Galls: what has the nerve to grow on my tree leaves?

. Today, we found galls on an Elm tree. While the exact insect or mite of this particular gall is unknown, there are over 1500 mites and insects that cause these abnormal growths, we wanted to take the time and give you some insight on what to do if your plants should come down with this ailment. Usually, no harm will come to your plant, your plant will just look unsightly; but sometimes galls can actually kill the plant. That normally happens when the growths occur on woody stems. If the leaves are affected, the plant will recover. Some common causes are insects or mites feeding on the plant or responses to infections, fungi, bacteria or viruses. Leaf galls appear as twisting and curling of leaves, but they are able to carry out photosynthesis.
Gall growths occur when there is a reaction from a chemical stimuli between the pest organism and the plant’s hormones. The cells within the plant are directed to increase rapidly and form a hard outer structure that provides food and shelter for the larvae that live inside. In order to correctly identify your plant’s invader, it needs to be examined under a microscope to determine the species. The unique color, shape and structure of the call is characteristic of each gall.
Some control methods are to trim out the affected parts and to destroy fallen leaves in the fall as these provide overwintering habitats. If the plant is not in a prominent place in the yard you can simply leave it be. If the plant’s long-term health is in jeopardy seek out identification of the pest at your local Extension Office.

Joyce Browning Horticulturist, Master Gardener Coordinator
Video credit: Bethany Evans Longwood Gardens Professional Gardener Program Alumni; CPH

The University of Maryland Extension Home and Garden Information Center's mission is to develop and deliver science-based, sustainable gardening information and solutions through outreach education for better human and environmental health.

[melodyivey]

I've never seen these before until today on a Hackberry tree

[littlebeebs]

I’m concerned they will make it inside to my prized succulents. I have over 300 succulents indoors. Brevipalpus mites have already made it inside to really damage my succulents. I don’t want these guys on them too. I have some Abacide 2 injections. Is it too late to inject now ? The leaves are matured now on the trees and they’ve grown their helicopters ( seed that helicopter to the ground in fall ).