TURNIP YELLOWS VIRUS (TUYV) (SYNONYM: BWYV)

This is the most important virus of oilseed rape and canola crops in Australia. The virus is wide spread throughout Australia and in 2014 emerged as an epidemic of canola crops in South Australia, destroying thousands of hectares. This virus is transmitted by several aphid species, but the green peach aphid is the most efficient vector. To date, no resistant varieties are available.

What to Look For

Infected canola crops show a variety of symptoms but also can be symptomless. Symptoms include reddening of leaf margins and interveinal chlorosis, (Figure 10.24). Infected plants may be dwarfed, leaves may be thicker, leathery, yellow and brittle. The early infected plants are killed.

Figure 10.24 BWYV symptoms in canola

Disease Cycle

The virus and aphid vectors persists over summer in fodder turnips and in weed species, then aphids transfer virus into canola crops in the winter. TuYV is not seed-borne. Annual sampling of green peach aphid populations have shown that up to 72 percent of winged aphids carry TuYV. The virus is phloem limited; aphids need to ingest infected sap to acquire the virus.

Virus Management

To date, virus resistant varieties of canola are not available so integrated management practices are advised. These include, weed control, removal of green bridge during summer, sowing into standing stubbles, the use of neonicotinoid insecticide seed dressings and in-crop aphid control based on monitoring.

CANOLA VIRUSES

TURNIP MOSAIC VIRUS (TUMV)