Citrus Melanose: A Guide for Young Farmers
What is Citrus Melanose?
Citrus melanose is a disease that affects all types of citrus trees, including oranges, grapefruits, and lemons. It causes damage to the leaves and fruit rinds, making the fruit look unattractive. Although the pulp of the fruit is usually not affected, the disease can weaken the tree and reduce fruit production.
What Causes Citrus Melanose?
Citrus melanose is caused by a fungus called Phomopsis citri. This fungus grows on dead twigs and branches of citrus trees. When it rains, the spores of the fungus are spread by water droplets to other parts of the tree and to other trees. Grapefruit and lemon trees are most susceptible to citrus melanose.
Symptoms of Citrus Melanose
The symptoms of citrus melanose are most visible on the leaves and fruit.
- Leaves: Small red-to-brown spots appear on the leaves. These spots are often surrounded by a yellow ring, but this coloring fades as the disease progresses. The surface of the leaf becomes rough and bumpy.
- Fruit: Brown spots or pustules develop on the fruit. These spots grow together and crack, creating a condition known as “mudcake.” The spots may also spread down the fruit with dripping water, forming “tear stains.”
Preventing Citrus Melanose
There are several steps you can take to reduce the risk of citrus melanose in your garden:
- Trim dead branches and twigs: The fungus that causes citrus melanose grows on dead wood. By removing dead branches and twigs, you can help to prevent the spread of the disease.
- Disinfect pruning shears: Before using pruning shears on healthy branches, disinfect them with a bleach solution. This will help to prevent the spread of the fungus from infected branches to healthy ones.
- Avoid overhead watering: Overhead watering can spread the spores of the citrus melanose fungus. Instead, water your citrus trees at the base of the trunk.
Treating Citrus Melanose
If citrus melanose develops in your trees, you can use fungicides to control it. Copper fungicides are the most commonly used type. You can get recommendations and instructions for use from your local nursery or agricultural extension office.
When to Use Fungicides
Fungicide treatment is not always necessary for citrus melanose. The disease does not make the fruit inedible, and in most cases, it does not cause serious damage to the tree. However, if the infection is severe, it can weaken the tree and reduce fruit production. Fungicides can be used as a last resort if prevention and control methods don’t keep the disease under control.
Additional Tips
- Inspect your citrus trees regularly for signs of citrus melanose.
- Remove any infected leaves or fruit from the tree and dispose of them in the trash.
- Keep your citrus trees healthy and vigorous by providing them with proper care, including regular watering, fertilization, and pruning.
