Solomon's seal sawfly

The larval stage of Solomon’s seal sawfly can completely defoliate Polygonatum species and hybrids in early summer.

Solomon's seal sawfly

Quick facts

Common name Solomon’s seal sawfly
Latin name Phymatocera aterrima
Plants affected Solomon’s seal, Polygonatum species and hybrids
Main symptoms The foliage is eaten by whitish grey caterpillar-like larvae
Caused by Larvae of a sawfly
Timing May-July

What is Solomon's seal sawfly?

This pest is a caterpillar-like insect that eats the leaves of Solomon’s seal plants.

Symptoms

Sawfly caterpillars feed in large groups so damage can occur very quickly. Keep vigilant for early signs;

  • Greyish white caterpillar-like larvae with black heads and up to 2cm (¾in) long seen on the underside of the leaves, eating elongate strips out of the foliage
  • Complete defoliation may occur
  • Purplish brown scars, up to 2cm (¾in) long, may be seen on the leaf stems where eggs were inserted

Control

Non chemical

Search for the larvae and remove them from the underside of damaged leaves.

Chemical

Spray infested plants with  deltamethrin (e.g. Bayer Sprayday Greenfly Killer), lambda-cyhalothrin (Westland Resolva Bug Killer) or pyrethrum (e.g. Py Spray Garden Insect Killer, Bug Clear Gun for Fruit and Veg) while the larvae are still small.

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Biology

Adult Solomon’s seal sawfly are black-bodied insects, 8-9mm long, with two pairs of blackish grey wings. They emerge in late spring at about the time when their host plant is coming into flower.

The female uses her saw-like eggs-laying organ to insert rows of eggs into the leaf stems. This causes vertical purplish brown scars to develop where the eggs were inserted.

The larvae feed together in small groups on the underside of the leaves. Initially they make small elongate holes but as the larvae increase in size, their appetite also increases. By mid-summer, the stems may have been stripped of foliage.

The fully fed larvae go into the soil where they overwinter and pupate in the following spring. Defoliated plants will survive but may produce reduced growth in the following year.

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