Last updated on January 22nd, 2021
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Roses are among the most popular plants for commercial and residential gardens. They bring with them the arrival of spring and maintain stunning flowering displays with energizing aromas all year round. But what happens when the leaves start to curl, taking away from that otherwise beautiful display?
Curling leaves on a rose bush are indicative of a serious pest issue called rose leaf-rolling sawfly.
Rose leaf-rolling sawfly
Don’t be fooled by discussions of weedkiller damage. The rose leaf-rolling sawfly is a much more likely culprit. Sawflies have caterpillar-like larvae which feed on your plants until they become adults. The adults have wings and take on the appearance of flies even though they are in the same family as bees and wasps.
These insects cause a lot of damage and not just to roses, they are even own to strip Gooseberries of all their foliage overnight. Firstly, the females lay their eggs into the leaflets and secrete chemicals during the process which cause the leaves the roll. There are times no egg is laid but the leaflet still gets probed which results in the same curling.
Out of these eggs emerge larvae much like caterpillars which then feed inside of those rolled leaves.
What are the symptoms?
So, how can you tell when you really do have a problem with a rose leaf-rolling sawfly?
The leaf margins will begin to curl downward and inward along the length of the leaves until they roll up completely into a tube. This will take place between April and June, and it happens within 24 hours of the egg being laid.
You will notice pale green larvae inside the rolled leaves if you unfurl them, and the rolled leaves will remain curled throughout the summer.
How can I treat rose leaf-rolling sawfly?
If you notice the symptoms of rose leaf-rolling sawfly, you can a) do nothing for a light infestation or b) use pesticide or non-pesticide controls.
Light infestations are something most rose bushes can manage, with a small amount of foliage affected. But anything larger should be treated appropriately.
Non-pesticide controls mean picking off the affected leaves as soon as you notice them, preventing the larvae from eating and maturing. However, removing a large number of leaves from your rose bush can be more harmful to its overall health than the comparative damage a maturing sawfly would do.
Alternatively, you can use pesticides but they might not be incredibly effective, as they won’t prevent the female sawfly from laying eggs and won’t impact the larvae already inside the rolled leaves.
That said, vigilance and removal here and there of affected leaves can go a long way toward overall control and maintenance of a healthy rose bush.