Green Industry Resources
Hort Update- Seasonal Information for the Green Industry
My roses have round sections chewed out of the leaves. What's causing this and will it damage my plants?
Perfectly round holes that appear as though they were made by a large paper punch are the work of leaf cutter bees. These small bees are one of the most important pollinators in the garden. Since the damage they do to plants, ranging from roses to oaks to hydrangeas, is mainly aesthetic, control or elimination of these insects is not recommended.
To make this perfect circle, the bees plant one foot as the center point, and rotate around it, cutting the leaf tissue. The don't eat the leaf sections, they use them to form the lining for their nests. The nests are usually built in hollow stems or canes and this activity can, on occasion, cause stem dieback on roses and other ornamentals. However, this damage is usually minimal compared to the positive presence of these bees for pollination. To prevent tunneling in rose canes, seal the pith after pruning cuts are made, using a drop of white glue.