Australian citrus growers in the Riverina district of New South Wales have taken fruit fly control into their own hands by purchasing an electronic road sign to warn approaching motorists to dispose of any fruit they may be carrying.

Funded by Riverina Citrus and Griffith District Citrus Growers, the sign cost A$26,000 and will be housed by the New South Wales Department of Industry and Investment, the Weekly Times reported.

Riverina Citrus executive officer Scot MacDonald said although the sign was expensive, growers had been happy to support it.

'The flashing sign will warn motorists they are entering a fruit fly exclusion zone and will be fined if they don't dispose of their fruit,' he said.

Mr MacDonald said the road sign, along with a tripling of roadblocks, was part of a concerted effort to prevent future outbreaks of Queensland fruit fly, and to protect lucrative export markets.

'We are demonstrating to our export customers that we are serious about this and it is important if we want greater international access for our fruit,' Mr MacDonald said.

New South Wales fruit fly exclusion zone boss Maryanne Nolan said an outbreak would put 'millions of dollars of industry at stake'.

Roadblocks began operating in the Riverina before Christmas and will continue throughout January.

On Tuesday 12 January, a single female fruit fly was trapped across the Victorian border in the town of Mildura, prompting the introduction of a 15km-radius exclusion zone whereby all fruit leaving the area must be certified.