To solve a soursop situation

Dear Rayanna,

My name is Amrad and I am an avid reader of your articles. I need some help for my soursop tree. Up to about 18 months ago the tree (which is about four years old and approximately 15 feet tall), would bear some beautiful fruit. They would weigh about 10 pounds without spot or blemish.

However, the tree suddenly stopped bearing so I mulched and fertilised. It started bearing again a few months ago and I got three nice fruits. 

Now the tree is flowering, and the fruits get about as large as an orange and then fall off. The fallen fruits have a hard, dry, black spot on them that cover a quarter to a little more than half of the fruit in some instances. In the past few weeks I have thrown away about 30 fallen soursops. I am considering cutting off the top half of the tree to see if that would make a difference.

 Your assistance and advice would be greatly appreciated. — Amrad

Hi Amrad,

Thank you for your interest in the column. I’m very sorry to hear about your soursop tree.

There are three main pests that attack soursop:

Root grubs—Root grubs are insects that feed on the roots of trees. They usually prefer trees with fibrous root systems. They prefer to stay in locations where there is moisture. These pests can cause problems like discoloration of the plant, wilting and abnormal plant height

Mealy bugs—These are tiny insects with soft bodies. The mealy bugs that are visible are the females and these types of insects suck the juice out of the plants. These pests prefer to target young trees and can lead to discoloration of leaves. After a period, the leaves fall off. These pests can also cause the fruits and vegetables to fall off early. Their excretions can lead to growth of fungus

Carpenter moths—A carpenter moth looks like a butterfly and attacks trees which have hard wood and a strong odour. These pests can build large tunnels in the wood. The larvae spend some time in the tree and develop into pupa months later. Infected trees are at a risk of breaking. These pests can also affect the appearance of the tree and make it look deformed.

Then there are diseases such as:

Root rot— as the name suggests, it is a condition where the roots of the plant decay. It is a common problem and your tree is beyond saving once it contracts this disease. Root rot usually occurs when the roots of the tree are not able to get enough water. As a result, the soil becomes dry and the roots are not able to get the essential nutrients that they need to survive and grow

Anthracnose—Fungi called Colletotrichum are responsible for causing this disease in trees. It causes the plants to develop wet lesions on the leaves

The problem that you are describing sounds like it has the fungal infection of Anthracnose.

Here is what you can do:

Prune the dead branches and destroy the infected leaves (burn them).

You can try spraying your plants with a copper-based fungicide, though be careful because copper can build up to toxic levels in the soil for earthworms and microbes.

Ensure you use full personal protective equipment (PPE) when spraying. Continue to fertilise the tree and stick to the spray regime as directed on the fungicide.

To prevent Anthracnose, plant in well-drained soil. You can also enrich the soil with compost in order to help plants resist diseases. Keep ripening fruits from touching the soil.

Let me know when the tree makes progress!

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