Caterpillars On Roses - Dealing With Rose Sawfly

Last updated on April 5th, 2022

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Roses are very popular plants to have in any garden and are often scented. So much effort goes into maintaining them, such as spraying with fungicides in spring, undertaking the correct pruning methods and general care.

But what happens when you notice caterpillars on your roses?

For starters, these caterpillars are often the larvae of a common pest: the rose sawfly.

What are rose sawflies?

They are called sawflies because they take on the appearance of flies when they reach adulthood, however, they are actually in the same group as wasps, ants and bees. The larvae are like caterpillars and they grow inside the leaves of your rose bush, these often start to curl, eating their way to maturity.

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The large rose sawflies are pale in colour, with spots of black, yellow, and green. As they eat the leaves on your rose bush, they can cause serious defoliation.

Once they reach adulthood, they change colour, taking on a yellow abdomen with a black head and thorax.

How do you identify sawfly larvae?

You can tell when the issue really isn’t caterpillars and is actually the sawfly from a handful of symptoms.

The females lay their eggs inside the young, soft stems of the rose bush which then split open. So if you see elongated scars along the stems, it is indicative of the large rose sawfly.
The laying of the eggs and subsequent eating of your rose bush causes the leaves to curl, so if you see them curling inwards and downwards, it might be a sign. Moreover, the chemicals left behind by the females that cause this curling, maintain the curled shape while the young larvae subsist inside the leaves.
The caterpillar-like pests will appear with black and yellow spots and begin defoliating your rose bush during the summer.

How can you control it?

If you have a problem with sawflies, you have a few options. Firstly, you can leave the plant alone because a mild infestation won’t actually harm the overall health of your rose bush.

Secondly, you can handle larger infestations by removing the larvae by hand. If you see the tell-tale signs of eggs in the stems, you can remove those stems before the eggs mature.

Thirdly, larger infestations can be handled with pesticides. You can spray pesticides at dusk to kill off a serious pest problem. If you use pesticides, always follow the instructions on the label. You might need to apply them several times, especially if you are using organic insecticides with natural pyrethins instead of those with deltamethrin, cypermethrin, and cyhalothrin.