With the unseasonably warm weather experienced earlier this month, some farmers may have already seen populations of biting and nuisance flies in herds of dairy and beef cattle they’d normally associate with much later in the year.  Now is the time to assess fly control options for the coming season, and choosing the right product will have a major impact on the effectiveness of any control strategy.

The extent to which a product controls flies depends greatly upon the choice of active ingredient within the product, with some ingredients proven to be more effective against flies than others. The product of choice this season should be one that is based on deltamethrin, since this is highly toxic to flies – it kills them on contact – and it has a very good margin of safety for mammals.  When used as a pour-on, deltamethrin provides more potent fly control than injections, ear tags and sprays. The graph below demonstrates the superior properties of deltamethrin as an insecticide over and above some other commonly-sold ingredients.  Intervet’s Butox SWISH contains a unique micronised form of deltamethrin which offers two months’ control of both nuisance and biting flies.

Other equally important factors that will determine the success of a fly control programme include treating early, before flies become a problem, and reducing the number of fly breeding and resting sites on and around the farm by treating with environmental control agents. 


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