Pathogenic fungi in Tasmania: Cypress Canker

Pests & Diseases

Cypress canker, caused by the fungal pathogen Seiridium, is a significant problem affecting a wide range of Cypress species worldwide.

This disease can cause significant damage to residential tree plantings, particularly windbreaks and hedges.

Seiridium is a ubiquitous pathogen, and it is often present in asymptomatic trees. It becomes a problem when the tree becomes stressed, and the fungus takes advantage of this weakened state to invade the tree’s tissues. The fungus primarily infects damaged parts of the tree, such as pruning wounds, limb shear, or cracks in the bark, which can serve as entry points for the spores.

The first signs of Seiridium canker are resin or sap flow on the trunk or branches. As the disease progresses, the foliage will begin to die back, starting from the branch tips and moving inward. Eventually, the entire tree may succumb to the disease, which can be fatal.

Seiridium canker can be exacerbated by other factors, such as drought and excessive rainfall, which can cause additional stress on the tree. Trees that are regularly fertilized with high levels of nitrogen may also be more susceptible to the disease. In addition, high-density plantings can increase the risk of infection, as trees may become more prone to damage from wind and other environmental stresses.

In this article we will investigate:

  • Host Species impacted by Seiridium canker
  • How do I manage Seiridium canker?
  • What do I do if I detect Seiridium canker?

Cypress Canker

Figure 1. Evidence of cypress canker disease on a twig of Thuja plicata.

Cypress Canker

Figure 2. Cracked bark in infected areas is often accompanied by resin that flows down.

Host Species

There are a few species of Cypress that are considered less susceptible to Seiridium canker, including Arizona Cypress (Cupressus arizonica), Bhutan Cypress (Cupressus torulosa), Western Red Cedar (Thuja plicata), Thuja occidentalis, and Juniperus virginiana. These species may be a better choice for residential plantings, particularly in areas where Seiridium canker is a known problem.

How do I manage Seiridium canker?

Prevention is the best way to manage Seiridium canker. Proper tree care practices can help reduce the risk of infection and keep the trees healthy. This includes regular pruning to remove damaged or diseased branches, as well as thinning the tree canopy to improve air circulation. Trees should also be watered properly to avoid both drought and waterlogged conditions. Avoid using high levels of nitrogen fertilizer, which can promote rapid growth and make the tree more susceptible to infection. Finally, it is essential to avoid planting Cypress trees too close together, as this can increase the risk of damage and stress.

Cypress Canker

Figure 3. Dieback as a result of Seiridium canker

What do I do if I detect Seiridium canker?

If Seiridium canker is suspected, it is important to take action quickly. Early detection and treatment can help prevent the spread of the disease and limit its impact on the affected trees. Fungicides are available that can help control Seiridium canker, but they are most effective when applied preventively, before the disease has a chance to take hold. Fungicides can be applied as a spray or injected directly into the tree’s trunk, depending on the severity of the infection.

In severe cases, it may be necessary to remove the affected tree entirely to prevent the disease from spreading to nearby trees. All infected plant material should be carefully removed and destroyed to prevent the fungus from spreading further.

Seiridium canker is a significant problem affecting Cypress trees worldwide, including those in residential plantings. However, proper tree care practices, including regular pruning, thinning, and watering, can help reduce the risk of infection and keep the trees healthy. Additionally, choosing less susceptible species and avoiding high-density plantings can help minimize the risk of Seiridium canker. Early detection and treatment are critical in preventing the spread of the disease, and infected trees should be removed and destroyed to prevent the fungus from spreading further. By taking these steps, homeowners can help protect their Cypress trees and keep them healthy for years to come.

Images courtesy of Department of Primary Industries and Regional Development, Golden Urban Forest, and Wikimedia Commons.


Tasmanian Tree Care and it’s highly trained arborists can identify potentially harmful fungi in your garden or property. If you’re unsure about the health of your natural assets, please contact us to organise an assessment.

Content collected by Colin Fry

Colin Fry has spent the past two decades as a devoted arborist in Tasmania, and has been director of Tasmanian Tree Care since its inception in 2014. He is passionate about leading a purpose-led organisation that is a vessel for change, and investing in the personal and professional growth of his employees through arboriculture. 

Click here to learn more about our team.

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Cypress canker FACT SHEET

Want to learn more about Cypress canker? Check out our detailed Fact Sheet below.

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