Leafcutter Bees
Article and Images: Rachel Nilson, Plant Pathologist/Entomologist
Imperial County Agricultural Commissioner’s Office
Seasonally, leafcutter bees can attract a lot of attention. The occasional circular notching on landscape
plants can rapidly multiply giving many homeowners a good scare. Fortunately, the damage is shortlived and rarely does any permanent damage to typical landscape plants. For those homeowners who
live closer to agricultural areas, the damage will be much more significant than for those that live well
within city limits.
Leafcutter bees (Megachile sp) have in recent years become more widely used as pollinators for
agricultural crops. They are an important tool for farmers in a time where Colony Collapse Disorder and
Africanized Honey Bees threaten the population of honey bees nationwide. In addition, they do not
sting, so they pose less of a hazard to farmers, their staff, and the public.
There are many species of leaf cutting bees, but generally they are slightly smaller and appear slightly
grayish in comparison to a common honey bee. You may not catch the bees in the act, but the damage
is quite distinct. Notches of leaf or flower tissue will be removed in nearly perfect circles, just off of the
edge of the leaf. I often describe it as if someone used a hole-puncher on the leaves.
The damage that they cause is usually limited to plants with tender leaves, but may include newly
emerged leaves of a variety of plants with tougher leaves. I have seen newly emerged leaves of a plant
that were completely defoliated by leafcutter bees, while the older leaves were untouched. The most
commonly attacked plants in Imperial County include ash, bougainvillea, peppers, petunia, roses,
rosewood trees, tecoma (yellow bells), vitex, and vinca.
Insecticides do not provide effective controls of leafcutter bees in the landscape. The only proven
method of protecting your landscape plants is exclusion. This is accomplished by netting your plants
with material similar to cheesecloth. If you are going to attempt this, you should avoid using heavier
garden cloth in dark colors because with high summer temperatures the plants may be scalded. While it
is probably impossible to protect your entire garden, prized plants or plants that are sustaining the most
damage should be protected.
Fortunately, the bees are usually only present in the fields from June to early September. Most plants
that sustain damages are able to recover quickly. However, careful attention should be paid to ensure
that the damages don’t exceed what the plant can handle.
Figure 1: Leaf Damage on Vitex
Figure 2: Leafcutter Bee on Vitex
Figure 3: Leafcutter Bee on Vitex
Figure 4: Leafcutter Bee trailers in alfalfa seed field.