Apple canker is an economically important disease of apple and is one of the most important diseases in the UK and recognised as a serious problem as early as 1710.
- The fungus attacks twigs and branches, causing cankers and dieback in mature trees, and often death of young trees.
- It also attacks fruit causing rots both in the orchard and in store.
- Losses due to canker are difficult to estimate, but those of 10% or more in young trees in newly planted orchards are typical and, in seasons favourable to the disease, losses due to rots in stored fruit can be as high as 30%.
- The fungus is not specific to apple and attacks pear and quince and several forest and hedgerow trees including beech (Fagus), poplar (Populus), hawthorn (Crataegus) and Acer.
- N ditissima on ash (Fraxinus) is thought to be a separate strain formae speciale
- Alder (Alnus) is susceptible to artificial inoculation but no natural infections have so far been observed.
- These other susceptible species could therefore act as a source of Neonectria inoculum. In practice only poplar has been implicated in canker outbreaks in apple orchards.
- The disease is present in virtually all the apple producing areas of the world except Australia.
- Its prevalence as canker or fruit rot is dependent on seasonal rainfall patterns.