Galls are swollen areas on trees, usually the leaf, caused by insects. The most common insect culprit is the aphid. These little pests are annoying. They do not do permanent damage, or kill the trees they attack. However, the effects of galls are unsightly and sometimes disfiguring. Galls cause bent limbs, leaf disintegration, and stem dieback. Getting rid of galls requires an attack on the cause of the problem: aphids.
Galls usually host more than one insect invader. They also house bacteria and mites. Inside each gall a unique ecosystem develops with communities of pests in hiding. Getting rid of galls requires consideration to all types of problem pests.
Galls Stay Put
Once a tree has a gall it stays put. There is no way to get rid of a gall. Therefore, the best method of curing galls is preventing them.
Insecticides and miticides designed to kill on contact are best for aphids and other gall creating insects. Aphids hang out on the undersides of leaves and getting spray on insecticides to that area is difficult.
Spray soil at the base of the tree with insecticide in early winter. Aphids hibernate in the dead leaf mounds around the base of trees. Spraying the area with insecticides shows good results in keeping aphids at bay in the summer months. Repeat the application in early spring right before buds appear for extra protection.
Insects to Fight Insects
Lacewings and ladybugs are great predatory insects that destroy aphid populations. Introduce them to your yard, or garden in early spring and they will feed off the young aphids.
Always follow the directions on the label of insecticide products. Impatience and desire to get rid of galls can tempt you to apply more than the product allows. It is illegal to use pesticides in a way that contradicts the instructions on its label.