Leafcutter bees usually attack rose canes, but they do sometimes take the leaves of other flowering plants to line their nests. Cover your plants with loose netting (cheescloth will do) during periods when leafcutter bees are most active. Do you have rotting boards or thick-trunked plants nearby, and do you see sawdust poking out of holes or tunnels? That's where they live. Eliminate such detritus from around your yard. There really is no effective pesticide you can use.