Expert: John Cawly - 4/24/2007

Question
the pineapple guava tree has a light green fungus at the trunk of the tree. the tree is planted in a raised bed, recently mulched, and watered alternating days. HELP! thanks, bobby

Answer
Hi Bobby,

I am not certain that what you are seeing is a fungus.  Fungi rarely are that color.  There are lichens (a combination of algae and fungi) that are found on many tree trunks, and depending on the amount of algae in the lichen can appear a shade of green.

There are many, many fungi that are associated with decomposition, and from time to time these will be apparent in mulched beds as the mulch itself is decomposed.  

If you can, describe with as much detail as possible, the size of the "fungus", the shape (does it have a definite shape? or is it more like a blob? does it contain threadlike structures?  Can you see dark tufts or spores?)  

Lichens may appear leaflike with curly wavy edges.  They can also appear as filaments, threadlike.  At times they will have small "cups" which contain sporing bodies.  

Check out the following website to see photos of lichens.  If these look in any way familiar, you have a lichen growing at the base of your tree.  Lichens do no harm to the plant as they use the trunk for support.  

Here is the website:

http://www.lichen.com/biology.html