Greasy Spot on Citrus Fruits: Symptoms, Prevention and Control

Greasy Spot is a fungal disease affecting citrus trees, caused by the fungus Mycosphaerella citri (also known as Zasmidium citri ). This disease is common in tropical and subtropical regions and can have detrimental effects on fruit growth, quality and quantity. At Agrumiverse , your citrus plant supplier and citrus plant wholesaler , we help you prevent and manage this disease to protect your orchards.

Greasy Spot Symptoms

Greasy Spot symptoms primarily affect citrus leaves, but can also appear on the fruits of certain species, such as grapefruit. Here are some signs to look for:

On the leaves:

• Underside of mature leaves: Appearance of yellow lesions evolving towards a dark brown or black color, slightly raised.
• Upper surface of leaves: Diffuse yellow spots corresponding to lesions on the underside of the leaves.
• Premature leaf drop: In cases of severe infection, leaves may drop prematurely, weakening the tree.

On fruits (mainly grapefruits):

• Small necrotic spots: Small brown spots appear on the skin of the fruit.

It is important to note that Greasy Spot symptoms can sometimes be confused with damage caused by certain mites, requiring careful monitoring for a correct diagnosis.

Citrus Species Affected by Greasy Spot

Greasy Spot can affect all citrus species, but some are more susceptible than others:

Most sensitive species:

• Grapefruit: One of the species most susceptible to this disease.
• Lemon and Lime: These two species are particularly vulnerable to Greasy Spot.

Moderately sensitive species:

• Orange tree: Although less susceptible than grapefruit and lemon trees, orange trees can be affected.
• Mandarin and Clementine: These species have moderate sensitivity.

Less sensitive species or little information:

• Calamondin, Kumquat, Limequat, Buddha's Hand: Although these species are not specifically mentioned as being susceptible to Greasy Spot, they can potentially be affected.

Citrus susceptibility can vary depending on environmental conditions and cultural practices. Regular monitoring of trees is essential to detect early signs of the disease.

Greasy Spot Prophylaxis

Prevention is the key to limiting the development of Greasy Spot. Here are some prophylactic measures recommended by Agrumiverse , your specialist partner in citrus growing :

• Planting Density: Ensure trees are planted at an appropriate density to avoid overcrowding, which promotes stagnant moisture.
• Row Orientation: Orient tree rows east to west to maximize sun exposure.
• Drainage: Good drainage is essential after rains or irrigation to avoid excessive moisture which encourages the development of the fungus.
• Pruning: Regularly prune diseased branches before the rainy season or before the new harvest to improve ventilation in the orchard.
• Balanced Fertilization: Apply appropriate fertilization, avoiding excess nitrogen which can make trees more susceptible to infections.

Ways to Fight Greasy Spots

To combat Greasy Spot, different methods can be adopted:

Chemical treatments:

• Petroleum oil or oil-copper mixture: Apply this treatment in mid-May or June to prevent the onset of the disease.
• Copper: For more sensitive varieties, such as grapefruit, the use of copper is recommended.

Biological treatments:

• Organic preparations: Use organic treatments specific to diseases of citrus and fruit trees.
• Chitosan: Apply chitosan powder or liquid, which stimulates the plants' natural defenses.

Crop management:

• Removal of infected leaves: Remove and destroy infected leaves that have fallen to the ground to reduce inoculum in the orchard.
• Orchard Ventilation: Maintain good air circulation to reduce humidity and the spread of fungal spores.

Regular monitoring:

• Frequent orchard inspection: Early detection of symptoms is crucial to limit disease progression and avoid significant production losses.

Important Points to Remember

• Impact of Greasy Spot: This disease can significantly reduce the quality and quantity of citrus fruit, affecting the profitability of your orchards.
• Essential prevention: The implementation of appropriate prophylactic measures is necessary to limit the development of the disease.
• Integrated approach: Effective management of Greasy Spot relies on an integrated approach combining prevention, chemical and biological treatments, as well as regular monitoring of orchards.

FAQ

What are the main symptoms of citrus greasy spot?

Symptoms include yellow spots on the underside of leaves, which turn dark brown or black, and premature leaf drop. Fruits, especially grapefruit, may have small brown necrotic spots.

Which citrus species are most susceptible to Greasy Spot?

Grapefruit , lemon , and lime trees are most susceptible, but other citrus fruits, such as orange and mandarin trees , can also be affected.

How to prevent Greasy Spot in a citrus orchard?

Prevention involves planting with appropriate density, good drainage, regular pruning of trees to improve ventilation, as well as the application of prophylactic treatments such as oil-copper mixtures.

Are there any biological treatments for Greasy Spot?

Yes, organic treatments such as applying chitosan or other organic preparations can help control the disease while strengthening the citrus fruit's natural defenses.

Why is it important to monitor orchards for Greasy Spot?

Early detection of symptoms allows for rapid action to limit the spread of the disease and avoid significant losses in terms of fruit production.

How can Agrumiverse help you prevent and control Greasy Spot?

Agrumiverse , as a supplier for professional citrus growers , offers quality, disease-resistant citrus plants and provides personalized technical advice for optimal orchard management and the prevention of diseases such as Greasy Spot.