Brown Rot (Monilinia fruitigena)

Plants/trees affected

Stone Fruit Trees such as Apples, Pears, Plums

Symptoms

Small soft brown circles or spots appear on mature fruit which spreads and eventually envelops the whole of the fruit.  It then shrivels followed by pale grey/buff coloured pustules on the surface and these are the fungus spores. What is left of the fruit will either remain mummified on the tree or fall.  Fungus spores on infected fruit can also infect and rot stems, leaves and flowers on the tree. Damaged fruit may affect the whole harvest if stored in close contact with the rest of the crop.

Causes

This disease is caused by a fungus, which survives the winter on the mummified fruits either on or off the tree and in cankers formed on infected spurs/twigs. Thousands of spores are spread by air movement and even a small amount of rain will allow them to germinate and affect new blossoms or young shoots.  Young fruits are not normally susceptible unless damaged in some way but as the fruit matures it is prone to attack from insects who will wound the fruit and spread the fungus.

Prevention

Sanitation is all important, any rotten fruit either on or off the tree should be removed and destroyed.  Affected stems/spurs should be pruned back in winter and the control of insects which attack the fruit is vital.  Careful harvesting and storage of the crop is also necessary to avoid bruising or damaging the fruit which would then make it vulnerable to infection. 

Treatment

• Remove and destroy as soon as possible any infected flowers, leaves, stems and fruit.  
• No chemical control is available to prevent brown rot but it is possible to control the pests which attack the fruit hence reducing the incidence of brown rot.

• Regularly check stored crops and remove any fruit showing signs of brown rot.