Pests

Three major pests of the Mason bee are Houdini flies, mites & Chalcid wasps.

Houdini fly pest
Houdini fly

The Houdini fly is relatively new to North America. It prefers moist areas and thus is more prevalent in Coastal area. It sneaks into a Bee cavity and lays eggs on the pollen ball. The eggs hatch and consume the contents of the cell.

Phoretic Mite

Hairy-fingered or Krombeini mites multiply rapidly and consume the food supply in a cell. Infested cells will transfer mites to more bees the following year. They can be seen with a magnifying glass.

Chalcid Wasps

Using a long, stinger-like ovipositor, these wasps pierce cocoons through thin nesting materials then lay a series of eggs inside the larva. When hatched, they eat the larva and eventually escape the cocoon through a tiny hole.

Other pests can be a problems at times, especially Chalkbrood. Go to the SARS Website on Managing Alternative Pollinators and go to Appendix A at the bottom of the page.

Pests can be expected to give you problems every year, sometimes a little, sometimes a lot. You can’t control the weather but you can take steps to minimize the damage they do. Using the best nesting materials, cleaning practices, and manipulating the cocoons in a timely manner can greatly enhance the production of healthy cocoons and keep the environment friendly to the Bee.

Nest with a few good cocoons plus some cells with infestations of mites or Houdini fly larva. The mite cell is full of brown feces plus microscopic white mites numbering in the thousands.
Nine good cocoons plus 2 cells with pollen balls, where the bees egg failed to take hold. If mites are present the pollen balls may be consumed over the summer. Some cocoons are obscured by brown specks, which is larvae feces. This is normal and not harmful.
Brown parchment paper was rolled up and inserted into a round hole. Nine perfect cocoons are visible.