See:
Maple (Acer spp.) - Nectria Canker
Cause Nectria cinnabarina and N. pseudotrichia, fungi that have been reported in the US and observed in Oregon. These fungi invade trees through wounds and injuries including winter injury, drought damage, sunscald, leaf scars, cracks in the twig axil, or senescent low branches. Spores are splash dispersed from fruiting bodies that exude spores in rainy weather or during irrigation.
Symptoms Girdling cankers form on twigs and limbs followed by dieback. Cankers appear as slightly sunken areas which are not obvious until striking, orange-red, fungus-fruiting structures (perithecia) develop in large numbers in the cankered area.
Cultural control
- Remove and destroy affected twigs and limbs. Do not leave them on the ground between rows; carry them out to a burn pile or bury them completely into the soil.
- Prune during dry weather near the end of the dormant period.
- Avoid wounds.
- Avoid leaving pruning stubs when removing rootstock top growth. Make a clean cut with a sharp tool, which will heal promptly.
- Maintain tree vigor through proper fertilizing and watering.
Reference Fowler, M. E., and Stevenson, J. A. 1944. A canker and some decay fungi on mimosa. Phytopathology 34: 985-987.