The Department of Agriculture, Western Australia has imposed emergency temporary measures on the importation of wheat seed to prevent the spead of Wheat streak mosaic virus into Western Australia. 

Principal plant virologist Roger Jones said the entry of wheat seed into Western Australia was not banned, but some seed would be permitted under conditions approved by the Department’s Director General.

Dr Jones said the temporary measures would remain in place pending a detailed pest risk analysis (PRA) for Wheat streak mosaic virus to determine the risk posed by interstate movement of wheat seed.

As part of the PRA the Department has prepared a draft analysis of the major identified pathways for the entry of Wheat streak mosaic virus via wheat seed imported into Western Australia and will be seeking industry comment.

The virus threat and the proposed biosecurity measures will be discussed at the Department’s Agribusiness Cop Updates in Perth on 15-16 February.

Dr Jones said Wheat streak mosaic virus caused a disease that reduced the yield of wheat and damaged grain quality.  Wheat plants infected with it were severely stunted, and showed pale streaking and mottling of leaves.

He said the potential economic impact of the virus had increased dramatically with new information confirming the virus was seed borne.  In addition, tiny mites – morphologically identical to the virus vector wheat leaf curl mite – were found in 2005 in Western Australia's wheat growing regions. 

“Wheat streak mosaic virus has not yet been found in Western Australia, but is established in New South Wales, the Australian Capital Territory, Victoria, South Australia and Queensland,” Dr Jones said.

“The emergency measures were deemed necessary after a severe outbreak of the virus in NSW crops in 2005, clear evidence the virus is seed-borne in wheat, and the presence in Western Australia of mites similar to leaf curl mite.

“As the virus is not currently known to occur in Western Australia, preventing the virus from entering the State is the best means to minimise risk for the WA wheat industry.

“Should it become established in Western Australia, the greatest potential for damaging epidemics is with early sown wheat in high rainfall zones.  Northern areas could also suffer significantly as their warm autumn temperatures seem very suitable for the mite vector.” 

Dr Jones said currently, destroying the ‘green bridge’ between growing seasons, delaying sowing until winter and sowing healthy wheat seed stocks were the only management measures available. 

Chemical control is impractical and breeding of wheat with resistance to wheat streak mosaic virus was only in its infancy in Australia.