Little cherry disease is a complex and serious viral disease of ornamental and sweet cherry varieties worldwide. Little cherry disease symptoms can be caused by two different viruses: Little cherry virus-1 and Little cherry virus-2. In Australia, Little cherry virus-2 (LChV2) was detected in commercial cherry trees in Tasmania and Victoria in early 2014. Tracing indicates that potentially infected planting material has been dispersed widely throughout all Australian states (except the Northern Territory). Thereby, LChV2 is now considered endemic within Australia.
Little cherry disease symptoms vary between sweet cherry varieties and can be influenced by rootstocks and climate. Fruit develop normally until about 10 days prior to harvest when the maturation process slows dramatically. Fruit size, colour, shape, texture and flavour can all be affected, depending upon the variety infected. Fruit fail to ripen fully, and often retain a characteristic 'fire engine red' colour. Many European and New Zealand varieties show only mild fruit symptoms, and appear to be tolerant. Fruit symptoms are more severe on varieties grown on "Mazzard" rootstocks.
Leaf symptoms can also be present. This can include premature leaf reddening, where areas of the upper surface turn a red-violet or bronze colour. Mid-rib and main vein areas of the leaves typically retain their green colour for a certain period of time.Sour cherries can also exhibit some fruit symptoms.
|What do you do if you find symptoms||Report any possible infections immediately to Biosecurity Queensland on 13 25 53.|
|Susceptible plans (hosts)|
Sweet cherry, sour cherry varieties and potentially plum plants.
|Infection and spread|
Little cherry virus-2 is transmitted by the successful union of vascular tissues. For example, Little cherry virus-2 is readily bud and graft transmissible, and can be spread when tree roots grow together (root grafting).
Little cherry virus-2 can also be transmitted by the apple (Phenacoccus aceris) and grape (Pseudococcus maritimus) mealybugs. Fortunately, neither of these insects is currently present in Australia.Long distance spread of Little cherry virus-2 usually occurs through movement of infected planting material (young trees), rootstocks, scions and budwood. Short distance spread (i.e. within an orchard) occurs via insect vectors.
|Where angular leaf spot occurs|
Symptoms usually become apparent at the end of summer or in early autumn (February - March in Australia). Although in areas with cooler overnight conditions, leaf symptoms can occur mid-summer (January).
The economic impact of Little cherry virus-2 varies with the severity of symptoms caused in infected plants. Infection of very sensitive varieties can result in the loss of the entire crop, while other more tolerant varieties have reductions in fruit size, colour and flavour. However, any Little cherry virus-2 symptoms are usually sufficient to make fruit unsaleable for fresh consumption, for which most Queensland sweet cherries are grown.
Little Cherry Virus does not affect human health.
|Management and quarantine|
Plants cannot be cured of virus infections, so the only method of control is to remove infected plants, and limit vectors. The disease may be managed by growing less sensitive or tolerant varieties if available.