Wheat streak mosaic is caused by Wheat streak mosaic virus (WSMV) which is transmitted by the wheat curl mite (Aceria tosichella). The two main symptoms of wheat streak mosaic are leaf mottling (mosaic) and leaf streaking, first appearing as light green streaks running parallel to the leaf veins; then turning yellow and developing into blotches.
As the wheat curl mites feed on the crop, they can cause additional damage, with leaves curled upward and inward, sometimes trapping new leaves or the emerging head and resulting in rolled, twisted plants. These symptoms can be confused with nutritional disorders, environmental effects and chemical damage. Laboratory tests are needed to positively identify WSMV.
Currently the most useful methods for Australian growers to control wheat streak mosaic are to break the disease cycle and control the grasses that the mites survive on between crops.