Over the past couple years, I have noticed the same two things happen to my columbine foliage each spring. After the plants reach peak bloom, the leaves start to get curvy, light brown lines though them. Shortly thereafter, all the foliage is gone, seemingly overnight—bare stems are all that remains. The plants bloom well each spring and the foliage is healthy before the problems occur. Should I be doing anything about this?
Columbine is one of the loveliest plants for the partial shade garden. Its susceptibility to columbine leaf miners is one of the few disappointing aspects of this perennial. This annoying little critter that likes to decorate columbine leaves with its winding, whimsical and white trails belongs to the family of leaf-mining flies. The pale brown adult fly lays its eggs on the underside of the leaves where the eggs hatch and the larvae that emerge penetrate the leaf and live between the upper and lower surfaces of the leaf. They feed on the inner leaf tissue, creating winding trails usually light green, light brown or white in color. The infested leaves may turn white and die.
Spraying the infested plant with a systemic insecticide is the best solution to the problem. Orthene or Cygon are two Ortho brand products that will work well for the elimination of these pests. You may also use these products as a preventative measure by applying the insecticides to the foliage before it is infested. As with all insecticides, follow the directions on the package carefully. It is also recommended to remove and destroy any infested leaves. Also, be sure to rake out and destroy any foliage remains in the fall.
The “here today – gone tomorrow” mystery surrounding columbine foliage is a problem entirely separate from the designing leaf miners. Foliage stripped off in one day leaving nothing but a columbine skeleton can be blamed on chewing caterpillars. These tiny, green, munching machines attack plants in late spring and early summer, just as your columbine is coming into full glory! Columbine’s beloved delicate and thin leaves are the perfect texture for their insatiable appetites. Usually flowers and stems are the only remnants left standing, bobbing in the wind.
All is not lost, however, as the foliage will grow back in the same season and the plant will certainly return year after year since the root system is not affected by the caterpillars. Protecting the new growth, before or after a caterpillar attack, is the key. As with the control of the leaf miners, Orthene or Cygon are your best bet to get rid of the caterpillars. Apply early in the season before these pests can do any damage, usually the end of May.