Spring is a busy time in the sheep and wool industry’s calendar, with many of your customers shearing, crutching and applying treatments for the prevention or control of lice, blowfly strike and worms.
Product stewardship is everyone’s responsibility, and this is the perfect opportunity to encourage your customers to adopt best practice guidelines to ensure optimal results and to protect the efficacy of all available chemistry.
It’s important to take a holistic approach when recommending lice, blowfly and worm control products. This is because many modes of action are used to control different target species.
For example, neonicotinoids (e.g. imidacloprid), spinosyns (e.g. spinosad), macrocyclic lactones (e.g. ivermectin) and organophosphates (e.g. diazinon) are widely used to control sheep lice and to prevent or treat blowfly strike. Macrocyclic lactones – also widely referred to as ‘mectins’ or MLs – are used to control worms.
Resistance may develop to any chemical if it is used continuously. Australian sheep and wool producers have relied upon neonicotinoids and spinosyns for the last decade as their ‘go-to’ pour-on lousicides.
While there is no known resistance in Australian sheep lice populations to these two important modes of action, it’s important that we keep it that way. If your customers have been using imidacloprid or spinosad products for several years, it’s time to rotate to another effective mode of action.
The mode of action selected for lice control will also affect treatment options for blowfly prevention and control. Lice are obligate parasites that remain on host sheep throughout their life cycle. This means that any lice present in the fleece will be exposed to any blowfly strike preventative or treatment applied later in the season.
Industry guidelines discourage the consecutive use of lousicides with the same mode of action, or the use of the same mode of action for lice control and flystrike prevention in the same season.
Put simply, if a neonicotinoid or spinosyn is applied to control lice, the same mode of action should not be applied to prevent blowfly strike during the same wool growing season.
Annual product rotation is arguably less important when selecting a blowfly preventative. Unlike lice, blowflies are dormant over the winter months and are therefore not exposed to chemical treatments during the pupae stage of their life cycle.
The onset of widespread resistance to cyromazine and developing resistance to dicyclanil poses a serious concern to the industry.
Whilst resistance to chemical treatment can result in a reduced period of protection, it is worth remembering other factors, such as incorrect application technique or adverse environmental conditions during or after application, also reduce the protection period.
Dicyclanil based products will continue to provide trusted and reliable protection against flystrike for the vast majority of your customers, provided they are applied in accordance with the label directions.
Likewise, best practice guidelines for worm control should be considered when recommending a pour-on lousicide containing abamectin. There is widespread resistance to all older active ingredients found in sheep drenches, including macrocyclic lactones.
Industry guidelines recommend conducting a Worm Egg Count to determine worm burdens before drenching. If the worm burden doesn’t warrant drenching, then don’t!
If drenching is required, it is recommended to use a ‘fully effective’ drench and ideally, as part of a combination drench.
Regardless of which products you recommend, good application technique is essential to achieve effective prevention or control of parasites. Remind your customers to always read and follow the label directions and to visit paraboss.com.au for industry recommendations for effective lice, fly and worm management.
By Dr Kathryn Humphries, senior brand manager at Elanco Australasia.
Drenching best practice:
• Test and monitor drench efficacy regularly
• Only use ‘fully effective’ drenches
• Use combination drenches wherever possible
• Only use long-acting products during high worm-risk conditions and in combination with a primer/exit drench
• Quarantine drench all introduced/returning sheep with four active ingredients (including monepantel or derquantel)
• Incorporate grazing management to create ‘low risk’ pastures
Lice control best practice:
• Do not apply the same mode of action consecutively
• If consecutive use of the same mode of action is required, careful attention should be paid to achieving eradication after treatment
• Sheep that require treatment with a long wool lousicide should be re-treated with an off-shears lousicide at the next shearing
• Do not apply the same mode of action for lice control and flystrike prevention in the same season
• All lice treatments should be applied as part of an integrated pest management program, including good fencing, mustering, shearing and application technique
Blowfly prevention best practice:
• Use a high concentration dicyclanil formulation
• Apply dicyclanil products early in the season (depending on time of crutching and/or shearing)
• Always use the recommended application technique
• Only use short-acting dicyclanil products when a shorter withholding period is required
• Do not apply the same chemical mode of action for blowfly strike prevention and lice control in the same wool growing season
• Stop using cyromazine to reduce selection pressure for dicyclanil resistance
