E-56
ornamentals insects
CONTROLLING GALLS ON SHADE TREES AND SHRUGS
Donald L. Schuder, Extension Entomologist
Galls are abnormal growths on plants. They are caused by the feeding of living organisms,	including bacteria, 	fungi,nematodes, mites and insets. These organisms stimulate plant cells in such a way that the cells grow into galls, which serve as protection for the pests. There are hundreds of kinds of galls, each characteristic of the organism producing it. This	 publication deals only	 with galls on ornamentals that are caused by mites and 	insects. Although 	these	 mite
and insect-produced growths may disfigure twigs and foliage, they usually do not affect the health or vigor of the host plant. If the plant is unhealthy or dying, chances are that something else is causing the trouble.
Following is a discussion of five of the more common galls found on trees and shrubs in Indiana, and suggestions on how to prevent or control them. They are pictured on pages 2 and 3, along with many other galls that may infest ornamentals but are usually not prevalent enough to warrant control.

MAPLE BLADDER GALL
The silver or soft maple tree is often attacked by tiny mites that cause small, wart-like growths on the foliage. These growths are first red, then turn green and finally black. They occur singly or in clusters and may be so abundant that the leaves become crinkled, deformed and drop early. Once formed, the galls cannot be removed from the leaves because they are composed of plant tissue and are actually a part of the leaf.
Many homeowners become alarmed when they discover infestations of the maple bladder gall, fearing that their trees might die unless control measures are taken. This is not so, for the galls never cause permanent injury and actually have
little effect on tree health and vigor. The galls do, however, detract from the normal beauty of the foliage.
The maple bladder gall mites overwinter in cracks and crevices of the bark. As the buds swell in the early spring, they migrate out on the bud scales. When the buds open, the mites feed on the newly developing leaves. In response to this feeding, hollow galls are formed; the mites then live, feed and mate inside them. In the fall, the mites move back to the bark to hide over the winter.
Control. For control of the maple bladder gall mite, during the winter or in early spring just before the buds open, homeowners may either spray with dormant-strength lime-sulfur at 1 gallon of the liquid or 4 pounds of the dry form in 10 gallons of water, OR spray with a dormant superior oil spray as recommended on the label, OR use Kelthane 35% WP (wettable powder) at 1 pound. (Caution: lime-sulfur will discolor paint, stone and concrete, so be careful around buildings.)
Commercial certified applicators may use Guthion 2L at 1-1/2 to 2 pints or Guthion 2S at 1-1/2 to 2 pints or Metasystox R at 1 to 1 1/2 pints or Systox 2 at 1 to 1-1/2 pints or Baytex 4 at 2 pints per 100 gallons of water.
HACKBERRY LEAF GALLS
Most of the galls found on the leaves of hackberry are caused by jumping plant lice. In the late summer or fall, the small winged adults leave the galls and fly about seeking places to hibernate. In doing so, they may invade homes and become annoying household pests.
Control. To control the jumping plant lice That produce hackberry leaf gall, either hire a commercial firm to inject Bidrin, OR apply 1-1/2 to 2 pounds of Sevin (carbaryl) 80W or 2-1/2 quarts of
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA 47907