lichen

Lichens produce their own food using sunlight energy and do not feed on the tree bark.

Question: My tree has started getting these bushy growths on it. Can you tell me what they are and do they mean my tree is dying?

Answer: It looks like your tree has several different types of Lichen growing on it. There are at least 13,000-17,000 species of lichen living throughout the world. When identifying lichen, we typically rely on the descriptive appearance, size, shape and color of the lichen body and the reproductive characteristics. Lichens are typically placed in three main groups based on their body forms and features: crustose (crust-like), foliose (leaf-like), and fruticose (tube or beard-like strands). The growth you are referring to is a type of fruticose lichen, which can be a miniature shrub-like lichen. It also appears that you have lichen growing on top of other lichen.

Lichen is composed of two or more dissimilar organisms that form a mutually beneficial relationship to produce a new vegetative body that is called a thallus. The life forms are composed of a fungus and most often a green alga with perhaps a blue cyanobacterium. The fungal filaments make up about 80 percent of the lichen body. The fungus forms the outer surface to provide support and protection, absorb moisture and collect minerals from the air. Since the fungus cannot produce its own food, it is dependent upon another life form to provide that essential function. Green algae and cyanobacteria possess the green pigment chlorophyll that is essential for photosynthesis to make food. When surrounded by the fungus, they provide the food to enable the lichen to exist and sustain itself in a suitable habitat.

Unlike plants, lichens do not have leaves, stems, or roots, or a waxy outer cuticle to control body water content. Lichens continue to grow during periods when dew, mist and rain water are present. A summer dry period can cause them to become dormant until the next rainfall. Miniscule mineral particles that are carried by the wind during wet conditions are dissolved and absorbed by the lichen. Our weather conditions over the last few months have given lichen an ideal environment to stay in active growth.

Lichens produce their own food using sunlight energy and do not feed on the tree bark. The lichen bodies are attached to the outer tree bark and remain on the surface. Their rhizines (multicellular root-like structures arising mostly from the lower surface) typically do not penetrate deep enough into the inner bark, and cause no harm to the trees they inhabit.

In contrast, certain fungi operating independently outside a lichen body will penetrate tree wounds or dead wood and feed on the host plant. The filaments of the fungal body will reside inside the tree tissue with only the fruiting bodies visible on the surface.

Lichen grow harmlessly on tree trunks and no control is needed. In fact, presence of lichens on healthy trees should be welcomed as likely positive indicators of lower levels of air pollution and a reasonably good quality of atmospheric conditions in your neighborhood. They do not typically grow on younger, rapidly growing trees, because the bark is shed too quickly for them to have time to spread. Lichen typically thrive on trees that are mature, have less vigorous growth, or are in decline.

The lichen themselves will not cause decline, but they may be a good indicator of the overall health of your tree. An abundance lichen presence concentrated on damaged or dead wood, as your sample appears, may be a warning of present or impending invasive disease or decay caused by fungi, bacteria, viruses or insects and may require corrective action. It may also be an indicator of significant environmental stress. When they are found on dead or dying branches, particularly when accompanied by thinning of the tree crown, they have located themselves there because of the greater availability of light from leaf drop.

In the months ahead, you should monitor the tree for other signs of decline such as lack of vigor, small leaves, early leaf drop and dieback of twigs and branches. Your local extension office can provide you with a list of certified arborists who can assess the tree on-site and make recommendations for removal of dead branches to encourage growth, cultural changes or fertilization.

For more information on lichen, please see Rutgers Fact Sheet 1205 or contact your local extension office. Do you have a plant problem you need diagnosed? You can send or drop off a sample at 6260 Old Harding Highway, Mays Landing, NJ 08330.

Guidelines for submitting a sample: 1. The sample should be as fresh and complete as possible, with examples of soil, roots, stem and leaves. When this is not possible, as with trees or a lawn, a picture can be helpful. 2. The sample should be representative of the symptoms, in the diseased or dying stage but not completely dead. Once a plant is dead, microorganisms that decay organic matter start to grow, making it difficult to isolate what originally caused the plant to die. 3. The sample should not be too large or too small. Pieces the size of an arm's length or smaller are ideal. When a sample consists of only a few leaves, a single seed/pod, or pieces of bark, it is difficult to make a good diagnosis. 4. Samples should be taken before treatment with any pesticides. Pesticides prevent growth of insects and pathogens and may prevent us from finding the cause of the problem. Atlantic County Master Gardeners are available 9 a.m. to 1 p.m. Monday through Friday, but samples may be dropped off any time between 8:30 a.m. and 4:30 p.m. Atlantic County residents can contact the Master Gardener Helpline at 609-625-0056. Cape May County residents can call 609-465-5115, ext.3607.

Do you have a gardening related question you would like answered here? Please forward your questions to Belinda Chester, Master Gardener Program Coordinator, Rutgers Cooperative Extension Office, 6260 Old Harding Highway, Mays Landing, NJ 08330. You can also submit questions at Rutgers-atlantic.org/garden or email them to currents@catamaran.com; please include “garden question” in the subject line.

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