Leyland Cypress Needle Blight – Causes & Treatment

As with most tree species, diseases cause a substantial amount of damage to either the roots, stem, or leaves of the tree.

Fortunately, some of these diseases are preventable by taking the correct precautions. Evergreen trees, like the Leyland cypress and blue spruce, shed off old needles and grow new ones. This helps reduce transpiration and increase water circulation in the tree’s structure.

The routine shedding off is known as dieback. The Leyland cypress needles will turn brown starting from the inside and work their way outwards. However, the continuous shedding off should not be confused with the needle blight disease as much as this process looks identical.

So, in this article, we will address the needle blight causes and treatment.

How Do We Treat The Disease?

The Leyland cypress tree species is a resistant and tolerant tree that grows fast and wide. It tends to be vulnerable to specific diseases if left unattended, but at the same time, it is a drought-resistant tree species. Various diseases and pest issues have become more noticeable as a result of the increased planting that has come about as a result of its popularity. However, there is one common disease known as the Leyland cypress needle blight, which attacks this tree species.

We will discuss the causes of Leyland cypress diseases, and all the practical ways you can hire to treat it effectively. But, before we continue, let us read an insight into understanding what kind of this disease is.

What Is The Leyland Cypress Needle Blight Disease?

Needle blight is a disease caused by a fungus known as Passalora sequoia. This fungus usually attacks young Leyland cypress trees that are a year or a few years young. But, today, this fungus has evolved to attack even mature Leyland cypress trees.

At first, the Leyland cypress leaves will assume a light-brownish look. But after a few weeks/months, these leaves will drop if the disease persists. The symptoms can be easily visible during summer when the weather is warm.

Studies and research have revealed that the Leyland blight disease causes the leaves of the Leyland cypress tree to change their color gradually. For instance, in spring (about mid-May to mid-June), the Leyland cypress leaves begin to turn reddish-brown, and between August-September (summer), the leaves turn light brown and dark brown.

In the final stages, the needles turn yellow and drop immensely.

Note that this disease affects a tree throughout its growing seasons, and if it is not treated quickly, it can cause severe damage or even tree death.


An infectious fungal pathogen causes Leyland blight disease known as Passalora sequoias. This pathogen was earlier known as the “Cercospordium, Cercospora, and Asperisporium.” This fungus causes progressive damage to the leaf tissues of the tree. When there is excess moisture in the air, the Leyland cypress tree and other conifer trees will be likely affected by the needle blight disease. Also, if the Leyland cypress trees are planted close to each other, there is a high risk of disease transmission.

Inadequate air circulation is another leading cause of needle blight disease.

Early Signs And Symptoms

Before needle blight treatment, you need to know the early signs and symptoms that can be physically noticeable. Knowing these signs will help you understand how to address this issue and deal with the situation effectively.

Some of the early signs and symptoms of needle blight include;

  • Discoloration of the lower branches
  • Foliage loss
  • Needle defoliation

Prevention And Treatment

To treat needle blight disease, you need to understand how it behaves and a few applicable prevention methods.


Plant trees with adequate spacing to allow for proper airflow. To prevent the disease, you need to plant trees about 3.5 meters (12 feet-15 feet) apart. This allows sufficient air to flow through even as the trees mature. If you are planning to water young Leyland cypress trees, you should avoid the overhead kind of irrigation. Or limit it to early in the morning to reduce spore spread.

Why is this so? Overhead watering is a resourceful and inexpensive irrigation method.

But, with overhead irrigation, most of the water will miss some areas and hit other areas. Instead, use the drip style of irrigation when there is a drought. Drip irrigation ensures that enough water sips down the roots of each plant equally.

Hoses should be no longer than 75 feet in length, as pressure drops dramatically beyond that point. Remove diseased limbs with pruning shears, wiping down tools with a solution of 10% bleach between cuts (1 part chlorine bleach to 9 parts water).

After this process, remember to clean and oil your pruning tools to avoid rust. Additionally, pruning all the diseased/affected leaves can help prevent the disease from spreading to the other parts of the tree. However, you need to know the exact season to prune.

