Gooseberry sawfly

What is common gooseberry sawfly?

Damage  is caused by the caterpillar-like larvae of a sawfly pest that devour the leaves.

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1

The foliage on gooseberry bushes is often striped by gooseberry sawfly.

Symptoms

• Severe defoliation of the bushes can be caused by the caterpillar-like larvae, which are up to 20mm (almost ¾in) long
• The larvae are pale green, with many black spots, and they have black heads
• The adult 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
• The larvae of other sawfly species and moths may also eat the foliage of gooseberries and currants

Control

Non-chemical control

• Regularly check the plants from mid-April onwards for sawfly larvae and pick them off by hand
• A pathogenic nematode, sold as Nemasys Grow Your Own, can be watered onto infested plants. The nematodes enter the bodies of the sawfly larvae and infect them with a bacterial disease

Chemical control

• Spray when young larvae are seen, with an insecticide approved for use on gooseberryand red currants
• Suitable insecticides are thiacloprid (Provado Ultimate Bug Killer Ready To Use or Concentrate), lambda cyhalothrin (Westland Plant Rescue Fruit & Vegetable Bug Killer), or an organic pesticide such as pyrethrum (Py Garden Insect Killer, Scotts Bug Clear Gun for Fruit & Veg, or Doff All in One Bug Spray)

Download

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

Biology

• The common gooseberry sawfly is the most troublesome pest of gooseberries. 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