Avocado Anthracnose Disease: Prevention and Treatment

You pick your avocados looking perfectly green and healthy. A few days later, black spots appear on the skin and the flesh underneath has started to rot. This is anthracnose, one of the most widespread and damaging post-harvest diseases of avocado in India. Research from India published in 2025 confirms that Pestalotiopsis and Colletotrichum species are the primary fungi causing anthracnose-like symptoms in Indian avocado orchards. Understanding this disease can save a large portion of your harvest.

What Causes Anthracnose in Avocado

Anthracnose is caused primarily by fungi in the Colletotrichum gloeosporioides species complex. These fungi infect the fruit on the tree during the growing season but the symptoms often do not appear until after harvest when the fruit starts ripening. This is called latent infection, where the fungus is present but dormant on the fruit and only becomes active once the fruit begins to ripen. Warm temperatures around 24 degrees Celsius combined with high humidity and wet conditions during the monsoon are ideal for the fungus to spread. Spores travel through splashing water during rain and irrigation.

How to Identify Anthracnose

On the tree, early anthracnose shows as small dark spots usually less than 5 millimetres in size around the natural pores or lenticels on the fruit skin. These are easy to miss. After harvest during ripening, the lesions enlarge rapidly, turn dark brown to black, and become sunken. The infected areas may show a concentric ring pattern. In advanced cases, pink or salmon-coloured spore masses appear on the lesions. The flesh beneath the black spot is usually rotted in a hemispherical shape. On leaves and shoots, anthracnose shows as brown or black lesions and can cause dieback of young shoots.

When is the Risk Highest

In India, anthracnose risk is highest during and after the monsoon season when humidity is high and temperatures are warm. Orchards with dense canopies where air cannot circulate freely have much higher disease pressure. Fruit that has suffered any mechanical damage from insects, pruning tools, or rough handling is much more susceptible to infection. The infection window is long, from fruit set all the way to harvest, but most damage becomes visible only after picking.

Prevention: Cultural Practices First

Good orchard management is the most important defence against anthracnose. Prune your avocado trees to open up the canopy and improve air circulation. Remove lower branches to maintain at least 60 centimetres of clearance between the ground and the lowest limb. This reduces the humidity inside the canopy where spores thrive. Remove and destroy any infected fruit, leaves, and fallen debris from the orchard floor regularly. These are sources of spores that reinfect healthy fruit. Avoid overhead irrigation during flowering and fruit development as wet foliage dramatically increases infection risk.

Fungicide Management

Research published in India in 2025 tested multiple fungicides against Pestalotiopsis species causing anthracnose-like symptoms in avocados. Hexaconazole 5 percent EC and Propiconazole 25 percent EC showed the highest efficacy. Combination products including Tebuconazole plus Trifloxystrobin and Pyraclostrobin plus Epoxiconazole were also effective. Start a preventive fungicide spray program from fruit set, not after symptoms appear. Spray every 2 to 3 weeks during high humidity periods, especially through the monsoon. Alternate between different fungicide groups to prevent the development of resistance. Always follow the label instructions for dosage and safety precautions.

Post-Harvest Handling to Reduce Losses

Since anthracnose mainly shows up after harvest, careful post-harvest handling is critical. Harvest fruit with scissors or clippers, never by pulling, to avoid creating wounds where fungi can enter. Handle fruit gently to avoid bruising. Grade out any fruit showing even small spots before storage or transport as these will spread disease to healthy fruit nearby. Store at 5 to 8 degrees Celsius to slow down the ripening process and reduce the speed at which any latent infection becomes visible. Avoid storing avocados in high humidity conditions without good air movement.