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Beyond the Bale : September 2016
Early season flystrike prevention is an underutilised strategy that can decrease both the incidence and the overall cost of flystrike, as well as improve sheep welfare. It may also use less chemical throughout a fly season. The early season flystrike prevention strategy involves applying a long-acting flystrike preventative to the whole flock before any fly activity in spring, followed where possible, with shearing or crutching when the chemical protection period is ending. This prevents a fly population from building up after a winter dormancy, so that strike is ultimately prevented later in the season by a lack of flies, rather than by making sheep less susceptible or applying another chemical treatment. WHEN IS IT WARRANTED AND SUCCESSFUL? 1. This strategy is only warranted on flocks in high rainfall areas where producers already need to treat most mobs or the entire flock for flystrike in most years. If this strategy is not suitable for you, other methods for choosing the right treatment time can be found on the FlyBoss website. 2. Winter daily maximum air temperatures must drop below 16°C for most days in an 8-week period to provide a complete break in the fly season. In these circumstances, no adult flies are present during winter, but the parasite survives to the following spring by overwintering as 'arrested' larvae in the soil. 3. Proximity to neighbouring properties where sheep could be/have been flystruck could compromise effectiveness of the strategy. While Lucilia cuprina can travel up to 10km or more, flies coming from within a few kilometres pose the most threat. 4. All sheep on the property must be treated. This may preclude the strategy from properties where some sheep, such as lambing ewes, cannot be mustered and treated when required. 'Covert' strikes (ones that cannot be detected easily on general inspection) in untreated sheep are not uncommon, and they are an important ongoing source of maggots that build up the fly numbers through a season. 5. The method may not be cost-effective if shearing or crutching is carried out in the first 3 months of the fly season because any protective chemical will be removed and a new protective treatment must be applied immediately after shearing or crutching. WHAT DOES IT INVOLVE? Early season flystrike prevention involves application of a flystrike preventative chemical to all sheep before any flies have emerged after winter, to prevent any successful breeding of flies from spring to mid-summer. Treatment must be applied to both the body and the breech. The treatment, which should contain either dicyclanil, cyromazine or ivermectin, is generally applied in August to October, before flies emerge on that property. Fly- trapping or previous experience can be used to plan when treatment should be applied. If the FlyBoss Optimise Treatment tool is used, then treatment must be applied several weeks before the tool suggests that any flystrike is expected. If shearing is typically done during summer, if possible, time it to occur just before the residual chemical runs out, to extend the period when strike cannot occur; shorn sheep Table 1: Maximum protection periods for recommended chemical actives *Actual length of protection on your property may be shorter and could be influenced by how well you apply the chemical, wool length at application, rainfall amount and intensity during the protection period, and the amount of urine stain, dag and fleece rot where the chemical is applied. Chemical active Application method Maximum protection period against flystrike* Wool Handling Interval Withholding Period (meat) WHP Export Slaughter Interval ESI Cyromazine 60g/l Spray on 77 days (11 weeks) 60 days 7 days 28 days Cyromazine 500g/l Jet or dip 98 days (14 weeks) 60 days 7 days 21 days Dicyclanil 50g/l Spray on 336 days (24 weeks) 90 days 28 days 120 days Dicyclanil 12.5g/l Spray on 77 days (11 weeks) 30 days 7 days 21 days Ivermectin 16g/l Jet or dip 84 days (12 weeks) 42 days 7 days 7 days EARLY S FLYSTRIKE P ON FARM
In the Shops - September 2016