Why Trees Get Sick

By Nancy Penrose

There are many reasons why a healthy tree can get sick, such as pests, injuries, disease and poor maintenance. Even the environment can adversely affect a tree’s well-being.

There are several ways to tell if a tree is doing poorly. Some of the more obvious signs include areas of decay and evidence of infestations. A tree may also have health issues if it isn’t growing or has prematurely dropped its leaves. Other indicators of illness include early ripening, wilting, loss of color, and trunk or branch abnormalities.

Trees can become infected from pests such as aphids, root weevils, leafrollers, spider mites and the codling moth. The pests will either burrow into the tree or start feeding on it. Sometimes they do both.

Trees can also get blight, a type of fungi or bacteria, and root rot. When a tree has blight, it will initially turn brown and then die. Root rot is also a fungal pathogen and can kill a tree. Indicators of root rot include dieback and foliage discoloration.

Storms can cause broken branches, split branch forks and snapped stems. When wood breaks and becomes exposed, it can become infected by microorganisms. These types of injuries, depending on where they occur, can also damage the tree’s overall health.

Trees can also be injured by bad pruning, garden equipment like lawnmowers and weeders, as well as foot traffic if it’s near the tree’s roots.

Environmental factors that affect the health of your tree include pollution and herbicides that drift in from other locations.

Trees can also have a difficult time adapting to a new environment. If you’ve recently planted a tree or had a tree transplant and it isn’t doing well, check for soil and drainage issues, as well as too much or too little light or water.

Trees are an investment and will need proper maintenance and care to survive. As professional tree arborist, specializing in big trees, we can answer all of your questions about tree care and how to keep your trees healthy.

Nancy Penrose is owner of Big Trees Inc. (, (tree nursery Snohomish, WA), one of the largest Seattle tree nurserys (visit Big Trees Planting Service page at, specializing in large trees for sale and tree transplanting. For more tips on tree landscaping go to See our video at and connect with us on Facebook at