Phytophthora Rot of Citrus Fruits

Citrus Phytophthora gummosis , also known as Phytophthora gummosis , is a serious disease caused by fungi of the genus Phytophthora , mainly P. nicotianae and P. citrophthora . This fungal disease can cause significant damage to trees and reduced fruit production. At Agrumiverse , we help citrus growers understand this disease and protect their orchards by providing prevention advice and quality citrus plants .

Symptoms of Citrus Rot

Symptoms of Phytophthora rot vary depending on the species of Phytophthora involved and the part of the tree affected. The most common symptoms include:

On the roots:

• Rootlet destruction: Small roots are the first to be destroyed, affecting the tree's ability to absorb water and nutrients.
• Main Root Rot: The main roots rot, further limiting water and nutrient uptake, weakening the tree.

On the trunk and branches:

• Gum exudation (gummosis): A viscous gum discharge appears on the trunk and main branches. The gum is initially transparent, but turns reddish-brown as it oxidizes.
• Brown lesions on the bark: Brown spots form on the bark, which may then crack and fall off.

On the leaves:

• Yellowing: Leaves on infected branches turn yellow and fall prematurely.

On fruits:

• Brown spots: Brown spots appear on fruits, especially around flower scars.
• Fruit rot: Fruit rots, compromising the harvest.

Citrus Species Affected by Phytophthora Rot

All citrus fruits can be affected by Phytophthora rot, but some species are more susceptible than others:

Very sensitive:

• Lemon
• Lime tree
• Grapefruits

Sensitive:

• Orange tree
• Mandarin
• Clementine

Moderately sensitive:

• Kumquat
• Calamondin
• Limequat

Variable sensitivity:

• Satsuma mandarin (depending on the variety)
• Buddha's Hand (little information available)

Prophylaxis against Phytophthora Rot

Prevention is essential to combat Phytophthora rot. Here are some recommended measures:

• Choosing a resistant rootstock: Bitter orange ( Citrus aurantium ) is often used because it has some resistance to gummosis. Other resistant rootstocks can also be considered depending on soil conditions.
• Ensure good soil drainage: Plant citrus trees on mounds or hills to prevent water from accumulating around the roots.
• Manage irrigation: Avoid overwatering and allow the soil to dry between waterings.

Treatment of Phytophthora Rot

Available sources do not provide specific details on treatments for Phytophthora rot in citrus. However, fungicides such as Aliette (fosetyl-Al) are often used to treat Phytophthora gummosis. It is important to consult a crop protection specialist for recommendations tailored to each situation.

Important Points

Phytophthora rot is a serious disease that can cause significant damage to citrus trees and affect fruit production. Strict prevention is essential, and prompt action in the event of infection is imperative to limit the spread of the disease. Consult a specialist for advice on treatments appropriate for your crops.

FAQ

What are the main symptoms of citrus Phytophthora rot?

Symptoms include root destruction, gum exudation on the trunk and branches, yellowing and premature leaf drop, and brown spots on fruit.

Which citrus fruits are most vulnerable to this disease?

The most susceptible species include lemon, lime, and grapefruit. Other species such as orange and mandarin are also susceptible.

How to prevent phytophthora rot?

Prevention includes choosing resistant rootstocks, improving soil drainage, and careful irrigation management.

What conditions favor Phytophthora rot?

Excess moisture in the soil, injuries to the trunk and branches, and warm temperatures favor this fungal disease.

Are there any effective treatments for Phytophthora rot?

Fungicides such as Aliette (fosetyl-Al) are used to treat Phytophthora infections, but it is advisable to consult a specialist for specific recommendations.

Why is it important to act quickly in case of infection?

Prompt intervention limits the spread of disease and reduces damage to trees, helping to preserve orchard health and fruit production.