Tree Pests & Insects: What to Look For

Look at the pattern, not just the insect.

Note which tree is affected, whether the problem is on new growth or older leaves, and whether it is limited to one branch or spread across the canopy. Take close photographs of the damage and a wider view of the tree.

Not every insect on a tree is a pest. Some feed on other insects, and visible damage can also relate to water, roots, disease or growing conditions. Identification helps avoid unnecessary treatment.

Small insects on tender growth.

Aphids often gather on young shoots or the undersides of leaves. Their feeding may be associated with curled or distorted growth. They can leave sticky honeydew, sometimes followed by dark sooty mold.

Photograph the insects and affected leaves before anything is washed or treated. The presence of beneficial insects can also help inform the next step.

Small bumps on leaves, twigs or bark.

Scale insects can be easy to mistake for part of the plant. Depending on the species, they may appear as small raised patches or waxy coverings. Heavy infestations can be associated with yellowing leaves, leaf drop or declining growth.

Some scale insects produce honeydew; others do not. Identification matters because different groups have different life cycles and management needs.

Holes and damaged wood need a closer look.

Some insect larvae feed within stems or wood. Small entry or exit holes, fine wood-like debris or local dieback may warrant a closer inspection, but those signs alone do not identify the insect or the extent of damage.

“Beetle” describes a broad group, including beneficial insects such as lady beetles. Avoid assuming that every beetle you see is harming the tree, or that a spray will resolve damage inside the wood.

Check the undersides of leaves.

Tiny white adults may lift off when foliage is disturbed. Eggs and immature whiteflies can be found on leaf undersides. Like aphids and some scales, whiteflies may leave honeydew that supports sooty mold.

Record which plants are affected and how widespread the symptoms are. A close photograph of the underside of a leaf is often more useful than a photograph of flying adults alone.

Identify the cause, then choose a response.

Share your observations with an arborist if damage is spreading, branches are declining or you cannot identify what is happening. A plant health care assessment considers the tree’s overall condition as well as visible pests.

Treatment should match the identified problem and its severity. The appropriate response may involve monitoring, changes in care or a targeted treatment; it should also account for beneficial insects.

Learn more about our approach to feeding and treating trees.