tree moss killing tree

Asked August 18, 2019, 3:47 PM EDT

There is a moss / lichen that seems to be killing the branches on my Japanese Snowbell trees in front of my house. It seems that once it gets thick enough on the branch, the branch dies. What is this and is there something that I can do to manage / kill it?

Benton County Oregon trees and shrubs

1 Response

Lichens and mosses get a bad rap and are often accused of causing trees and shrubs to decline. The truth is that lichen and moss typically begin to grow on plants that are already experiencing poor health. Lichens and mosses provide many benefits, such as a nesting, cover and food source for wildlife. For example, lacewing larvae -- beneficial predators that feed on undesirable insects -- use lichens as a protective cover. Despite providing many beneficial aspects, lichen and moss can become problematic in cases of heavy growth. For example, lichen and moss growing on trees and shrubs add extra weight -- which can lead to branch breakage -- and block the leaves' ability to process sunlight into energy.

Manual Removal

Certain types of lichens and mosses can be manually removed from small trees and shrubs. Manual removal may require a ladder if the lichen or moss is growing in a hard-to-reach area. A friend should be present to hold the ladder steady while you are on it. When removing the lichen or moss, refrain from pulling it off the tree or shrub and instead gently lift it up off the plant. This will avoid damage that can occur from jerking the lichen or moss off the branches. Furthermore, wait until the dormant stage of the tree or shrub to manually remove the lichens or moss. This will help prevent damaging buds during the removal process. Alternatively, you can lightly prune the tree and shrub limbs covered in lichen and moss to help stop them from spreading. Removing lichen and moss from large trees can be a difficult task that requires a cherry picker or bucket truck. This is often too costly for homeowners; leaving the lichen or moss in place should be considered.

Chemical Removal

Certain species of lichen and moss can be controlled with a mixture of 6 tablespoons of liquid copper sulfate diluted in 1 gallon of water when applied during the dormant season. When applying the copper sulfate, thoroughly cover the entire lichen or moss to the point of runoff. Before using any chemicals to control lichens and mosses, read the specific instructions printed on the label. Following the manufactures recommended directions will increase the chemicals effectiveness and help prevent injury to the tree or shrub.

Prevention

Prevention is the best defense against lichens and mosses; ensuring the trees and shrubs are healthy and vigorous will go a long way to controlling these unwanted organisms. To keep the plant healthy, always follow the growing requirements, including proper lighting, fertilization and watering, for the specific species. In addition, ensure the tree or shrubs are growing in fertile soil, which will stimulate growth and help to inhibit lichens and mosses. Many times, merely improving the health and vigor of the infested tree or shrub will control the lichen or moss growing on the plant.

Hope this helps!