The best time to prune/trim trees are during the mid-late winter months. This is between November through March.

In winter, the trees are dormant and less susceptible to both insects and diseases. However, if the Leyland cypress tree is diseased, you need to prune it immediately without hesitation.

Check this: Best 6 Electric Pruning Shears

If you have identified the fungal infection during its early stages, you can prevent it from spreading to the other parts of the tree by trimming the affected lower branches.


Many homeowners and cultivators treat diseases using the wrong prescriptions. The wrong prescription and misleading diagnosis can cause significant damage to the trees. Therefore, it is essential to treat tree diseases using the correct medicines from the arborist.

There is one common way of treating the Leyland cypress needle blight:

Use Of Recommended Water-based Fungicides

Water-based fungicides are chemical compositions that are manufactured and approved for killing fungus pathogens. The Liquid Copper Fungicide Spray is a vital chemical solution in disease treatment and prevention on a large variety of trees.

When treating the needle blight fungal infection using a fungicide, it must be carefully and correctly applied. It takes between three to eight days for a fungicide to be effective after application.

Using the correct fungicides has a positive effect on the life of the tree. You should spray the infected Leyland cypress trees with specific fungicides at regular intervals to reduce the needle blight disease.

Below, we will show you the correct amount of fungicides to use and the exact time intervals to apply them.

There are two stages involved during this process.

  • Early treatment
  • Late treatment

During the early treatment stage, the amount of fungicide concentration used should be monitored keenly. The right amount applied during the early stages/first signs of this disease should not be more than 100mm of dosage. After a few days, you need to re-apply the fungicide to boost its effectiveness. Monitor the tree for signs of disease cure. If the needle blight persists even after routine application, you will need to consult with a local tree expert.

During the late treatment stage, the amount of fungicide applied should not be in excess. This is because the tree’s structure tends to be weaker at the later stage of illness. However, when dealing with severely damaged trees, you need not re-apply the fungicide at close intervals. Again, monitor the tree for signs of disease cure.

If the needle blight persists after routine application, you should consult with your local tree experts.

Step By Step Procedure To Needle Blight Fungicide Application

Before applying the recommended fungicide, you need to know the exact steps to follow.

Below is a guide:

  • Ensure to wear all the personal protective gear
  • Measure the amount of fungicide with water, using the instruction guide available on the bottle’s label
  • Using a hand pump/horse pipe, spray the fungicide according to the instructions provided on the bottle’s label
  • Apply fungicide evenly on the surface of the tree and on the ground to ensure the disease does not spread
  • Allow the product to dry completely before reapplication (often 3-4 days).

When Should You Use Fungicides?

It is best to use fungicides before it rains. When dealing with needle blight disease, you should apply the correct fungicide a few days (up to a week) before the rains. But for these sprays to work, they must start in the late spring and continue all the way through the summer until the fall’s cooler and less humid months. This allows the tree to absorb the chemical sufficiently.

Don’t: You should not apply the fungicide as it rains. Rainwater washes away the chemical composition; hence the fungicide will not be effective. To effectively spray/inject your Leyland cypress tree with the recommended fungicide, we advise reading a guide or conducting online research.

This will help you understand all the crucial details like; the amount of dosage and specific dates to carry out the process. Additionally, it’s critical that needles, including those inside close to the trunk, are thoroughly sprayed to run off when applying these fungicides. A homeowner cannot generally provide adequate coverage once a tree reaches a certain height.

If you are not sure of the process, contact the local tree expert and let them advise accordingly.

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Six Rules For Needle Blight Fungicide Application

  • Use recommended fungicides before the development of the needle blight disease
  • Apply fungicide in shorter spray intervals when the weather is conducive to plant disease
  • Apply the fungicide before the rainy season
  • Alternate between different fungicides to deal with mutated fungi
  • Double-check the label for details
  • Before applying the fungicide, you should adhere to the Post-Harvest Intervals


To treat needle blight disease, you need to understand its behavior and effects fully. The above insight has outlined the practices and a step-by-step guide to applying the recommended amount of fungicide dosage.

Deal with the disease in its early stages and prevent it from killing the tree eventually.

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