Deformed Lilac Leaves Maybe a Sign of Problems

Q. My lilac bush had some leaves on it that suddenly look like they are deformed. What is the problem?

A. Deformed or crinkled leaves can indicate several things. If the edges of the leaves were damaged, scorched, the interior of the leaf will continue to grow while the dead margin will not. This can cause leaf deformity called cupping.

Stink bug

Feeding damage by some bugs on leaf buds before they open can cause crinkled or deformed leaves. These include the stink bug group of insects such as the leaf footed plant bugs. Look for bugs on the
bottom of the leaves or crawling on stems.

Leaf deformity can be caused by “weed killer” sprays that drifted on the foliage during windy or hot weather. Some herbicides, like dandelion killers for lawns, cause leaf deformity if it comes in contact with leaves as they are enlarging or expanding.

Squash bugs, one of the stink bug types

Bottom line, most likely the damage is temporary and as more leaves develop they should be normal. However, if you inspect the plant and see these types of insects apply an insecticide for ornamental plants and spray leaves and stems during early morning hours. Spray the undersides of leaves because this is where most the bugs hang out.

Make sure the plant gets enough water. This is a plant that likes compost and wood mulch, not rock mulch. Lilacs do not like rocks covering the surface of the soil. Every year apply 1/2 cubic foot of compost on top of the mulch and water it in. Use a high phosphorus fertilizer that promotes flowering of woody plants.