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Get rid of virus host plants
Queensland, Australia
April 13, 2004

Farmers need to make sure their winter cropping areas are free of host plants to reduce the risk of crop damage from two recently discovered plant viruses.

Queensland Department of Primary Industries plant pathologist Emma Colson said both the wheat streak mosaic virus and the recently discovered high plains virus were spread by the same insect, the leaf curl mite.

She said this meant that eradicating host plants would help stop the spread of both viruses.

Dr Colson said the viruses could survive on volunteer plants of wheat and summer cereals, cereal plants such as maize and host grass weed species.

"Sorghum is considered a host plant in the United States and DPI&F research later this year will determine whether this is so in Australia."

She said virus management should involve:

  • spraying out or cultivating green summer crop stubble and grass weed hosts at least two weeks before planting wheat

  • controlling volunteer winter cereal plants during fallow

  • controlling grasses in fallow

  • controlling grass weeds on crop borders.

Spraying mites with pesticides did not effectively control them.

Dr Colson said the high plains virus was a relatively new disease of cereals, first discovered in 1993 in maize and wheat crops on the High Plains of the United States.

It was thought to be widespread throughout the world but had been undiagnosed because of the complexity of developing an appropriate test. The DPI&F virology laboratory had developed a test with financial support from Plant Health Australia.

She said host plants included maize, wheat, barley, oats, rye and some grasses.

Symptoms were stunting and yellowing, and mosaic patterning on the leaves of infected plants.

Dr Colson said leaf curl mites carried the virus from infected plants to healthy plants, travelling by wind and on clothing, animals and vehicles.

She said mites needed a continuous "green bridge" of alternative host plants to survive between crops. Removing all host plants for at least two weeks between crops could disrupt their life cycle.


Dr Colson said the commercial importance of high plains virus in Australia was not yet known.

"We believe its effects will be similar to those of wheat streak mosaic virus that caused some yield loss in a small part of the wheat crop on one of the two commercial properties on which it was found.

"Losses were minimal in the other commercial crops around Australia where wheat streak mosaic was found."

She said testing was continuing on other plant material for high plains virus, including any that had shown symptoms of wheat streak mosaic virus last year but which previously tested negative for that disease.

The DPI &F will soon be posting information on wheat streak mosaic virus and high plains virus to all Queensland wheat growers. Information is also available from the DPI Call Centre (13 25 23) and from the DPI website.

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