Green peach aphid and beet western yellows virus
What is BWYV?
BWYV infects the phloem (the living tissue that carries organic nutrients to all parts of the plant where needed) of plants and is persistently transmitted by aphid vectors. BWYV infection can result in significant losses in seed yield and oil content. Symptoms may initially resemble nutrient deficiencies, herbicide damage, physiological stress or other disorders. Leaves may turn yellow and purple, starting from the lower leaves. Other symptoms may include leaf mottling, leaves becoming thickened and cupping inwards, and premature bolting.
Canola is most susceptible to BWYV at the rosette stage, when infection can lead to high yield losses. Generally, the yield consequences of BWYV decrease with infection at later stages of crop development. However, canola can remain susceptible to yield losses from BWYV infection until approximately the mid-podding stage. Infection after this stage usually results in minimal yield loss but oil quality can still be affected.
Green peach aphid is the most important vector of BWYV (96% transmission efficiency) but cabbage aphid can also transmit it (14% transmission efficiency) as can cowpea aphid. Certain strains of BWYV commonly infect pulse crops in south-western Australia, New South Wales and South Australia, while other strains are limited to canola only.