And even an olympic tree can be overwhelmed by a huge wound. Sometimes, the barrier system is breached by the infection. When this happens, the tree begins the process over again in a new location. Infections are often transmitted by insects which feed on trees. If the insect chews into woody tissue, protective barriers are initiated, whether or not an infection occurs.
Trees have protective organs located at the juncture with every branch.
These specialized groups of cells, called branch collars, manufacture antibiotic chemicals. They form an invisible protective barrier an inch or two inside the trunk. The branch collar is usually an enlarged, swollen area which is fairly obvious. It is important not to cut this off when pruning. Generally, circular woundwood growth around a pruning cut means a it was correct, and oval shaped woundwood means the branch collar was cut.