This is a leaf from my lilac tree. Many, but not all its leaves are like this...

Asked June 14, 2020, 3:54 PM EDT

This is a leaf from my lilac tree. Many, but not all its leaves are like this and it didn’t flower the last two years. Any idea what the cause would be? It gets full sun and is about 4 years old. It has no powdery mildew or black spots. I have never seen any bugs on it. I’m trying figure out if this is caused by a disease or an insect. I sprayed with Bayer Advanced Rose and Flower Concentrate about a week ago. It’s supposed to also help flowering trees with disease and insect control. Hoping this helps whatever this is. Feedback appreciated.

Waseca County Minnesota

6 Responses

It looks like galls. Could you send the picture of the underside of an infected leaf?

It appears that the yellow areas are bumps is that the case?

It is bumps on the leave. I’ve attached some additional pictures but do not have the original leaf in the picture sent. They are raised bumps. There are also bumps on the stems. As you can see from the picture there are various stages of leaf deformation. Some with holes, some with crinkled edges and raised bumps. The worst areas seem to be at the very tips of the branches.

This is the back side of the leaves in the last picture of my previous response. .

Here are a few more pictures of the tree. Not all leaves are like the pictures above. The bump is raised and doesn’t have a growth you could pick off of it. You can see the branches also have bumps on them. I’m not sure if that’s normal.

Last picture didn’t post

IT looks to be an infestation of scale.https://extension.umn.edu/yard-and-garden-insects/scale-insects.

It is too late to use a contact pesticide like insecticidal soap.
Your option is to use imidacloprid which is a
neonic, but the lilacs have flowered so there is no threat to pollinators.