Pest shreds Solomon’s seal

Q: We have a nice bed of Solomon’s seal which flower well. But each year, the leaves are turned into lace curtains by small green caterpillars. Can you offer a cure that will break the life cycle of this pest?


A: The leaves are eaten by the larvae of the Solomon’s seal sawfly, Phymatocera aterrima. You’ll find the adults around your plants a flowering time. Related to bees and wasps, rather than flies, they are black with dark wings held along their body in the manner of moths, and longish antennae.
In May eggs are laid into the surface of the stems and hatch fairly quickly. The ‘caterpillars’ are pale grey and begin feeding on the undersides of the leaves.
When mature, the larvae fall to the ground where they pupate. They overwinter as pupae snuggled into the soil around crowns of the plants.
A heavy infestation looks horrible but the plants suffer very little, and flower just as well the following year as if the attack hadn’t happened. But Solomon’s seal is valued as a foliage plant right through to autumn, so it makes sense to bar this pest if possible.
The best method is to pinch off the baby grubs as soon as they hatch. Look under the leaves every few days after flowering. You could use a contact herbicide such as pyrethrum, but hand picking is a surer way.