Managing incubation must begin with planning the timing of bee hatch and their release.  When bees are released they must have immediate access to food, in the form of nectar, or they will leave the field in search of it and not return.  If bees are released too early, before there is sufficient bloom, many will be lost and both bee and seed yields will decline.  On the other hand, the earliest blooms produce the largest and greatest quantity of seed pods and are most likely to mature into seed before fall frost.  The later the bees are released into the fields, the more potential see yield will be lost.  The ideal time to release bees is when the field is in 40% - 50% bloom.  This is determined by picking random stems and calculating the percentage with at least one bloom. Correct timing is important!  

Attached is a Calendar of Leafcutter Bee Incubation

Download this file (Incubation Calendar.pdf)Incubation Calendar.pdf[ ]150 kB




 Introduction of formaldehyde fumigation (using paraformaldehyde product) for many producers in Manitoba is their first treatment choice for chalkbrood control, over bleach or heat treatments. Formaldehyde fumigation of live cells is conducted in the spring in conjunction with the incubation of the cells for development of adults and subsequent alfalfa pollination that season. While it is very effective at controlling leafcutting bee pathogens, there are health concerns with formaldehyde gas as it is toxic and overexposure may be fatal (EC/HC 1999). It may be harmful by inhalation, ingestion, or skin absorption. For these reasons it is important to avoid dangerous exposure to formaldehyde and to follow the product Handling Precautions as indicated on the label. 

The current formaldehyde-based chalkbrood control practice is to expose the leafcutting bee cells and equipment to high concentrations of formaldehyde gas for a 24-hour period, then ventilate the fumigation area for 48-72 hours, and longer if necessary. Neutralisation with ammonium bicarbonate quickly reduces formaldehyde concentrations in the air without adversely affecting chalkbrood control and without hurting development of the leafcutting bees (Lafreniere 2001). It is generally accepted that formaldehyde gas reacts with ammonia gas to produce hexamine (synonym hexamethylenetetramine) (and potentially other amine gases). While hexamine has been identified as a harmless substance (Kawamata and Kodera 2004; Ostermann 2005), other sources indicate that hexamine is an irritant to eyes, nose, and skin, is hazardous (Dugan and Serago 2005; NJDHSS 1999), and may decompose to formaldehyde in the presence of perspiration (ie sweat; slightly acidic 4-6.5) (Dugan and Serago 2005), and therefore should be handled with caution. In the solid form, hexamine is a white, crystalline powder with a mild ammonia odor.


This study assesses the levels of formaldehyde gas in the air that may be left behind following the fumigation of live leafcutting bee cells, neutralization with ammonia gas, and venting, at a local producer operation, and discusses the safety risk associated with residual substances.

See Attached Report