Black spot

Black spot symptom on strawberry

Cause

The fungus Colletotrichum acutatum.

Symptoms

• Circular, dark brown, sunken spot in the fruit
• Fruit remains firm
• White fungal growth, followed by orange spore masses, develops on the spots
• Pathogen may also cause necrotic lesions on the leaf

How it spreads

The fungus infects leaves and green fruit. After penetration it can remain dormant in the tissues.

Black spot may develop in fruit when they begin to ripen and in leaves when conditions favour disease development.

The main source of infection is spore masses produced on old, undecomposed leaves and shrivelled fruit. The spores are spread by rain splash, by overhead irrigation and on the hands of pickers. The fungus may also be introduced in diseased runners.

Fruit that show no symptoms at harvest may still develop black spot during transit or storage.

Crops affected

The genus Colletorichum sp. can cause anthracnose disease on many fruit crops such as:

• avocado
• banana
• citrus
• custard
• apple
• lychee
• macadamia
• mango
• passionfruit
• persimmon.

Control

• Handle fruit carefully during and after harvest to minimise injury
• Store fruit at the optimum temperature after harvesting and during transport
• Plant certified runners
• If possible, avoid overhead irrigation, which favours black spot development
• Remove sources of inoculum, such as dead leaves and diseased fruit
• Use a recommended fungicide program

Chemical registrations and permits

Check the Australian Pesticides and Veterinary Medicines Authority database for chemicals registered or approved under permit to treat this pest on the target crop in your location. Always read the label and observe withholding periods.