Why are my cypress pine trees dying?

I have many customers asking this question about their cypress pine trees. This includes all species from leighton greens (cuprocyparis leylandii) through to your generic cuppressus species. The canker can have dire affects as it not only affects Central Coast trees, but it also affects the benefits these trees provide. Removal of a beautiful tree hedge can mean the removal of your much loved privacy or the loss of a screen from an ugly building or an undesirable neighbour!

This dieback is a result of Cypress Canker.

Cypress canker is caused by several species of fungi (Seiridium cardinale, S. unicorne and S. cupressi) whose spores enter the trees through natural fissures in the bark or through injuries caused by gardening equipment or falling branches. The fungus interferes with the sap-conducting system, eventually causing death of the branch or main trunk above the wound. Older trees are usually more susceptible but any tree is susceptible if stressed, for example, by drought or poor nutrient status.

Branches die rapidly, yellowing almost overnight as the foliage is starved of sap. If untreated, the disease will eventually lead to death of the whole tree. Sunken cankers, with a reddish tinge, form at the entry point of the fungus, and resin often exudes from the edges of the cankers or through cracks in the bark. Individual cankers are long and thin and may be numerous along a branch. Spore-producing structures of the fungus can be seen on the bark surface as small, circular, black dots.

Spores are carried on the wind, in water droplets or by insects and birds. New infections develop when spores are washed down the tree or splashed from tree to tree by rain or overhead irrigation. They can also be transferred from tree to tree on pruning tools, or through the transport of infected cuttings or plants.

Dieback of a leighton green hedge

Dieback of a leighton green hedge


Use of a fungicide with active ingredients of phosphorus acid or copper oxychloride has good results when diagnosed and applied early. Best application is via a foliar spray, if this is not practicable we have found tree injections and soil drenching applications have also achieved good results.

Preventative measures such as regular feeding and watering and reducing the chances of wounding, are advisable. Any infected branches can be pruned 10 cm below the canker to prevent infection spreading to the main stems. All tools should be sterilised before and after use with alcohol or dilute bleach. Severely diseased trees should be removed and destroyed. Please avoid mulching affected trees as the spores will be dispersed into the air and the mulch will carry the spores when it is spread. Although not yet widespread on the Central Coast NSW trees, care should be taken not to spread the disease.

We have performed tree removal on severely affected trees on the Central Coast and then done pruning of the affected tree parts on adjacent trees. We have then improved the tree health via fertilising, mulching and watering and also applied a fungicide. We have done follow up treatments of the fungicide, and this has saved many of our customers beloved screening cypress trees.

Please ensure your Arborist has experience in treating this disease before engaging their services to treat cypress canker. This also goes with tree removal, as proper disposal is requires so that the disease does not spread to other trees in your garden.