Wheat streak mosaic virus and the wheat curl mite

The first known case of Wheat Streak Mosaic Virus (WSMV) has been found in Tasmania. This discovery means this damaging virus has now been detected in all major cropping regions of Australia, and serves as a timely reminder to be on the lookout for WSMV. In previous years, symptoms have been apparent from late August onwards. Agronomist, Paul Parker (NSW DPI), says that although many crops are suffering severe moisture stress, monitoring remains important. Paul says that in areas such as the Liverpool Plains district of NSW and the Western district of Victoria - where crops were sown on time and yield potential remains high - agronomists and growers should keep a close lookout.

WSMV is primarily spread by the wheat curl mite (Aceria tosichella), although low level transmission can also occur through infected wheat seed. Recent research at cesar has identified the presence of wheat curl mite in Tasmania, with a distribution that broadly covers the north-west and the eastern part of the state. 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.

The wheat curl mite is widely distributed in south-eastern Australia and can survive on plants other than cereals. Alternate hosts identified in Australia include barley grass, great brome, annual ryegrass, cocksfoot, black oats, prairie grass, hairy panic, soft brome, wild oats, winter grass and rat’s tail fescue. At this stage, controlling these host plants (which can provide a “green bridge” between seasons) is likely to be one of the most practical methods to reduce the build-up of mite numbers and the risk of WSMV.

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

If you observe any symptoms that resemble wheat streak mosaic virus, contact your local agronomist or Paul Parker on (02) 63821077 or by email: paul.parker@dpi.nsw.gov.au.