy method of treating sheep to eradicate lice, but they require care during application to obtain good results. Most products must be applied within 24 hours after shearing and some up till seven days after shearing. As with all lice control treatments, it is essential that every sheep is treated according to the label directions for dose rate and application pattern.
The LiceBoss website can help advise on the three main elements of lice control: preventing new infestations, structured monitoring to detect infestations and strategic use of chemical treatments. The LiceBoss Tools provide decision support for
On a final note, 3% of sheep producers had used LiceBoss to make a change to lice control and another 13% had visited the site. But we have to do better because 35% had heard of LiceBoss but not visited the site and a further 49% of producers had not heard of LiceBoss. Even though we have nearly 1,000 people visit LiceBoss each month, it is clear that we need to keep spreading the word.