Tree Care and Maintenance

Seasonal Tree Care Tips: Fall 2019
Insects and Diseases

Images courtesy of: Christine Buhl, Oregon Department of Forestry,

Signs of sequoia pitch moth (Synanthedon sequoiae) on ponderosa pine.

Insect infestations and pathogen infections can threaten the health of your trees. Knowing what tree species you have can help you understand what types of insects and diseases it is susceptible to, and with proper care and maintenance you can manage to prevent problems before they start. Becoming familiar with what is normal for your trees can help you recognize abnormalities early on so that you can take action before it’s too late.

If you recognize abnormalities, the next step is to identify the symptoms (e.g., discolored foliage or top dieback) and look for signs (e.g., insect bore holes or mushrooms). Abiotic problems (caused by non-living organisms, e.g. drought stress or sunscald) generally follow a pattern or uniform display, whereas biotic problems (caused by living organisms, e.g. pests and pathogens) show symptoms in a more scattered or random display throughout the tree or groups of trees. Consider contacting a certified arborist who specializes in plant health care to help diagnose the problem. Once the problem is positively identified, a treatment protocol may be selected. As in the medical field, “treatment without diagnosis is malpractice.”

Not all insect and disease problems have a cure or are necessarily life-threatening. In fact, a variety of common issues are more aesthetic than detrimental, such as alder flea beetle which can skeletonize leaves, or sequoia pitch moth which is commonly mis-diagnosed as bark beetle. Still, your tree may last for many more decades with pruning, systemic injections or cultural practices to manage plant health by optimizing site conditions (e.g., reducing soil compaction and improving soil health, mulching and supplemental watering).

Visit these sites to learn more about managing your trees to prevent and treat insects and diseases:

 Please check back for more seasonal tree care and maintenance advice!

Link to Tree Care and Maintenance Archives


Summer 2019: Drought Stress Revisited

Spring 2019: Trees and Construction

Winter 2019: Topped Tree

Fall 2018: Autumn Leaves

Summer 2018: Emerald Ash Borer

Spring 2018: Pruning Young Trees

Winter 2017: Tree Related Storm Damage

Fall 2017: New Tree Selection and Planting

Summer 2017: Trees and Turfgrasses

Spring 2017: English Ivy Removal

Winter 2017: Recognizing Tree Risk

Summer 2016: Drought Stress

Fall 2016: Preparing Trees for Winter


Additional Tree Care Resources:

National Arbor Day Foundation The Morton Arboretum
Oregon Department of Forestry Tree Care Info
ISA Find an Arborist Oregon Community Trees
Oregon Department of Forestry Alliance for Community Trees


Right Tree in the Right Place

Use this handy guide for assistance in choosing the right species of tree based on the constraints of a site, such as overhead wires, narrow plant strips, and proximity to structures.

"Right Tree Right Place" - helpful information such as "Use this guide for assistance in choosing the right species of tree based on the constraints of a site, such as overhead wires, narrow plant strips, and proximity to structures."

"Master Plant List" - a guide to the plants that are acceptable for mitigation requirements in Lake Oswego.