Key Features
- Discolored leaves
- Snake like pattern of discolor
- Stunted growth
Symptoms
Leaves become discolored as maggots tunnel through the upper and lower leaf surfaces. Leaf mines often start in a snake-like pattern. In heavy infestations, almost all available leaf surfaces can be mined. This can cause leaves to drop and stunt growth.
Biology
Several species of leaf-mining flies emerge from their overwintering stage in the spring to lay eggs in new leaves. Columbine leaf miners are among the most common species. Eggs hatch to maggots that tunnel under the leaf surface. Eggs take about a month to produce new adults that can attack. There are several generations per year. Other species of leaf miners present in other host plants have a similar life cycle.
Management Recommendations
Apply systemic insecticides to the leaves when injury is detected. Use insecticides like spinosad that penetrate the leaf to kill the maggots beneath. The new growth will be free of leafminers. Repeat the application if new mines appear. Other products directed to control adult flies are less effective in the home garden due to the almost continuous movement of adults into the garden. You can hand remove damaged leaves to improve plant appearance or wait until damaged leaves will fall off by themselves. Hand removing infested leaves may not be practical when almost all the leaves are mined.
Effective Pesticides
Active Ingredients include: Abamectin, Bifenthrin, Lambda- cyhalothrin, Permethrin, Spinosad
Resources
