Collar or crown rot is caused by a fungus that invades a tree’s lower trunk or upper roots and begins to block the tree’s vascular system. The infection point often develops as a canker which causes a girdling (strangulation) of the tree as it spreads.
Crown rot and collar rot refer to the same disease, except they have different names depending on the location of the infection (on the root stock or the scion portion of the graft union).
The most obvious symptom found on an infected tree is a partial or complete girdling of the trunk. The diseased tissue at first appears orange and reddish-brown, then becomes browner as the rot and decay advances. The disease spread is most prevalent in areas that have poor drainage or standing water.
It is important to ensure that there is proper drainage in areas of collar or crown rot outbreak or in susceptible areas. At first sign of the disease treat with Agri-Fos Systemic Fungicide. Repeat treatment as needed, depending on the level of disease. Prune and remove cankers that have developed. Be sure to properly sanitize the pruning knife during the canker removal process.