Eric Mader, Pollinator Outreach Coordinator, the Xerces Society for Invertebrate Conservation
Leafcutter and mason bees share many of the same enemies. Their parasites and diseases appear with regularity in many operations and can significantly reduce bee numbers unless controlled. The severity of these problems depends upon individual management practices, region, and contamination levels of initial bee stock. Problems can also vary significantly from year to year, even within isolated operations.
Unfortunately, while particular management practices may reduce one problem, they may eventually promote others. For example, loose-cell management facilitates annual nest block cleaning and can significantly reduce chalkbrood contamination. However, unless properly secured, loose bee cells are easily attacked by parasitic wasps.
Sanitation and regular monitoring are essential to maintaining bee health. Fortunately with vigilance, most bee parasites and diseases can be maintained at acceptably low levels. While the following section describes individual parasites and diseases as well as methods for their control, readers should see Appendix G for a more comprehensive approach to maintaining bee health.