Leaf Rolling Sawfly damage is easy to see. The leaf rollers literally roll up the leaves - often on rose bushes - and lay their egg inside the cosy little nest they have formed. The egg hatches out into a grey green grub - caterpillar - that feeds on the sap from within its home.
The rolled up leaf normally shrivels and dies.
Damage starts in late spring, as leaves at the tips of new growth are drawn down to form a circular 'enclosure' for the eggs to be laid and resulting grubs to feed on the leaves and sap.
In this process, the rose sawfly emits a chemical secretion which forces the leaf to curl.
Contact insecticides are not normally effective, for the do not easily penetrate the damage rose leaves. Systemic insecticide such as Provado Ultimate Bug Killer will normally work, but it will have to be applied at an early stage to be really effective. Perhaps Provado used as a part of a regular routing spraying of special rose bushes may be the best form of defence.
The adult sawfly is similar to a wasp in appearance, and similar to the group of hover wasps, hover flies that are beneficial in the garden.