Sooty blotch
- The fungus overwinters on twigs of various woody plants in hedgerows and windbreaks and on apple twigs.
- In spring, pycnidia (fruiting bodies) on wild plants and apple twigs produce large numbers of spores (conidia) that ooze out and are spread by rain splash or wind blown mist in orchards in spring and early summer to autumn.
- The fungus first infects apple twigs and from these infections fruit are colonised from late June/early July onwards.
- Cool, humid weather (optimum 18oC) is essential for disease development.
- Free water on the fruit surface is required for infection.
- The disease does not develop at high temperatures or if conditions are dry in late summer.
- The incubation time from fruit infection to symptom appearance can be as short as 5 days under optimum conditions.
- In the orchard the incubation period usually lasts 3-4 weeks on fruits that are 42-45 days old.
- The blotch symptom on the fruit consists of hundreds of minute pycnidia interconnected by fungal mycelium.
- The fungus can also continue to develop in store.
Fly speck
- Fly speck similarly overwinters on wild hosts and on apple twigs as sexual fruiting bodies (pseudothecia).
- In spring these release ascospores around blossom time which infect apple twigs.
- Conidia produced on these infections spread to infect apple fruits.
- Optimum temperature for conidial production is around 17oC at high humidity.
- Conidia are spread by wind to infect fruit.
- Free water on the fruit surface is required for the fungus to infect.
- In the orchard there is usually three weeks between fruit infection and symptom appearance on apple fruits.
- On the fruit the individual fly specks are the fungal fruiting bodies.