I have gotten several phone calls about leaf notches on redbud trees. This characteristic damage is caused by leaf cutter bees in the genus Megachile. Leafcutters in Megachile
and other genera are solitary bees that nest in hollow grass stems or other pithy stems they can easily excavate. They will also make nests in existing holes in wood but do not bore their own holes in wood (those are carpenter bees). Adult leaf cutter bees can be about as big as honey bees. They cut out round pieces of leaves to line their nests and pack in between brood cells. Damage by leaf cutter bees is general insignificant. In this area they seen to prefer
redbuds but will cut other plants including maples and roses. I have never seen more than a few leaves damaged on any particular tree and the damage is not enough to affect tree growth or health. Leafcutter bees are important pollinators of many native plant species and fruit and vegetable crops. In many urban and rural areas the plant species bees use for nesting have become less common than they used to be. Thus, bees cannot find suitable reedy grasses of tree holes to nest in. You can help conserve leaf cutters and other bees species by creating nest tubes. These are fairly simple contraptions that just require tying together bundles of reeds or drilling holes in blocks of wood to replace the nest substrate that used to be provided by plants. Visit April Hamblin’s other recent blog post for details. April is conducting research on how urbanization and urban warming affect bee communities, individual survival, and nesting. Visit her guest blog on yourwildlife.com or project description for details of her work.
Overall leafcutter bees are far more beneficial than harmful (they also rarely sting unless handled). My suggestion is to tolerate the subtle damage these bees cause and use it to teach other people about bees. If you are growing plants for sale you may not be able to do this but I rarely see leaf cutting on nursery stock.
MS student April Hamblin contributed to this post.