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Q. We are enclosing some pictures that we took of some of our trees, which have been attacked by disease. We were wondering if you could tell us what it is and how to treat it. I'm afraid it will spread to our other trees and eventually kill them. The types of trees are maple, apple, oak and poplar. We appreciate any help you can give us.
A. I have good news and bad news. Your trees have two types of growth showing in these photos. The good news is that neither spread to other healthy trees.
More good news is that the flatter, grey-green growth is a colony of lichens - harmless symbiotic (mutually beneficial) organisms composed of a combination of fungi and either algae or cyanobacteria. Together, they live as one organism and are only using the bark of your tree for anchorage; lichens are not parasites. More information on lichens can be found at http://www.ppdl.purdue.edu/PPDL/expert/Lichens.html.
Some not-so-good news is that the creamy-colored growth that protrudes a bit from the trunk is called shelf fungus and lives on old, usually decaying, trees. While this fungus does not cause disease itself, it is an indication of serious decay problems below and can further weaken the tree. The fungus is less serious than the principal cause or causes of decay. Affected branches can be pruned out, but there's nothing that can be done when the decay is on the main trunk. The tree can continue to live for quite a few more years, but eventually it will need to be removed.
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Q. I've inherited a distressed Norfolk Island pine. It was in an office, which was very dry, and it had been neglected, even as to its watering. It now is in my living room, and I would like to do what I can to get it back to health. It is sparse from the middle on up. I have removed all of the dead branches. It measures approximately 48 inches from the top of the soil to the top of the branches and measures about 48 inches at its widest point. The pot that it is in is 12x16 inches and does not have any drain holes. It is not full but is very wide. Should I prune the tree? I have attached a picture. What is the best course of care?
A. Unlike many other plants the Norfolk Island pine is not able to replace the gaps in the middle. Any branch that has dropped needles or whole branches that have died will remain bare. So there is no way to prune it that would result in desirable regrowth.
The most immediate need is to repot into a container that allows excess water to drain away from the soil. However, given the bare areas in the middle, you might want to consider either starting over with a new plant or, if you really want to save this particular plant, you might try to root the cut top and discard the bottom. Norfolk Island pine cuttings can only be taken from the top of the central leader stem; cuttings from the lateral branches will not form a new leader.
More information on the care of this plant is at http://www.hort.purdue.edu/ext/norfolkislandpine.html and on how to take cuttings at http://www.hort.purdue.edu/ext/HO-37web.html.
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