There are several pests and diseases that can cause a tree to wither, lose its canopy, or otherwise become ill. Precautions should be taken to protect trees from infection, as a sickened tree can lose structural integrity or pass the infection to other nearby trees. Ash trees, for example, can become infested by Emerald Ash Borers, which causes structural damage to the tree and can easily spread to other plants in the area.
Parasites and other infections are not, however, the only cause of plant illness. Environmental factors such as temperature change, humidity and rainfall can all affect trees in negative ways. Consider, for example, root rot. Root rot can be caused by several factors, some of which are environmental in nature, while others are caused by other organisms. The primary cause of root rot in trees is often an overabundance of water, which results a deprivation of oxygen in the roots. Since oxygen in the soil is needed for a plant’s cells to complete their respiration, an overabundance of water will often lead to cell necrosis in overwatered plants.