Leafcutter bee nesting holes should be left intact over the winter.

The spring is the best time to harvest leafcutter cocoons and harvesting leafcutter bee cocoons will reduce chalkbrood disease and Pteromalus, a very small parasitic wasp. Adult leafcutter bees will emerge from the harvested cocoons and because they were allowed to emerge from loose cocoons they will not spread chalkbrood to their nesting materials. Leafcutter bees need the warmth of summer to develop into adult bees and this step is called incubation.

Leafcutter bees love warmer weather and fly best at and above 75F. If you wish to get ready for leafcutter bees now, set up your bee house with morning sun and afternoon shade. Place your leafcutter bee nesting materials with 6mm nesting holes into the bee house. Apply our InvitaBee Spray for leafcutter bees when you are ready to set out your cocoons. Place out your incubated leafcutter cocoons once you see adult bees emerging.

Harvesting Leafcutter Bee Cocoons

Harvesting leafcutter bee cocoons is very simple. For reusable wood trays, unstrap and remove one tray from the stack at a time. For natural reeds, pinch the open end and the reed will start to split (there are no cocoons at the open or capped end). Using a Philips head screwdriver or popsicle stick, gently remove cocoons from each groove of the reed or wood tray. For cardboard BeeTubes, nick the open end and unravel the tube. Leafcutter cocoons are not waterproof and can not be washed and this is why you stored leafcutter nesting trays in your cold garage over the winter.

Leafcutter cocoons inside a reusable wood nesting tray

Leafcutter cocoons will sometimes stick to each other, forming a line of cocoons. The cocoon colors will vary from yellow, green, and brown and some are made from petals. Place the leafcutter cocoons into a BeeGuard Bag, cinch the top closed and store in an unheated garage or shed.

Because leafcutter bee nesting materials were left out all summer, your chances of finding a wild bee or beneficial hole-nesting wasp are higher. If you can, close your reusable wood tray or natural reed and allow wild bees and beneficial wasps to develop. If you must, place wild cocoons or larvae into their own LeafGuardian Bag and check for development using our blog tips for watching the development of wild cocoons and larvae

For reusable wood trays, brush any remaining debris out with a dry brush. Bees don't mind the look of a dirty nesting tray and we want the scent of previous nesting bees to remain.

Leafcutter Bee Cocoon Incubation

Leafcutter bees spend the winter as larvae and they need time to develop into adult bees. The warming temperatures of early summer cue the cocoons to start developing. We call this stage of their life cycle incubation and you can time incubation to match your summer garden blooms.

Development time depends on how much time they are in warmer temperatures.
• At consistent 84°F (30°C), adults emerge after 20 days
• At 70°F (21°C), adults emerge after about 42 days

Spend a few moments now to plan ahead for the open flowers of your garden. If you can, try putting your BeeGuard Bag near your hot water heater and remember to check periodically.

We recommend that you also place a Bee Defender parasite glue trap, completely assembled, into the bag during incubation. Pteromalus parasitic wasps emerge before the leafcutter bees do and the Bee Defender will help reduce this common pest. Use the green lure in the Bee Defender to attract Pteromalus, check for the gnat-sized parasitic wasp after about 7-12 days of incubation.

Some leafcutter bees have a shorter development cycle and may begin emerging after 18-20 days of warmth. Remember to check on your incubating cocoons. Release emerged adult bees and place the remaining unopened cocoons into the bee house.

Intact cocoons can't regulate their temperature above 90°F (32°C), place them in a cooler location (inside your cool house) and release adult bees as they emerge until the hot weather passes.