The weed-munching insects have been flourishing in the western Wheatbelt, and have even spread successfully to drier areas as far east as Merredin, Mukinbudin and Corrigin.

Paterson’s Curse covers an estimated 10 million hectares across the southern states of Australia and costs farmers $300 million each year in agricultural losses.

The Department of Agriculture and Food has been working with the CSIRO and other states on establishing a suite of five biological control insects to control the weed, with support from Meat and Livestock Australia and Australian Wool Innovation.

Department senior technical officer Paul Wilson said he had been surprised by how far the biological control agents had spread and how effective they had been in some cases.

“We know they are established in the west agricultural area, but we are now getting reports from the eastern Wheatbelt, as far east as Merredin, Mukinbudin and Corrigin where we were not confident that they would survive due to the drier conditions,” Mr Wilson said.

The collaboration first started importing the biological control agents 20 years ago from France, including the leaf mining moth, crown boring beetle, the root boring weevil, the flea beetle and the pollen beetle.

Later another strain of the crown boring weevil was imported from Portugal, which was better adapter to dryer parts of Australia including much of WA.

Extensive testing was undertaken before the insects were released to ensure they did not pose a risk to any crops, native or introduced plants.

The Biological Control Program will slow down in June 2010, after which time the insects should be established well enough to spread naturally.

Until then, landholders interested in having biological control insects dispersed on their property should contact local departmental biosecurity officers.