Improper Pruning

• Not all threats come in the form of natural or environmental threats. Trees are routinely damaged by those with the best of intentions. Homeowners and even professional tree cutters can cause serious damage and leave a tree open to erosion just by pruning it improperly. Although pruning dead limbs regularly will benefit the tree, cutting into the main trunk or leaving large open gashes on substantial branches leave unprotected areas that attract predators of all sizes. Fighting off a serious infection or infestation can cost a tree too much energy, causing its death in the next cold season.
  
  

Over-Browsing

• Several animals browse on leaves and twigs from trees and several more feed on the root systems of trees. While losing a few leaves or root offshoots will not kill a mature tree, over-browsing can cause serious damage, slowing a tree's growth and seriously damaging its energy production systems.
  
  

Fungus and Mold

• Blight, leaf spot and other mold and mildew infections take hold of a tree, weakening the immune system and causing physical damage to trees including the wilting of leaves, erosion of bark and even the eventual death of the tree. Prevent fungus and mold by treating the tree regularly with fungicide. If the tree is already infected, ensure it receives proper nutrition through fertilizer and prune the infected area as soon as possible.
  
  

Infestation

• Larger pests than mold also cause damage to trees. Insects such as termites infest the inside of trees, cutting large passageways through the tree's interior. These passages undermine the strength of the tree when standing up to the wind and other elements. In addition, cut passageways inside the tree cause interruptions in the flow of xylem and phloem through the plant's vascular system. The result is a weakened tree that is structurally unfit and capable of collapsing in the first intense storm.
  
  

Malnutrition

• Many non-native trees that are planted in less than ideal soil die of simple malnutrition when their planters move or stop fertilizing them. Ensure your trees have an adequate supply of plant food and water.