The contribution describes the complex changes in trees after wounding. Summarily four phases of defense reactions according to the CODIT principle are presented:

Phase 1: Invading air. As a reaction on the invading air the tissue at the wound edges dies.

Phase 2: Invading of microorganisms (e.g. decay) into the dead discolored tissue.

Phase 3: Spread of mircoorganisms in the wood. Especially in older tissue the reaction zone can be breached.

Phase 4: Encapsulation of the microorganisms. Wound closure progressing from the wound edges encapsulates the infected wood. Once the decay is enclosed the microorganisms die since needed oxygen is no longer available to microorganisms.

The encapsulation of wood infected by fungi is the survival principle for trees.

The presentation shows the wound reactions in different tree species and in different types of wounds and gives recommodations for arboricultural practice.

The CODIT principles are based on results of research from different institutions in the world. The concept is published in Germany (Das CODIT Prinzip). The English version is available now at ISA Central Bookstore and the author will be available after his talk to sign your copy..