blooming flowers climber in tree to prune beneficial mushrooms close up of lady bug on leaf japanese maple being pruned

Top 20 Tree & Shrub Problems in the Pacific Northwest

Spider Mites

Very tiny, closely related to spiders, feed on arborvitae, conifers, roses, perennials, and euonymus. They suck out plant sap and chlorophyll resulting in foliage looking, speckled, yellow, or bronzed cast. Leaves may drop prematurely.

Root Weevil

Adults feed on foliage of over 100 plant species including: perennials, strawberries, salal, Oregon grape, azaleas, rhododendrons, viburnum davidii, yew and spruce. Larvae feed on roots killing small plants.

Leaf Rollers & Tent Caterpillars

Larvae feeding on foliage of fruit ornamental trees in the spring and summer, causing defoliation.


Sucking juices of shade trees; oak, maple, birch, beech, elm, tulip trees, results in defoliation and drips sticky honeydew.

Insect Borers

Many different species attacking weak or dying trees, feed under bark or in sap wood of trees.


Hard or soft bodied insects feed on bark or leaves by sucking plant sap, infested trees drip sticky honeydew.

Codling Moth

Worms in fruit of apple and pear trees.

Brown Blossom Blight

Disease on fruit and ornamental cherry and plum trees causing leaf and twig blight.

Dogwood Anthracnose

Disease, causing leaf and twig blight.

Phytophthora Root Rot

Fatal disease on rhododendrons and Port Orford cedar trees and many other species of plants.


White powdery foliage disease on roses, deciduous azaleas, crabapple trees, euonymus.

Black Spot & Rust

Common leaf diseases of roses resulting poor plant health.


Often fatal root rot disease of oak and dogwood trees and many other plant species.

Verticillium Wilt

Wilt disease causing death of maple, redbud, and ash trees.


Wilt disease causing death of maple, redbud, and ash trees.

Poor Soil Conditions

Top soil removed, plants growing in heavy clay or subsoil, poor drainage. Results in poor root growth, decline in plant health and often death.

Poor Watering Practices

Either too much causing root rots or too little resulting in leaf burn, poor growth or death.

Improper Planting

Root systems planted too deep, major cause of plant decline and death.

Improper Pruning

Ttopping, over thinning, lion’s tailing, resulting in ugly plants hazardous trees and plant death.

Nutrient Deficiency

Foliage problems caused by poor soil and lack of nutrients.

The Solution

Collier Arbor Care’s plant health care program provides the most holistic and state of the art approach to tree and shrub health care available. This program cares for the entire plant from the root to shoots. Our customized program of regularly scheduled inspections enables us to diagnose and treat problems before they damage plants. We carefully select environmentally friendly materials when targeted treatments are necessary. After each inspection, we provide a report of our findings, treatments and recommendations. Fruit tree programs and optional treatments, such as fertilizing and pruning to promote vigorous healthy plants, are also available.