Key to Common Insect Pest Problems on Leaves of Woody Ornamentals


What does the leaf damage look like?

No sign of distinct holes or chewing damage answer: Continue...

Distinct signs of chewing damage or holes of some type answer: Continue...


No sign of chewing damage


Leaves cupped, wilted, wrinkled, sticky, have many fine white to yellow spots or a scorched appearance.

These signs may be caused by any of a variety of sucking insects such as aphids, leafhoppers, plant bugs, scales, or mites.

Soft-bodied insects in distinct clusters or colonies on new leaves;
large volumes of a sticky honeydew waste that can give leaves a shiny appearance or result in growth of dark sooty mold
answer: APHIDS

Small, elongate insects that jump, move quickly or fly when disturbed. They cause fine white spots on leaves as they feed. Common on redbud in late summer. answer: LEAFHOPPERS

Are common on the lower surface of sycamore and azalea in mid- to late summer. They give leaves a bleached look and leave tarry black waste spots. answer: LACE BUGS

Flattened, oval insects. They can distort leaves of honeylocust or produce a series of small brown spots on leaves.

Distorted leaf growth

answer: PLANT BUGS

Found on trees and woody ornamentals. Some are flat and blend in with the bark, others are very distinct. Unlike galls, scales can be scraped off leaves or bark. Heavy infestations can cause twig dieback.
May produce large volumes of a sticky honeydew waste that can give leaves a shiny appearance or result in growth of dark sooty mold

Scales on tree branch


Feed on the lower surface of leaves giving the leaves a bleached look. Mites are very small and easy to overlook.

Fine spotting on leaf

answer: MITES

Maple leaves with partial petioles on ground answer: MAPLE PETIOLE BORER

Warts, bumps, or fuzzy patches on leaves, petioles or twigs that cannot be removed without tearing plant tissue. may be caused by tiny wasps, flies, or mites

Galls along leaf vein

answer: GALLS

Pale or dark blotches on leaf; winding trails or blisters; larva may be present

Leafminer damage



Chewing damage or holes present

Leaves look ragged or chewed; large sections of leaf material missing answer: Continue...

Pairs of holes equidistant from a major vein – in early spring answer: FROST BUD INJURY

Leaves chewed only on one surface but no complete holes answer: Continue...

Leaves held together with silk answer: Continue...


Large sections of leaves missing

Entire leaves chewed away or holes in leaves; larger veins may be intact; leaf material removed in a methodical way

Chewed leaf

Chewed leaf with main veins left

answer: Common leaf feeders:
BEETLES such as Japanese beetles, May beetles, leaf beetles, or chafers
CATERPILLARS, INCHWORMS or HORNWORMS - worm-like larvae with 4 or fewer pairs of fleshy legs on middle of body
SAWFLIES- worm-like larvae with more than 5 pairs of fleshy legs
LEAF BEETLE LARVAE- worm-like but without fleshy legs
BAGWORMS or CASEBEARERS - worm-like larvae in silken bags or cases; pieces of leaves may be attached

Leaves ragged and torn, usually without distinct holes or with random chunks missing answer: WIND DAMAGE


Leaves chewed on only one surface

Leaves chewed only on one surface but no complete holes; small veins and one leaf surface intact (small caterpillars or slug-like leaf skeletonizers)

Skeletonized leaf damage

answer: Early feeding by most small caterpillars begins as skeletonization
OAK SLUG SAWFLY LARVAE feed on the upper surface of oak leaves
PEAR SLUG SAWFLIES feed on the lower surface of pear, cherry and plum.
ROSESLUG SAWFLIES feed on the lower surface of roses.
ELM LEAF BEETLE LARVAE are dark colored and feed on the lower surface of elms.


Leaves held together with silk

Groups of leaves webbed together with or covered with silk answer: WEBWORMS or TENT CATERPILLARS

Individual or adjacent leaves rolled, creased or folded, may be held together with silk

Folded and rolled leaves




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