GALLSA gall is an abnormal development or out growth of plant tissue resulting from an irritation produced by bacteria, fungi, or insects. They take on many shapes, sizes and colors. Abnormal warts, swellings, and knots on leaves, twigs and branches of trees and shrubs are usually galls. Most galls on leaves are caused by small insects or insect-like pests such as wasps, midges and mites. These creatures attack leaves as they are forming in the spring. Gall tissue is essentially tissue created by the plant in response to the injury. Removing the leaf galls in most cases will cause holes in leaves.
The types of galls are too numerous to mention in one fact sheet. Also, the damage varies with the type of gall. The presence of galls does not indicate that the plant is likely to die. The damage caused is primarily aesthetic and localized to certain parts of the plant. Control is usually not warranted. However, occasionally, galls develop in such numbers that the leaves become distorted and loose their natural beauty, or may fall prematurely.
It is recommended to rake up and discard any gall infested leaves. Twig and branch galls can be pruned out and destroyed. Chemical recommendations for some specific galls are available upon correct identification.
Galls that occur on roots or stems of herbaceous material are caused by a soil-borne bacteria and called Crown Gall. These galls vary from pea size to several inches in diameter and give the appearance of a cancer-like growth. Plants with numerous or large crown galls may show reduced growth, yellow leaves or other symptoms of general distress. Severely infected plant material is more susceptible to winter injury. These galls disrupt the flow of water and nutrients between the roots and leaves. Death can occur.
Avoid wounding plants while transplanting, cultivating and mowing them. Clean pruning, budding, and grafting tools between cuts with fresh liquid household bleach. Carefully dig and dispose of severely infected plants. Do not replant the same type of plant in the spot for at least 5 years.
Commonly affected plants include Euonymus Wintercreeper, Roses, Privet, Rhododendrons and many nut plants.