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Wheat curl mites and WSMV

Growers should remain on the look out for wheat streak mosaic virus (WSMV) in wheat and barley crops for the remainder of the season. Fortunately there have been low instances of WSMV this year, however isolated cases of heavily infected wheat crops have recently been reported near Cobram, in the Northern Country district of Victoria.

Plants infected with WSMV initially have light green streaks on the leaves, which later develop into yellow stripes running parallel to the leaf veins. Symptoms can be difficult to detect in young plants and may sometimes be confused with nutritional, environmental or chemical effects. However, as plants mature the signs become more pronounced and affected plants can die prematurely, become stunted or fail to grow. Heads on infected plants can be sterile and contain no seed, or can contain small, shrivelled grain.

The primary vector of WSMV is the wheat curl mite (Aceria tosichella), a wingless, cigar-shaped mite, approximately 0.2 mm in length. The mite’s tiny size and secretive habits make it extremely difficult to detect even with a microscope. They live (and are protected) within leaf whorls, which means chemical control of wheat curl mites is largely ineffective. Alternate plant hosts 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. Controlling these host plants outside of the growing season is one of the most practical methods to reduce the build-up of mite numbers and the risk of WSMV in cereal crops.

As part of a GRDC funded project, Dr Adam Miller (The University of Melbourne) will continue to provide a free WSMV genetic screening service for growers this season. For further information, contact Adam on 0488 735 482 or via email at admiller@unimelb.edu.au

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

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