Wheat streak mosaic virus and wheat curl mites

Agronomist, Paul Parker (NSW DPI), has reported a case of wheat streak mosaic virus (WSMV) in an early sown wheat crop south of Harden, in the South West Slopes district of New South Wales. Paul says infected plants were mostly along one edge of the crop, adjacent to a flow line that was sprayed out prior to the crop being sown. The crop has been grazed with sheep this season. Agronomist, Graeme Callaghan (Graeme Callaghan & Associates), has reported wheat crops infected with WSMV north of Warren, in the Central West Slopes and Plains district of New South Wales. There has also been an unconfirmed report of WSMV in a 400 ha paddock east of Coonamble, also in the Central West Slopes and Plains district of New South Wales.

WSMV has been detected in all major cropping regions of Australia. Plants infected with WSMV initially have light green streaks on the leaves which later develop into discontinuous yellow stripes running parallel to the leaf veins. These symptoms can sometimes be confused with nutritional, environmental and chemical damage. Affected plants can die prematurely, become stunted or fail to grow. WSMV is a particular concern for early sown dual-purpose wheat crops, although it can also adversely affect main season sown wheat.

WSMV is primarily spread by the wheat curl mite (Aceria tosichella), although low level transmission can also occur through infected wheat seed. Wheat curl mites typically colonise the youngest tissue of a wheat plant and acquire WSMV when feeding on infected plants. Chemical control of mites is believed to be largely ineffective as they predominantly live (and are protected) within leaf whorls.

For further information on the wheat curl mite and WSMV, click here.