My Maple Tree Has Some Type of Green Fungi

Disorder Identification

• The funguslike growths on maple trunks or branches are actually densely growing, non-flowering plants referred to as lichens. Lichens come in different colors including various shades of green, gray, red or brown and different textures. Some lichens have crustlike texture, some have leafy filaments growing from their upper surface and certain lichen varieties are straplike in growth.

Description

• Lichen forms from the mutual cooperation of an algae and a fungus that depend on each other for survival, creating what is called a symbiotic relationship. The fungus is responsible for absorbing atmospheric moisture and minerals while the algae produces the vitamins and carbohydrates necessary for growth. Lichens reproduce from broken segments or fragments or when spores of the fungus in the lichens germinate near a companion algae.

Damage

• Contrary to common perception, lichens don't kill trees. This appears to be the case since declining trees frequently have lichens on them. Lichens are not pathogenic in nature and do not penetrate tree tissues. The plants only use the tree surface for support and appear just as commonly on non-living surfaces like fences, rocks and cut logs. Trees that are growing in polluted areas with high levels of ozone, sulfur dioxide or acid rain are also more prone to lichen growth. An unusually heavy layer of lichens may cause an already unhealthy tree to decline further.

Management

• The best way to avoid lichens is to make sure the maple tree is in good health. Provide adequate irrigation and fertilization to improve strength and reduce stress. Weak trees with excessively thinned canopies also encourage lichen growth by providing them sunlight for growth. Chemical control options include copper-based fungicides sprayed directly on the lichens.