Insect pests and diseases are among the greatest challenges to maintaining a thriving urban and community forest.
Many of the most severe problems are caused by invasive species--insects, diseases, or even other plants that were brought from one location to another where they did not originate. Since local trees did not evolve alongside these organisms, they did not evolve defenses.
Invasive species of insects, such as the emerald ash borer and the gypsy moth, that feed on trees or viruses or bacteria that infest them, such as Dutch elm disease, can kill trees directly. Invasive species of plants can reproduce so rampantly that they out-compete more desirable trees for space, water, and nutrients or prevent regeneration.
The Morton Arboretum's Community Trees Program provides extensive oureach and information for governments, tree professionals, and property owners seeking to safeguard their trees or to cope with the impact of an infestation, which can be devastating.