There are many good reasons to harvest the leafcutter bee cocoons you raised last summer.

You will reduce pests like grain moths, earwigs, and the parasitic wasp named pteromalus, take inventory of your leafcutter bee cocoons, clean your nesting trays, and control the development of your bees (also known as incubation). Harvesting leafcutter cocoons can help you time their activity for when your summer garden begins to bloom.

If you're also raising mason bees, a good reminder to harvest leafcutter cocoons is to do it when you're setting out your mason bee cocoons. The best time to harvest your leafcutter cocoons is in the early spring before your daytime temperatures warm above 60F, at this temp the bees can slowly start to develop. Depending on your incubation method, it can take 4-6 weeks for your leafcutter bees to develop into adults. So, another guideline for when to harvest leafcutter cocoons is 4-6 weeks before your summer garden blooms.

Harvesting leafcutter cocoons is really similar to harvesting mason bee cocoons, the difference will be in what you see and where you store your leafcutter cocoons.

Open reed for harvesting leafcutter bee cocoons

Harvest Supplies:

• Filled 6mm Wood Nesting Trays, 6mm Natural Reeds, or 6mm paper BeeTubes

• A tool like a dull pencil, a Philips-head screwdriver, or a Popsicle stick

• A tray or cookie sheet for catching cocoons and debris

• An old toothbrush or stiff wire brush

• An empty CocoonGuard Bag (your first set of leafcutter cocoons arrived in a similar bag)

• A BeeGuard Bag for incubation

• A Bee Defender parasitic wasp glue trap

To begin, simply remove the green rubberbands and protective cardboard backing from your 6mm reusable nesting trays. Gently pry apart the trays one tray at a time. For 6mm Natural Reeds, pinch the open end (there are no cocoons at this end) and a split will form - slowly split and crack the reed apart. For 6mm paper BeeTubes, use a pair of scissors to snip the open end and tear the paper tube along the spiral. Leafcutter bee cocoons are not waterproof and cannot be soaked - do not soak 6mm BeeTubes to remove leafcutter bee cocoons.

For Natural Reeds you can make a gauge stick to help you decide to open any partially filled reeds.

Use your preferred cocoon removal tool to gently release the cocoons from the nesting material. It can be easier to remove cocoons from the interior end of the nesting tray or natural reed - the back of each cocoon is rounded.

Use an old toothbrush or a stiff wire brush to remove leafy capped ends, grain moths and their cocoons, and other debris from your reusable wood trays.

Place your harvested leafcutter bee cocoons into an empty CocoonGuard Bag and leave the top open. Assemble a Bee Defender glue trap and add one green lure for leafcutter bee pests. Parasitic wasps will develop and emerge while leafcutter bees are developing and they will be attracted to the glue trap instead of the leafcutter cocoons. Place the filled and open CocoonGuard Bag and assembled Bee Defender into your BeeGuard Bag. The BeeGuard Bag provides a safe space for any emerged adult bees.

Leafcutter bee cocoons ready for incubation

Next, you have a choice of where to place your harvested bee cocoons. If your summer garden will bloom later, you can place the BeeGuard bag in your unheated garage or shed - always keep bee cocoons out of direct sunlight.

If you wish to start incubating your leafcutter bees right away, place the cocoons in a warm location like in your water heater room.

Development time depends on time spent in warm temperatures:

• At 84°F/30°C, adults emerge after 20 days
• At 70°F/21°C, adults emerge after about 42 days
• Some native leafcutter bees have shorter development cycles
• After about 7-12 days begin checking for Pteromalus and kill these very small parasitic wasps

Periodically check on the development of your leafcutter bee cocoons and place the CocoonGuard Bag in your bee house when you see adult bees begin to emerge.