Harvesting Leafcutter Bee Cocoons
Harvesting leafcutter bee cocoons is a quick and easy way to ensure a healthier leafcutter bee population!
But, if that wasn't enough, harvesting also allows you to:
- Take Inventory of your leafcutter bee population; and,
- Share your extra leafcutter bee cocoons (and knowledge) with local friends and neighbors.
We know this can be a little intimidating for first-timers, so we've created a simple guide with video tutorials to help you along the way. You'll learn the importance of harvesting cocoons, the best harvesting practices for our three different types of nesting materials (natural reeds, wood trays, and cardboard tubes), and how to store your leafcutter bee cocoons for healthy summer bees!
Why it is Important to Harvest Leafcutter Bee Cocoons
Productive bee nests are a buffet of food resources for pests and parasites, and the proximity of managed bees to each other allows diseases to spread quickly. We've repeatedly heard from researchers and bee raisers alike that the most effective control method of Chalkbrood and parasitic wasps is to harvest your leafcutter bee cocoons in the spring!
As bee raisers, it's our responsibility to provide these pollinators with healthy habitats to forage and nest. So, if you install an artificial bee house, then you'll need to take the time to harvest if you want to see healthy future generations of bees in your yard. Fortunately, it's a quick and easy process!
Steps to Harvest Leafcutter Bee Cocoons
WHEN: Start in early spring when dandelions begin to bloom. Allow your leafcutter bee cocoons time to develop into adult bees: they may need about six weeks of incubation to be ready for your summer garden to bloom.
WHAT YOU'LL NEED: Before you begin, you'll want to set up your harvesting workspace and gather your harvesting tools.
A quick note: harvesting can be a bit messy! We suggest laying down a layer of newspaper or an old sheet to make cleaning up easier and not wearing your favorite clothes.
So, what makes harvesting messy? Well, you'll find all sorts of things inside the nesting materials. As expected, you'll find healthy leafcutter bee cocoons, leaf bits, and leafcutter bee frass (poop). However, you may also find Chalkbrood, pollen mites (or other parasites), pollen loaves from bee eggs that never hatched, and possibly even dead leafcutter bee larvae. The combination makes harvesting a fascinating but messy process.
Don't be discouraged if you find any of these "problems" inside your nesting materials. We assure you, parasites and diseases are quite common! Many parasites are native predators that evolved alongside leafcutter bees. But that doesn't mean we have to allow them to feast on our developing bees!
Harvesting significantly reduces the incidences of pests, parasites, and diseases and allows managed bees to thrive year after year!
HARVESTING TOOLS: Fortunately, most of the tools we use for harvesting leafcutter bee cocoons are everyday items you likely already have!
- A Cocoon Comb for removing cocoons (for wood trays and natural reeds) - If you don't have a cocoon comb, you can use a Phillips head screwdriver, but harvesting will take longer since you can only remove cocoons one chamber at a time;
- BeeGuard Bag or CocoonGuard Bag or another breathable, transparent bag for leafcutter bee incubation;
- A stiff wire brush or old toothbrush to remove stuck-on debris (for wood trays); and
- Scissors to open nesting materials (for Cardboard BeeTubes).
Pro Tip: Some of your Natural Reeds or BeeTubes may have been partially filled with cocoons! Before opening, use a gauge stick to check if the materials are partially used or if they can be set aside for next year. Mark the stick at the length of the nesting tube and insert the stick into the open end of the nesting tube. If you can see the mark, there is a nesting chamber inside. If not, the reed or tube is empty, and you can set it aside for use next spring!
Step 1: Open Nesting Materials and Remove Cocoons
1. Remove the green rubber bands and the cardboard backing (save both to reassemble the trays).
2. Lift the first tray, and using the Cocoon Comb, gently remove cocoons, leaf bits, and other debris. Keep your removal tool at a 45-degree angle (see image below).
3. Remember to check both sides of the nesting trays for cocoons.
4. Brush away any pollen and leafcutter bee frass with a stiff brush or old toothbrush.
5. Gently clean wood trays with an old toothbrush dipped in a bleach and water solution (Ratio: 1 Tbsp. Bleach to 1 Cup Water) to remove any chalkbrood that may be present. Allow wood trays to dry thoroughly.
6. Once clean and dry, reassemble the nesting trays by aligning the side grooves. Double-check the trays are snug, and there are no gaps between the tracks.
7. Store with cardboard backing and rubber bands attached to trays.
1. Pinch the leaf-capped end between your fingers, and the reed will start to split. Don't worry; there won't be a cocoon at the open end of the reed. If you have a lot of reeds to open, you'll save your fingers by using a pair of pliers to pinch the leaf-capped end!
2. Pry the reed apart and use a Cocoon Comb to remove the cocoons gently.
3. Once all the cocoons have been removed, you can throw the opened reeds into the yard waste or compost bin!
Tear or carefully snip with scissors one end of the BeeTube, and it will easily unravel. Gently use your fingers to separate leafcutter bee cocoons from the paper.
Step 2: Store Cocoons
Unlike mason bee cocoons, leafcutter bee cocoons are NOT waterproof. Do not wash leafcutter bee cocoons!
Place cocoons in a BeeGuard or CocoonGuard bag or similar transparent, breathable bag and store them in your garage or shed until it’s time to incubate. We recommend that you lightly break leafcutter cocoons apart from the line of cocoons to allow bees to emerge from their cocoons without having to walk through diseased cocoons.
Step 3: Incubate Leafcutter Bee Cocoons
Leafcutter bees hibernate as dormant, mature larvae inside their leafy cocoons. The development time from larvae to adults is temperature-dependent. The warmer the temps, the faster bees develop into adults. We call this process incubation.
Plan to time your leafcutter bee emergence with your summer weather and open blooms.
To incubate, place your bag full of harvested cocoons in a dark, warm location, like an unconditioned garage, water heater room, or protected outdoor area.
Development of leafcutter bees is temperature-dependent. The warmer the temps, the faster bees develop into adults:
- At 84°F/30°C, adults emerge after about 20 days.
- At 70°F/21°C, adults emerge after about 42 days.
Pro Tip: Intact cocoons can’t regulate their temperatures above 90°F/32°C, if your storage area gets above 90°F/32°C during the incubation period, bring the cocoons to a cooler location, like indoors and release adult bees (in the early morning) as they emerge until the weather cools.
Your bee house may have attracted some native leafcutter bees last season. Some native species of leafcutter bees have shorter development cycles and will emerge early, so it's a good idea to check the bag periodically. Release any early emergers near your bee house.
Once adult leafcutter bees start to emerge, you can release cocoons by placing leafcutter bee cocoons into a cocoon hatchery or similar container and placing the container in your bee house.
Important: Pteromalus parasitic wasps (see image below) emerge after about 9-14 days and attack developing leafcutter cocoons. Remember to check periodically for any parasitic wasps. Kill any parasitic wasps you find in the bag.
Pro Tip: To ensure your yard and garden has enough leaves for the female leafcutter bees to build their leafy cocoons - plant peas, beans, or strawberries around the same time you start incubating leafcutter cocoons.
If you find yourself with extra leafcutter bee cocoons, you can share them (and knowledge) with local friends and family!