The Department of Agriculture and Food, Western Australia says the use of tested seed is important to protect crops from Wheat Streak Mosaic Virus (WSMV).

WSMV was found in self sown seed on several properties in the Esperance and Kondinin regions in April this year, and was identified for the first time last week in a sown commercial wheat crop in Merredin. 

Department of Agriculture principal plant virologist Roger Jones said farmers should be looking out for signs of Wheat Streak Mosaic Virus (WSMV), especially in early sown crops.

“The Department advises farmers to sow seed stocks from which a representative seed sample has been tested, and the sample found to be healthy,” Dr Jones said.

“Seed samples can be tested for the virus, and seed should not be retained from WSMV affected crops or where a seed sample tests positive,” Dr Jones emphasised.

“AGWEST Plant Laboratories confirmed the virus in the sown commercial wheat crop last week after testing a sample from the Merredin area,” Dr Jones said.

”Landmark consultant Scott Thomson sent the sample in on behalf of a grower who became concerned about an early sown wheat crop in which all the plants had pale green streaked leaves with yellowing of leaf tips and stunted growth,” he said.

Dr Jones said that in early sowing situations Wheat Streak Mosaic Virus could significantly reduce the yield and grain quality of wheat, although experience with the disease under Western Australian conditions was still very limited at this stage.

“Early sown crops are at higher risk because of the potential for the virus vector, wheat leaf curl mite, to be active in spreading the virus within the crop at young growth stages prior to cold winter months,” he said.

“The wheat curl mite vector survives the dry summer period in green bridge growth consisting of volunteer cereals and grasses.”

Farmers who suspect Wheat Streak Mosaic Virus in their wheat crops can send shoot samples into AGWEST Plant Laboratories for identification. 

Dr Jones said retention of seed grain from crops carrying the virus should be avoided at harvest.

“Because the virus is transmitted through wheat seed, the Department is currently developing a seed test, with support from the Grains Research and Development Corporation.” Dr Jones said.

“It is expected that an initial testing service will be available to farmers to test suspect seed stocks in time for next year’s sowing.”

Dr Jones said that unlike the situation with some aphid transmitted viruses, pesticides were not effective against the mite vector, and there were no known wheat varieties resistant to the virus.

“Ensuring sowing of seed stocks from which a representative seed sample has been tested and found free, and controlling the green bridge before planting wheat in paddocks are the only control strategies currently available,” Dr Jones advised.