Phytophthora Root Rot Disease Explained

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Phytophthora, or root rot, is one of the most common plant diseases. It is hazardous because it infects different species, can pass from one plant to another, is very harmful, and adapts well to new climatic conditions.

Phytophthora is a fungal disease. Its causative agents are fungi of the genus Phytophthora, which are spread by zoospores. Spores are washed by rains into the soil, infecting underground and aboveground parts of other plants through mechanical damage and wounds caused by pests.

Phytophthora leads to dry bark and desiccation of the tree, and if the disease is neglected, the plant is likely to die.

The main problem in controlling root rot is that it can be diagnosed in the late stages when it is already difficult to cure a particular plant. Therefore, the main task is to prevent the spread of the disease.

Symptoms of Phytophthora

There are several symptoms of root rot:

  • The plant wilts even with sufficient watering.
  • Roots are rotten.
  • Dry spots on the leaves.
  • Red-brown color of the bark.


Phytophthora fungi that cause root rot can survive in the soil for many years as long as wet conditions persist. The disease can spread through rain splashes, irrigation water, and sewage.

There are also three primary forms of the disease:

  • Internal bark necrosis of woody crops or “sudden death.”
  • The death of shoots or branches.
  • The so-called “leaf scorch” results from an infestation of the foliage.


In addition to the above, universal signs of phytophthora are brownish-gray spots often surrounded by a ring of white mold or covered with a spiderweb-like plaque. Affected plant parts die off quickly, but leaves remain hanging from the branches even after the tree dies. 

Combating Phytophthora

It is tough to stop the development of this disease. The main preventive control measures include planting trees and plants in uninfected areas.

In addition, the following tips will be helpful:

  1. Carefully inspect the soil before planting to ensure drainage does not reach the roots of trees. Do not allow water to stagnate around the root system.
  2. Try to plant trees in an elevated location so that puddles of standing water do not form around the plants. Never plant trees deeper than you grew them in the nursery.
  3. Separate plants, shrubs, and trees according to their watering needs and avoid overwatering.
  4. Remove excess soil. If the dirt has accumulated over the roots, carefully remove it to expose the root neck. It is where fungal infections most often occur.
  5. Choose a plant resistant or less susceptible to root rot.



Phytophthora treatment is most often done with a variety of natural or chemical fungicides.

Biological Fungicides 

The most natural way of root rot control is Trichoderma – a special fungus that feeds on other fungi. It grows around the tree’s root and feeds on all pathogens in the ground, including Phytophthora. That way it stops it from invading the root and killing the tree.  

Other effective, completely natural ways of curing Phytophthora are biological preparations. They are a more modern and environmentally friendly method of fighting because they contain live microorganisms that feed on fungal spores. And while chemical plant protection agents suppress almost all simple soil fungi, among which there are useful ones, biological preparations do not allow pathogenic fungi to spread.

Chemical Control

The most effective chemical way of controlling Phytophthora is Phosphonate fungicide. If the tree is still not infected, it increases the tree’s tolerance and resistance to the disease. If the tree is infected, phosphonate will help to stop mold development. 

Phosphonate fungicide is applied in two ways: directly into the trunk or sprayed onto the bark. 

Tree injection is a complex procedure that requires experience. If you inject chemicals into the wrong part of the tree, the cure might not be as effective, because the tree’s vascular system will take it to the fastest-growing part of the tree.

injection, tree, bark, trunk, hand in gloves, fighting root rot

Spraying phosphonates onto the bark and the ground around the tree is a simple yet effective way of controlling the disease. The tree absorbs it through the bark and transports it to the infected parts. 

In both ways, the tree’s vascular system delivers the chemical into the roots and other infected parts of the tree, but only if carefully injected or sprayed. 

If you notice even one of the signs of phytophthora on your plants, contact us immediately. Our experts will examine your plants, determine the type of disease and extent of damage, and offer the best treatment.

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