Plantwise Factsheets for Farmers

Anthracnose disease is caused by a fungus. Many farmers lose money when their avocado fruits get anthracnose disease, and the fruits cannot be sold. This disease is common among many other fruits including mangoes and pawpaw.
Round, black spots form on the fruits and leaves. The spots have a sunken, rotting grey centre, where the fungus is growing. Fruit fly damage may look similar, but spots caused by fruit flies do not have the grey area.

The disease is more common in the rainy season or in wet conditions. Very shady fields can be too wet. The disease is caused by a fungus which is spread by small seeds called spores. Wind and water carry the spores from sick plants to healthy ones. Plants can get anthracnose at any stage, but it causes the most damage between flowering and harvesting.

• Provide adequate drainage in flat areas. Plant on cambered beds.

• Keep the field dry by planting avocadoes 6 metres (20 feet) by 6 metres (20 feet). Plant further apart in wetter areas.

• Prune trees at the start of the dry season, to reduce shading and the amount of diseased material on the tree and in the fields.

• Remove diseased leaves and fruits from the field.

• If the fruit is diseased, there is no cure. Chemical control can help to manage the disease.

• Spray fungicides when the trees start to flower and continue every two to three weeks up to one week before harvesting. Copper-based fungicides may be used in rotation with other fungicides such as dimethomorph and mancozeb. Rotating chemicals is important to prevent the fungus from getting used to the chemical. If this happens, the chemical will no longer work.

• Follow recommended application rates from the label of the fungicide.

• Spray chemicals with a mist blower which spreads the chemical evenly on fruits and leaves. If you use a spray can, the chemical will NOT reach leaves at the top of the trees. Mix a spreader-sticker with the fungicides to help keep the chemical on the plants, especially during the rainy season.

When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.