Sawflies are a group of insects 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.

Roses are also food plants for a range of other sawflies such as the rose leaf-rolling sawfly and rose slug sawfly or slugworm.

You may see the following symptoms:

• The female sawflies lay eggs in soft young rose stems, they can sometimes be found with their orange rear ends inserted in the stems. The stems often split open where the eggs were laid, resulting in elongate scars
• Whitish green, caterpillar-like larvae with black spots and yellow blotches can cause defoliation in early and late summer

Healthy roses can cope with some defoliation and the presence of some larvae can be tolerated.

Check roses frequently from spring onwards so action can be taken before a damaging population has developed. When choosing management options you can minimise harm to non-target animals by starting with the methods in the non-pesticide control section and avoiding pesticides. Within pesticides the shorter persistence products (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife than those with longer persistence and/or systemic action. 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 often recover from defoliation and roses are a food plant for several sawfly species
• Encourage predators and other natural enemies of sawfly in the garden, such as birds and ground beetles.
• Check plants regularly from May for the presence egg laying females, egg scars and larvae. Eggs within the scars can be destroyed by running a fingernail (or equivalent) down the scar. Larvae can be removed 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 than those with longer persistence and/or systemic action.
 
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) are available and broad spectrum so will kill a wide range of insects
• More persistent contact-action insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Resolva Bug Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer, Provanto Sprayday Greenfly Killer) and cypermethrin (e.g. Py Bug Killer). These products have long lasting action against insects including those that are beneficial
• Pesticides, with both systemic (absorbed and transported through plant tissues) and contact action, are available. These include  Flupyradifurone (Provanto Smart Bug Killer) for  use on ornamentals and selected edibles and the neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra). These pesticides are widely considered to be the most environmentally damaging, remain active for a long time and will kill beneficial invertebrates

Download

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

In Britain there are two species of large rose sawfly: Arge pagana and A. ochropus. The adult insects of both species have yellow abdomens with the legs, thorax and heads being mostly black. Arge pagana is the more common species. 

Rows of eggs are inserted into soft young rose shoots and female sawflies are sometimes seen dangling from such stems, attached only by their saw-like egg-laying organs.

After hatching, the larvae feed together in groups. They are pale green with black spots and yellow blotches, and are up to 25mm (about 1in) long. When fully fed, they go into the soil to pupate.

The large rose sawfly (Arge pagana) will produce two (sometimes three) generations from May to October. Arge ochropus usually has a single generation in early summer, but sometimes there is a second generation in late summer.

A guide to distinguish the adults and larvae of the two species of large rose sawflies can be found on the Sawflies of Britain and Ireland website, under information on Arge ochropus. One simple way to determine the species is that the eggs of A. ochrops are laid in a single row in the twig scar, A. pagana lays eggs in a double row.