Common Gooseberry Sawfly
On Crops: Gooseberry, red currants and white currants
Throughout UK and Europe (temperate regions only)
This is the most common pest of gooseberries, white and red currants. Adult sawfly are yellow with black markings and black heads. The adult females usually lay their eggs into the undersides of lower leaves. These hatch into pale green, black-spotted and black-headed larvae that feed gregariously and rapidly devour the leaves. When mature (20mm in length), the larvae form silk cocoons in the soil and pupate within. Up to three generations can occur each year. The final generation overwinter as pupae in the soil.
Sawfly larvae cause severe damage to bushes by devouring the leaves. Often complete defoliation will occur, leading to loss of fruit set.
Prune bushes so that they have an open structure which allows good airflow. Sawfly prefer to lay their eggs into dense bushes. Bushes can also be covered with a horticultural fleece as they are self-pollinating.
Check bushes regularly for leaf damage and remove any larvae that can be found. Where the infestations are severe, as a last resort organic Pyrethrum-based products are available from garden suppliers. These will need to be applied following the label instructions.
During the winter months, dig around the base of bushes to expose the overwintering pupae to insectivorous birds and other predators.