Carrot virus Y (CarVY) is spread by aphids and causes mild leaf and severe root symptoms in carrots. It seriously diminishes quality if plants are infected at an early growth stage.
CarVY infects some other plants belonging to the same plant family as carrots (Apiaceae) such as anise, chervil, coriander, cumin, dill and parsnip. It does not infect celery, fennel, parsley and several other related herbs.
CarVY has only been detected in Australia. It has been found in carrot crops in New South Wales, Queensland, South Australia, Tasmania, Victoria and Western Australia. It has been detected at higher levels when carrot crops were grown throughout the year at the same site without a break in production.
Symptoms and losses
In carrot plants, leaf symptoms include chlorotic mottle (irregular small yellow patches), marginal necrosis (browning around leaf edges), and increased subdivision of leaflets giving a feathery appearance with affected plants showing mild stunting (Figure 1).
In the roots, the most severe symptoms are seen when infection occurs early – carrot seedlings infected up to six weeks after germination – and include stubby or shortened roots, knobbliness and severe distortion rendering them unmarketable (Figure 2).
Later infection – carrot plants infected more than six weeks after germination – produces milder symptoms of thinner carrots with only slight distortion, but still with a substantial overall yield loss (around 30%).
In some cases, crops have been abandoned due to large-scale early infection and the severe root symptoms that result.
All commonly grown carrot cultivars are susceptible to CarVY.