Beet western yellows virus (BWYV)
Hosts
BWYV is also known as turnip yellows virus (TuYV). BWYV infects all vegetable brassica crops, canola and brassicaceous weeds. It has a very wide host range, including many other non-brassica crop plants and weeds from a range of plant families.
Distribution
BWYV is distributed throughout temperate regions of the world. In Western Australia, it commonly infects canola crops but may also be found in vegetable brassica crops. Wild radish is a key host and acts as a reservoir for the virus. Many non-brassica crops and native plants can also become infected, acting as reservoirs for spread to brassica species.
Symptoms
The virus causes reddening of lower leaves and plant stunting, resulting in reduced yield. Its symptoms are easily confused with those of nutritional imbalance, herbicide spray damage, waterlogging or other stress factors. In cabbage, BWYV also induces tip burn in internal leaves, particularly during storage.
Spread
BWYV is spread predominantly by the green peach aphid which colonise brassica crops. Once an aphid is infected with BWYV, it transmits the virus for the rest of its life, so it is important to control aphid populations. Most populations of the green peach aphid in Western Australia are resistant to ‘old chemistry’ insecticides.