DISEASE
 
   NAME
     Apple Scab, Black Spot
     Venturia inaequalis

Description
Pathogenic, Fungal

Symptoms
This fungus attacks fruit and leaves by forming small pale green spots 3mm across that merge forming large patches that become black. The spots become leathery where spores develop and the leaves curl while the fruit develops cracks. Although the fruit is marked it normally is still editable.  

Image by Ohio State University 

Source and Dispersal
The fungus overwinters on infected leaves even after they have fallen and the spores are dispersed by splashing water. During spring spores are released and dispersed by wind infecting new leaves and fruit. It is also spread by infected plant material.

Favoured Conditions
Infection occurs when a dry cool period is followed by wet period that is longer than ten hours and remaining humid. 
 
Affected Plants
Many species of apple are affected including ‘Granny Smith’ and ‘Delicious’. it is also found on the ornamental Malus species.
A simular fungus Scab (Fusicladium pirinum var. pyracanthae) infects Pyracantha species.

Non-chemical Control
There is no effective non-chemical control, but clearing fallen foliage from under the plant and removing infected material from the tree helps to control. All infected material should be burnt.

Chemical Control
Preventative spraying of fungicides is required. Bordeaux, copper oxychloride or zineb should be used before the next crop when the conditions are conducive for infection
Note
Always read the label for registration details and direction of use prior to application of any chemicals.