Sawflies are a group of insects in the suborder (Symphyta) of the Hymenoptera (bees, ants and wasps). There are about 500 species of

Sawfly are small winged insects, related to bees, wasps and ants. Their caterpillar-like larvae feed on the leaves or fruits of certain plants, including apples, gooseberries and Solomen’s seal.

Solomon's seal sawfly larvae feed in groups and defoliation can occur very quickly. Defoliation usually occurs after flowering and plants normally recover and grow in the following year. Polygonatum is also often defoliated by slugs and snails, a night time search will often reveal the culprits.

• 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

Whilst the defoliation caused by Solomon's seal sawfly can appear severe it normally occurs after flowering and the plants will usually put on healthy growth in the following year. Therefore this insect can be tolerated and the plants will survive.

Check susceptible plants frequently from late May onwards so action can be taken before a damaging population has developed. When choosing control options you can minimise harm to non-target animals by using the methods in the non-pesticide section below. Pesticide treatments are likely to kill natural enemies and are only likely to be successful if the entire plant can be reached.

Non-pesticide

• Where possible tolerate populations of sawfly, plants usually recover from defoliation
• Encourage predators and other natural enemies of sawfly in the garden, such as birds and ground beetles
• Check plants regularly from May onwards for the presence of larvae and remove by hand where practical

Pesticides

The RHS recommends that you don't use pesticides. Most pesticides (including organic types) reduce biodiversity, including natural enemies, impact soil health and have wider adverse environmental effects.

Where you cannot tolerate sawflies, manage them using the information above as your first course of action.
 
Pesticide treatments are likely to kill natural enemies and so reduce the likelihood of natural control and can lead to resurgence of the target animal.

If you do decide to use pesticides, the shorter persistence products (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife.
 
The pesticides listed are legally available in the UK. This information is provided to avoid misuse of legal products and the use of unauthorised and untested products, which potentially has more serious consequences for the environment and wildlife than when products are used legally.
 
Always follow the instructions on the products. For edible plants, make sure the food plant is listed on the label and follow instructions on maximum number of applications, spray interval and harvest interval.

Homemade products are not recommended as they are unregulated and usually untested.
Be aware that products such as Neem oil are not registered for use in the UK and we cannot advise on their use.

Plants in flower must not be sprayed due to the danger to bees and other pollinating insects.

• If numbers of larvae are too high for hand picking, control may be achieved by spraying with pesticides. Spraying at dusk is likely to be more effective

• Organic contact insecticides containing natural pyrethrum (e.g. Bug Clear Ultra 2, Neudorff Bug Free Bug and Larvae Killer) have a largely physical mode of action. These are broad spectrum so will kill a wide range of insects. Several applications of these short persistence products may be necessary to give good control. Plant oil and fatty acid products are less likely to affect larger insects such as ladybird adults

• Further information about the use of pesticides available for management of sawfly is available on the pesticides for gardeners leaflet

Inclusion of a pesticide product does not indicate a recommendation or endorsement by RHS Gardening Advice. It is a list of products currently available to the home gardener.

Download

Pesticides for gardeners (pdf document outlining pesticides available to home gardeners)

Adult Solomon’s seal sawfly are black-bodied insects, 8-9mm long, with two pairs of blackish grey wings. In appearance they are similar to medium sized flies but are in the same group of insects as the bees, ants and wasps, the Hymenoptera. 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.