Curled leaves are one of the most common types of damage to roses. A species of leaf wasp, the rose leafroller wasp, is responsible for this.
Small green larvae
The insect, which is only a few millimeters in size, usually hatches from the soil under the plant at the same time as the leaves emerge. The wasps lay their eggs in the undersides of fresh leaves. However, some leaves are only pierced on a trial basis and no egg is laid. The leaf responds to this stimulus by curling along the leaf vein. A small greenish larva is later found in most of the curled leaves.
The rose leafroller wasp flies from April to early June, depending on the weather. In early summer, the larvae migrate from the leaf coils to the upper soil layers, where they later pupate and overwinter. The sunnier, warmer, and windless the weather in spring, the more extensive the damage.
Pick off leaves and dispose of soil layer
Infested rolled leaves can be picked off and disposed of in the residual waste. Spraying with a pesticide is not particularly useful because the pests are well packed in the rolled leaves. However, if it comes to infestation of almost all the leaves, picking is hardly possible (because then your rose would be bare).
However, in the fall you can remove the soil from under your rose and apply new soil. This way you regulate the infestation for the next year enormously. In spring you can carefully rake the surface and apply compost or fertilizer. This will further strengthen the roses against pests and diseases.
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