Something is eating the leaves on the roses – if left to it, stem-like leaf veins would be all that remain. Seeing the ragged foliage and looking more closely, I see around the leaf edges tiny creatures that resemble caterpillars. They are not caterpillars, though, they are rose sawfly larvae.
There are two common species of rose sawfly in the UK, Arge pagana and Arge ochropus, with A. pagana being the most common. As to how they got there, the adult fly, which looks a bit like a brown flying ant, will have laid her eggs in tiny cuts that she made in the leaf, using her saw-like ovipositor (egg-laying organ). The roses that have been affected so far are all young containerised plants - a patio rose, ‘Sweet Dream’, climbing ‘Iceberg’ and ‘Zephirine Drouhin’, as well as some small unknown plants coming on from cuttings, one of which may or may not be ‘New Dawn’.
They are all lovely young roses and I don’t want to see them damaged so, as there are plenty of wild roses in this area, I have been checking all the plants daily, removing those leaves with sawfly larvae on them and putting them in the bin. Roses that are already in the ground, which are larger and more robust, I shall leave for the birds to clean up.
Sawfly larvae are curious little things. The slightest disturbance of the plant causes them to curl their bodies so their ‘tails’ are pointing away from the leaf. I can only guess that this must be a defence mechanism designed to put off predators, maybe with a ‘Eeww, I’m not eating that’ response. Such methods don’t work very well on humans and I’ll be nipping off the leaves of the young containerised plants as soon as I see them being chewed.
More about sawflies:
A general sawfly page from the BBC
Pictures and information from Bugs and Weeds