Rose Sawfly
Overview:
Rose Sawfly larvae can rapidly defoliate rose foliage, and the stems might scar as a result of egg laying.
The two species of rose sawfly have yellow abdomens with black heads, legs and thorax.
One type rolls the leaves, and the other eats the leaves to expose the veins.
Leaf Rolling sawfly symptoms can be seen when the leaves curl downwards along their length to form tightly rolled tubes.
This curling is caused by chemicals secreted by the female sawflies when they insert eggs into the young leaves.
A week later the eggs hatch and the pale green caterpillar-like sawfly larvae begin to eat the leaves from the inside.
Later, when fully fed the larvae move into the soil to over winter in readiness to pupate the following Spring.
Systemic insecticides, may give some control over the larvae, similarly some general insecticides may kill off the adult flies but there is nothing available to kill the eggs other than the removal of the affected leaves.
The Rose Sawfly will produce at least two generations from May to October, by laying their eggs on soft rose shoots.
The eggs hatch into pale green larvae with black spots and yellow blotches.
The larvae grow up to 25mm (1 “) long and feed in groups and strip the leaves back to the veins.
When fully fed, they pupate in the soil.
There are a number of suitable insecticides to control them, but sometimes the best method is to lift the larvae off by hand.