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Leafcutter Bees

| By | Pests

Leafcutter Bees (Megachile mendica)

GDD Window (base 50): First observations late spring – persisting throughout season​

Overview:

  • About the size of a honey bee but are mostly black with white bands on the abdomen
  • Females have a “pollen basket” of long hairs on their lower abdomen which they use to transport pollen
  • Solitary insects which construct nests in preexisting narrow cavities
  • Females construct their nests using foliage and flowers to make the half-inch long cells, cutting round pieces for the base and oval pieces for the walls, and lining them with petal fragments before filling them with pollen and nectar
  • Females lay eggs on the pollen mass and then cap the cell with foliage pieces
  • Females can control the sex of their offspring through withholding sperm from male eggs
    • Males develop faster, so females are often laid in the deeper cells and males closer to the entrance of the nest
  • Young bees chew their way through the nest after they hatch, first waiting for their siblings to emerge before them
  • Grubs are pale and legless, before molting into prepupa, spinning a silken cocoon that eventually turns dark brown before pupae emerge and then finally molt to become adults
  • The final eggs laid during the season will hatch and then overwinter within their cocoons, where warming temperatures will induce pupae to emerge
  • Host plants: Many different plants, including those with flowers for pollen and nectar, and plants with petals and leaves that are somewhat malleable for nest building (Red Bud (Cercis) is most commonly seen host plant in nurseries)​

Management:

Cultural Practices:
  • Natural predators: parasitoids, flies, wasps, and beetles, acrobat ants
  • Coelioxys is a leafcutting bee which lays their eggs in the nests of other leafcutter bees, and then these bees will eat the young of the bees originally in the nest
  • Avoid treatment when possible
    • They are superior pollinators to other bees, especially for apples and legumes (specifically alfalfa)
    • They have no nest guarding instinct and rarely sting
  • Cover susceptible plants with cheesecloth or loose netting to deter leafcutter bees
  • Cover pruned rose cane ends with thumb tacks, glue, or wax to prevent bees from tunneling
  • Fill holes in wood that could be used for nesting
  • Remove decaying wood where bees may nest​
Photo: Steven K. Rettke, RCE

 

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