Forest Health: Overview

Forest health is affected by insect outbreaks, diseases, invasive species, regeneration, fire ecology, natural disturbance, and many other factors.

Fungal growth on birch: Jim Frazier photo
Fungal growth on birch: Jim Frazier photo

Not all insects and diseases are bad. Native insects and diseases are a normal part of a healthy forest. An example is the periodic defoliation events from forest tent caterpillars (sometimes called armyworms). Minnesota forests evolved in the presence of these bugs, and they recover quickly from outbreaks.

On the other hand, non-native, introduced insects, diseases, and plant species pose a serious threat. Invasives must be addressed quickly. Diseases like Dutch elm disease, shrub species like buckthorn, and new invasive insects like Gypsy moth and emerald ash borer can cause serious forest health problems. It’s critical that landowners learn to identify these species quickly and keep their woodlands healthy and free from invaders to the greatest degree possible.

The pages in this section are designed to provide basic information about forest health issues in Minnesota. Probably the best source of forest health information in Minnesota is the Forest Insect & Disease Newsletter, published by the MN DNR Division of Forestry. You can also watch recorded presentations by MN DNR forest health specialists here.

As more and more invasives enter our woods, forest health can seem daunting at times. But it’s important that we all maintain vigorous, healthy native woodlands to the greatest degree we can. Most forest health threats are far easier to prevent than to eradicate once they’re established. Good luck! Your neighbors, as well as future generations, will thank you for it.


Eli ‘s work addresses Minnesota forest ecology & management. He’s based in St Paul.

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