leyland cypress trees dying

Asked July 15, 2018, 5:13 PM EDT

is there a fungal disease killing leyland cypress trees or other pines in the annapolis md area?. Any treatment available?

Anne Arundel County Maryland

1 Response

Leyland cypress trees are known to have their problems. You do not mention the age of yours but they are not a long-lasting evergreen in our area.

Leyland Cypress was the 'go to' landscape plant for many years for evergreen screening in yards. In recent years it has become evident that they look great for the first 15 years or so, and then start to decline. Very often we see them planted too close together, which leads to competition for water and nutrients. As the trees mature, lack of sunlight leads to the decline of interior branches.

Stressful conditions like drought or cold winters can make Leyland cypresses susceptible to different insect pests and diseases. Common problems include 'winter burn', which is a browning desiccation injury from drying winter winds. We have seen a lot of this type of injury in Leylands this year. Here is a recent article from our plant pathologist about this: https://marylandgrows.umd.edu/2018/04/11/why-is-leyland-cypress-turning-brown-winter-took-its-toll/

Much more serious are canker diseases and needle blight. Here is a page about these diseases and the symptoms to look for: http://extension.umd.edu/hgic/plants/seiridium-and-botryosphaeria-canker-leylands-trees No fungicides are effective for these diseases.

In addition, bagworms are an insect pest of Leyland cypress. If not controlled, these can also lead to browning and decline. https://extension.umd.edu/hgic/bagworms-trees-and-shrubs

For winter damage, there is not much you can do other than wait to see if new growth will develop then prune out areas that haven't recovered. Prune only to where there is green growth. (Do not cut into the wood with no foliage. It will not regrow.) Keep the trees well watered and mulched in times of drought. Avoid pruning when the trees are damp.

The bottom line is that Leyland cypresses look good for about 10-15 years and then they start to decline.

Pine trees also have their problems. They are also prone to winter burn and if they are planted near a road sustain damage from road salt. They can be attacked by bagworms and bark beetles. The weather has also been playing a role in the decline of trees. Overall our seasons are warmer, with periods of abundant rain then droughts. This stresses trees out making them more susceptible to pests and diseases.