E-29
DEPARTMENT OF ENTOMOLOGY
ornamental insects

SCALE INSECTS ON SHADE TREES AND SHRUBS
David L. Matthew, Jr. and Timothy J. Gibb, Extension Entomologists
Scale insects are common pests of shade trees and shrubs. More than 60 different kinds have been found in Indiana. Yet they are often overlooked or ignored until tree or shrub branches "mysteriously" start to die.
Mature scales usually are found firmly attached to branches or foliage of woody plants and never move. They kill their host by sucking the sap; at the same time, they give off a sweet "honeydew," which attracts ants and flies. A fungus often grows on this honeydew when it drips off onto the lower leaves, giving those leaves a sooty appearance.

Young scales are called crawlers. They look like mites and wander about over the plant before settling down and becoming permanently attached to the bark.
The scale insects most prevalent in Indiana (and plants affected) are listed below. These plus additional ones are illustrated on pages 2 and 3. Control measures are described in Tables 2 and 3 on page 4.

CONTROL MEASURES
Scale insects can be controlled either with a DORMANT SPRAY, applied just before growth begins in the spring and when temperatures get above 45°, OR with a SUMMER-SPRAY, applied when the young crawlers are actively moving about over the plant. No matter which schedule you follow, thorough coverage is essential and high pressure desirable, especially on evergreens.

TABLE 1. COMMON SCALE INSECTS IN INDIANA.
Kind and Description of Scale	Plants Seriously Affected
COTTONY MAPLE SCALE: Large scales attached to the undersides of branches. In spring, when depositing eggs, the scales resemble strings of popcorn. The crawlers are found on the undersides of branches.	Soft maple, box-elder and linden. Others affected.
OYSTER SHELL SCALE: Small, grey or brown scales about 1/8 inch long and curved like miniature oyster shells. May completely encrust the branches.	Lilac, elms, soft maple, ash, popular, dogwood, linden, willow, redbud, privet, hemlock.
EUROPEAN ELM SCALE: Oval-shaped, reddish-brown scales about 1/4 inch long surrounded by a white waxy fringe.	Elms of all ages.
SCURFY SCALE: Small, dirty-white, pear-shaped scales not over 1/10 inch long. They lie very flat on the bark.	Most serious on young elms, apple, willow and dogwood.
SAN JOSE SCALE: Tiny, grey, circular scales about the size of a pinhead and having a yellow center nipple. May completely encrust the branches.	Apple, crabs, quince, mountain ash, flowering cherry, other trees & shrubs.
TERRAPIN AND LECANIUM SCALES: Large, brown, hemispherical scales that look like miniature turtles.	Tulip, hickory, magnolia, oak and some evergreens.
PINE NEEDLE SCALE: Small, elongated, white scales attached to the needles of evergreens.	Pines, fir, and spruce of several species.
JUNIPER SCALE: Tiny, circular, greyish-white scales with a yellow center. Found on foliage and hard to see.	Juniper and arborvitae.
EUONYMUS SCALE: Elongated, brownish-grey scales and small, elongated, white male scales found under foliage and on twigs.	Euonymous, pachysandra and bittersweet.

PURDUE UNIVERSITY COOPERATIVE EXTENSION SERVICE • WEST LAFAYETTE, IN 47907