Coral spot (Nectria cinnabarina) is a fungus with a coral pink pinhead pustules or very small browish red pin heads. It bursts through the bark on dead and dying stems or twigs. It enters the wood through old pruning wounds and can be transferred from pruning tools. It causes the death of individual branches and is mainly a saprophytic fungus but could be linked to the spread of dead tissue and cause of dieback and bark death. It is commonly found on Maples, Beech, Lime, Apple, Horse Chestnut, Walnut, Elms and some Conifers.
The above was found on a maple branch and was removed to reduce the potential for further spread of the fungus along the branch. It potentially entered from the dead stub left on the end of the branch, but hopefully should not affect the living branches as being a saprophyte it feeds on dead organic matter.
If found on your bonsai trees then:
- remove the dead, dying and infected limbs and burn or dispose of them.
- disinfect all pruning tools and this should be part of your normal practice when working from one tree to another.
- maintain good tree health
- regularly check the status of your trees health and look out for all pests and diseases
- Improve the airflow around your trees
- check the soil medium that it is not water logged
- improve the drainage if necessary and any moss or weed on the soil surface to improve the gaseous exchange for the roots in the soil over winter