While perfectly healthy trees sometimes succumb to pest or disease problems, more often a tree becomes vulnerable to these problems due to abiotic (non-living) factors such as environmental, mechanical, or chemical stress. A few examples of these stressors include:
- Chemical stress – over-fertilization and de-icing salt contamination
- Environmental stress – drought conditions, excess soil moisture, too little sunlight, extremely cold temperatures, poor soil quality, and soil compaction
- Mechanical stress – damage from lawn equipment or improper pruning practices and construction damage of severed roots or trunk wounds
Avoiding Tree Stress
Conditions in the urban environment are very stressful for trees. Sometimes stressful conditions in urban areas impact a tree’s health more than the same stressful conditions that the tree species may be adapted to in its natural setting. By keeping your trees in healthy condition, the chances of enjoying the benefits of a tree’s full lifespan are greatly increased. Ways to reduce the chances of stressing your tree, thereby making it less vulnerable to insect or disease problems, stress, decline, and death include:
- Apply mulch under the drip line of trees to conserve moisture, regulate soil temperature, and provide nutrients. Make sure not to pile mulch against the trunk, which can lead to decay.
- Contact an arborist about constructing a Plant Health Care (PHC) plan, which will provide a pro-active approach for maintaining the health of a landscape. For more about PHC, view the International Society of Arboriculture's information on Plant Health Care.
- Do not over-fertilize.
- Do not pile fill soil on top of a tree’s root system and avoid storing equipment or building materials under the drip line. These actions can reduce oxygen availability for tree roots, which causes suffocation and decline.
- Do not trench or cut roots under a tree’s drip line if the intent is for the tree to remain on site.
- Hire an arborist, a professional who is trained in proper tree care, to perform tree maintenance for you. Arborists that are certified by ISA have demonstrated knowledge and experience in the practice of arboriculture (tree care). You may find a certified arborist in your area at the Trees Are Good website by searching with your zip code.
- Never "top" a tree. This practice removes far too much food producing material and leaves the tree in an extremely stressed state. The sprouts produced after topping are a tree’s attempt at producing enough sugars to overcome the stress. The tree may continue to live for a time but will be far more susceptible to other agents and is by no means healthy after this point.
- Provide water for your trees during periods of extended drought in the amount of five gallons weekly per inch of trunk diameter. Newly planted trees should be watered consistently for the first three years after planting. At the same time, beware of overwatering from turf grass irrigation systems. Trees do best with infrequent, deep waterings.
- Prune trees only when it is necessary for structure, health, and safety purposes.
- Remove vines, turf, or competing vegetation surrounding the tree’s trunk.
- Use proper pruning techniques (cuts and tools) and never remove more than one-third of a tree’s branches within the same year. View the ISA website for useful information about pruning mature trees and pruning young trees.
- When planting a tree, make sure that the root flare is not buried. The root flare is the part of a tree where the base of the trunk meets the root system. The trunk flares out a little bit at this point. The base of the root flare should be level with the soil surface after planting.