Among the things you don’t expect to see on your rose leaves: round, perfect holes cut out of the edges, as if a tiny jigsaw had been there.
If you see these holes, you’re seeing the work of leafcutter bees. They prefer rose, Virginia creeper, green ash, and lilac leaves. Leafcutter bees look like honey bees, and they’re important pollinators, but these native North American bees are not aggressive and have only a mild sting.
Female leafcutter bees cut the leaf pieces and take them back to the nest (built in the ground, thick stems, or rotting wood) to build cells for eggs. She puts a mixture of nectar and pollen and one egg into each leaf piece and then closes it. Young bees emerge from the cells the following season.
Damage
Leafcutter bee holes usually don’t hurt the plant, so the damage is only aesthetic. Leafcutter bees may nest in large rose canes, but here as well there’s typically little damage, as they tend to tunnel only in the pith (the center of the stem).
Control
Pesticides are fairly ineffective on leafcutter bees. To prevent the bees from cutting into leaves, cover their favorite plants with cheesecloth or other netting. You can also try to destroy nesting sites. But remember, leafcutters are valuable pollinators, and they do only minor damage, so you’re doing your garden a favor by letting them be.
—photo courtesy of the Kemper Center for Home Gardening at the Missouri Botanical Garden.