Over the last several days I have fielded several calls from homeowners concerned about a fuzzy moss or “fungus” growing on plants and trees. The plants are being blamed for damaging or killing branches or in some cases entire trees. The moss is actually a form of Lichen. Lichens are a plant composed of a fungus and algae. The two separate organisms partner to contribute to the development of a hardy adaptive plant that grows not only on woody plants but also on soil, rocks, and other non-living organisms - even fence posts.
There are 3 types of lichens: 1) Crustose forms which are flattened against limbs and vary in color but most often brown and light greens 2) folicose forms which produce a wavy leaf like fold outward from the limbs, and 3) fruiticose lichens which are highly branched finger or hair like in shape and most often light green to grey colored.
Lichens are often blamed for the decline and/or death of numerous plants in landscape and orchard settings. But, they rarely contribute to poor growth, and even more rarely to the death of entire plants. The lichens are just easier to notice as a result of the declining plant growth and presence of leaves. The lichens are simply much more obvious to the eye on a weak or dead limb. They are most numerous on limbs and trunks of mature trees in full sun, especially those with thin canopies. Most will not survive in heavily shaded areas.
Lichens generally are not considered plant pathogens. They reproduce when small pieces break off of existing lichens and begin to expand their growth as a new plant. Fragments can be spread by wind, splashing water, animal movement, and even humans. Lichens can also develop when fungal spores germinate on or near algae.
The most common thing people want to know about lichens is “How can I get rid of them?”. Good plant vigor is the best means to defend against lichens. Heavy infestations are usually found on plants in declining or poor health. Following recommended watering fertilizing and pruning practices will promote healthy plants which tend to avoid problems with lichens. Light pruning of affected limbs will remove some lichens and promote new plant growth which may help with shading to further help with preventing establishment of additional lichens. Trees and shrubs in extremely poor condition will often not respond to enhanced care and may need to be replaced. Presently there are no pesticides registered for control of lichens commonly found on trees and shrubs.
For more information, contact your local County Extension Office.
Thanks to Kevan Tucker in Clarke County for the original article.
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