Lichen Removal from Apple Trees

Development

• Lichen is a slow-developing organism that often goes unseen through its early years. It firmly attaches itself to cool, damp surfaces that have partial shade with some ventilation. It is commonly found on ailing and diseased trees that have begun to lose vigor. The fungi and algae support one another as the fungus provides the water for growth while the algae create the food. This self-supporting system allows the lichen to grow without the help of the apple tree’s nutrients.

Damage

• Although the lichen does not feed on the apple tree, its development can result in additional loss of vigor and infection. Lichen develops across damp, cool surfaces. As the lichen expands, it can lock moisture between the wood and lichen. This locked-in moisture can result in fungal and bacterial infections, including wetwood infections and wood decay. Also, lichen that blocks the sunlight to foliage can cause leaves to die back, wilt and defoliate from a tree.

Prevention

• A vigorously growing, healthy apple tree is best able to prevent lichen germination. Prune your apple tree in the early spring to remove water sprouts and suckers from the canopy and base of the tree. Thin the interior branches to promote good ventilation and sunlight penetration throughout the apple tree’s canopy. Feed the apple tree in the early spring with a well-balanced, slow release fertilizer, such as a 10-10-10 or 20-20-20 combination. Always keep the fertilizer at least a foot away from the trunk of the apple tree to prevent chemical burn and resulting growth stunt. Harvest the entire apple tree at the end of the growing season to reduce the potential of fungal development from the mummified apples.

Removal

• Lichen develops firmly across an apple tree’s surfaces. As a result, removing lichen from an apple tree can be difficult and, at times, damaging. Lichen that has developed on an apple tree’s branches and stems can be removed during the tree’s regular pruning sessions. Use sharp, sterile shears to remove the branches and always sterilize the shears between each cut to prevent spreading the fungi and algae to healthy areas. There are no effective chemical treatments to eliminate lichen development. Lichen that has developed on the base and trunk of a tree can be cut out of the woody area. However, the deep cuts and open wounds can introduce fungal and bacterial diseases that can harm or kill the apple tree.