Brief Description
Help sheet on identifying tree issues
Topics
Full Text
Common organisms growing on trees can be classified as benign (epiphyte) or harmful (parasitic). In the case of benign organisms like ball moss, Spanish moss, or lichen, the degree of infestation is usually not related to the health of your tree. In fact, you may notice these same epiphytes growing on power lines! If you notice a parasitic fungi like Ganoderma or Armillaria
acting on your tree, this can be an indicator of an unhealthy tree.
Identification
Organisms that are classified as benign will not pierce the outer bark of a tree and as such do not disrupt the inner workings of water and sugar movement. Instead, the nutrients and moisture that the plant needs are obtained directly from air, rainfall, and debris that accumulate around the point of attachment. Parasitic agents such as mistletoe, will typically be deeply imbedded in the inner wood of a tree, or in the case of parasitic fungi will be feeding on the decayed wood in your tree.
Prevention
The frequency of parasitic fungi like Ganoderma and Armillaria can be reduced by not wounding or injuring the root system and stem of your tree. Wounding these areas substantially increases the likelihood of infection. These fungi feed on decay, which is often a consequence of injury. The prevention and reduction of epiphytes and parasitic plants like mistletoe are difficult on a large site, but control on single trees is possible.
Control
Although not necessary, in extreme cases where control of an epiphyte is desired, you can hand pick each epiphyte, prune dead branches on which epiphytes typically grow, or spray with a chemical like Kocide 101. Control of mistletoe is typically not warranted, but a registered plant growth regulator called ethephon (Florel) may be of use in significant infestations.
With parasitic fungi like Ganoderma and Armillaria, there is no effective control once it is established within the tree. Hire an ISA Certified Arborist to assess the extent of decay and help determine your next steps.