White serpentine trails in the leaves of columbine are a sure sign columbine leaf miners are feeding in your plants.
These insects lay their eggs on the surface of the columbine leaves. The eggs hatch and a small worm-like insect enters the leaves. They feed between the upper and lower surfaces of the leaves leaving them intact. Their feeding causes the snakelike trails that are usually our first indication that these pests are present.
Fortunately their feeding is not harmful to the plant’s health, so treatment is not needed. Once inside most insecticides will not control these pests since they are safely munching away inside the leaves.
You can improve the plant’s appearance with a bit of pruning. Cut the plants back to the ground once they finish blooming. The new growth will be fresh and free of leaf miner damage for the remainder of the season. Plus, it prevents reseeding.
A bit more information: The columbine sawfly is an occasional pest of this perennial. These worm-like insects start feeding on the leaf edges in spring. Control small populations by removing and dropping them in a bucket of soapy water.
June 6, 2020
Ebert's Greenhouse Village
June 9, 2020
Milwaukee Public Library
Virtual Gardening Seminar
August 6, 2020
Ebert's Greenhouse Village's
Ladies Night Out