Pests and Diseases Viewer

The larval stage of Solomon’s Seal Sawfly Phymatocera aterrima can completely defoliate Polygonatum species and hybrids by early summer. These slow moving, grey, caterpillar-like larvae seems to suddenly appear from early June to July. During this time they will eat the foliage of Solomon's seal from the top down.
Adult Solomon’s Seal Sawfly are black-bodied flies, similar to house flies, 8-9mm long, with two pairs of blackish grey clear wings. They emerge about the time the Solomon Seal is coming into flower.
Female sawflies, like all sawflies, have a sharp, saw-like ovipositor or egg-laying appendage which is used to place their eggs inside the leaf stem. This causes vertical purplish brown scars, up to 2cm long, to develop where the eggs were inserted.
Most adult sawflies feed largely on the grains of pollen and on algae and therefore do not damage the Solomon Seal directly.
The eggs hatch and it is the greyish white caterpillar-like larvae with black heads that does the damage. They are up to 2cm long. The larvae look like caterpillars but differ by having at least 6 pairs of prolegs where as true caterpillars have a maximum of 5 pairs. They feed in large groups, usually under the leaves, so damage can occur very quickly. Initially they make small elongate holes but by mid-summer, the stems may be stripped of foliage.
The fully fed larvae drops into the soil where they overwinter and pupate in the following spring to start the cycle again.
Defoliated plants will survive and produce new shoots in the following year. Repeated attacks will weaken the plant and allow other pathogens to flourish and eventually kill the plant.
Picture by James Lindsey's Ecology of Commanster Site from Wikimedia Commons.
See these other Sawflies Apple, Aquilegia, Geranium, Geum, Goosberry, Iris, Large Rose, Plum, Rose Leaf-rolling, Sawflies.

Control

Remove the larvae from the underside of damaged leaves.
Spray with systemic insecticide when the leaves are about to open.
Encourage birds and other predatory insects into the garden.