What is gooseberry sawfly?

Sawflies are in the same group of insects as bees, ants and wasps (the Hymenoptera). They have caterpillar like larvae that feed on plants the adults are winged insects that can appear fly-like. 

There are three common species of sawfly that can be found feeding  lon the leaves of gooseberry and some related fruit bushes.

Symptoms

• Defoliation of the bushes can be caused by the caterpillar-like larvae of one of three species of sawfly
• Larvae of the common gooseberry sawfly are up to 20mm (almost ¾in) long, pale green, with many black spots, and black heads  The adults are winged insects;  females are 5-7mm (up to ¼in) long and are yellow with black heads and black markings on the thorax; males are similar but more extensively marked with black, including the upper surface of the abdomen
• Larvae of the pale spotted gooseberry sawfly are slightly smaller than those of the common gooseberry sawfly and have pale green heads. It has one generation a year with larvae present in May and June 
• The small gooseberry sawfly can have up to four generations of pale green larvae from late April onwards
• The larvae of some moths may also eat the foliage of gooseberries and currants
• Plants will usually survive complete defoliation, however this may reduce yield

Control

Check susceptible plants frequently from spring onwards so action can be taken before a damaging infestation has developed. When choosing control options you can minimise harm to non-target animals by starting with the methods in the non-pesticide control section. If this is not sufficient to reduce the damage to acceptable levels then you may choose to use pesticides. Within this group the shorter persistence pesticides (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.

Non-pesticide control

• Where possible tolerate populations of sawfly
• Encourage predators and other natural enemies of sawfly in the garden, such as birds and ground beetles.
• Check plants regularly from April for the presence of larvae and remove by hand where practical
• A biological control (pathogenic nematode), sold as Fruit and Vegetable Protection, can be watered onto infested plants. The nematodes enter the bodies of the sawfly larvae and infect them with a bacterial disease. This nematode is available from some garden centres or via mail order. The nematode should be applied during cool damp weather

• If numbers of larvae are too high for hand picking, control may be achieved by spraying with pesticides. Spraying at dusk is likely to give the best results
• Organic contact insecticides containing natural pyrethrins (e.g. Bug Clear Gun for Fruit & Veg, Neudorff Bug Free Bug and Larvae Killer). Several applications of these short persistence products may be necessary to give good control
• More persistent contact insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer, Provanto Sprayday Greenfly Killer) and cypermethrin (e.g. Py Bug Killer)

Downloads

Pesticides for gardeners (pdf document outlining pesticides available to home gardeners)Non-pesticide control

Biological control suppliers (pdf document)

Biology

• The common gooseberry sawfly is the most frequently found of the gooseberry sawflies. It can have three generations a year, with the larvae active in late April to June, July, and August to September
• The female sawflies lay eggs on the underside of leaves, low down in the centre of the bush, so the young larvae go unnoticed until they have eaten their way upwards and outwards, devouring the leaves as they go
• Defoliated plants are weakened and may produce a poor crop the following year
• When the larvae are fully fed, they go into the soil, where they spin silk cocoons and pupate
• The pale spotted gooseberry sawfly only has one generation a year with larvae present in May and June
• The small gooseberry sawfly has up to four generations a year with larvae present from late April