Reasons for Low Bee Reproduction

Why Didn't the tubes fill up?

All of the solitary bees we sell are tunnel nesting bees. This means that they emerge from cocoons in the spring (blue orchard mason bees,californica beesandtexana bees) or summer (alfalfa leafcutter beesandsunflower bees), and then spend the rest of their lives filling up tubes with their offspring. They do this by selecting a tube, collecting pollen (food source for baby), laying an egg, and then sealing off the egg and pollen in a cell and repeating. The bees spend their entire lives harvesting pollen and reproducing.

At the end of the season it seems logical to assume there should be more bee cocoons to harvest than were released.  Usually this is what happens and everybody is happy. Unfortunately, this scenario isn’t always the case. Our goal is to help your garden, fruit trees and bees thrive. If you know what went wrong it can be corrected for next season. Let’s talk about some possible reasons the bees didn’t reproduce as hoped.


 The number one reason we see for bees not filling the tubes with offspring is the use of pesticides during the growing season. All pesticides can harm the bees. If pesticides were used that is probably the reason for low numbers.

Solution: Try using organic gardening techniques to control unwanted garden pests. If the need to spray is overwhelming spray at night while the bees are sleeping in the house. Cover the house while spray is drying but be sure to remove the cover before sunrise. Try to focus spray away from blossoms so the bees will have as little contact with it as possible.

Moving the bee house:

Solitary bees have an exact way of knowing where their tube is. If you move the house after they have emerged it may cause the bees to find a new home elsewhere. The safest times to move the house are prior to emergence in April/May and in June before the summer time bees emerge but after the spring time bees are done.

Solution: Avoid moving the bee house.

Not enough empty tubes:

We recommend having at least one empty tunnel per bee cocoon released. If bees are bought in tubes we recommend _______ empty tubes. If there aren’t enough tubes for the females to lay their eggs in they will leave to find a new nesting area.

Solution:Provide enough nesting material for the bees. Inspect the bee house periodically throughout the growing season. If you notice there aren’t very many empty tubes available it’s time to add some more. If the house is full you can set up another bee house close to the original and the bees will begin filling the new house.

Not a good enough pollen source:

Bees will not lay eggs without putting pollen (baby bee food) in first. If the pollen is unavailable it will reduce reproduction. Monocultures (growing all one type of crop) shorten the window for bees to reproduce because all the blossoms are available at the same time and then stop. This is why we suggest planting a variety of flowering plants. There is new research we are aware of (to be blogged about in December when the final reports come out) that suggests mason bees aren’t able to reproduce as well in almond orchards.  The pollen is not as available on almond trees. The almond growers are still happy with the pollination the mason bees do for their orchard but they haven’t been able to grow their bee numbers like they expected to.

Solution: Plant a variety of flowering plants. If growing monoculture crops try planting wild flowers in the buffer zones and dead spaces. This will ensure pollen is available for the bees lifespan; extending the reproducing window of your bees.

Not enough sun:

Bees are cold blooded and need the sun to warm them up to get out pollinating. When bees aren’t exposed to morning sun they are slower and less productive pollinators. Who can blame them though it would be like you without your caffeine for the day.

Solution: Place the house facing between South and East. Make sure the house is getting good exposure to sunlight.  Move the house (prior to emergence) if the house is in an area that is shady all day.


It won’t make a difference how productive the bees are if they are being eaten. Keep an eye out for the signs of predators. Some signs include: tubes on the ground or out of bee house, animal/bird  prints or fecies in the area of the bee house, ant hills and ant trails near the bee house etc..

Solution: Check out ourpest postto find out how to manage pests.

Late freeze or premature emergence: 

After the bees emerge from their winter hibernation a hard freeze spells death. This can’t always be avoided, since we can’t control the weather. (We really should have figured that one out by now, don’t you think?)

Solution: What we can do is keep the bees in the fridge to control when they emerge. Keeping them in the fridge until the chance of frost is low and their are buds starting on the trees will reduce the risk of the bees freezing before they can pollinate and reproduce.

Lacking clay:

 Mason bees require clay to form cells between their eggs and to cap off the tubes. If they aren’t able to find a suitable material the bees may fly off to find new nesting areas.

Solution: Provide clay for the bees. You can find some locally or just get some of ourshere.

Environmental factors:

This one requires some detective work to figure out as each environment is unique. Here are some ideas to get you thinking. Do your sprinklers hit the bee house at night? Did you recently paint or stain in the area of the bee house (some scents may deter bees from nesting)? Are there bright lights shining into the tubes at night? Is the house secure or does it move around a lot in windy conditions?

Solution: The solution will be as unique as the problem. Generally the bees are happy as long as their basic needs are being met but we have seen times when the location of the house did not promote bee activity.

Raising native pollinators is fun and easy. When there’s bee trouble there is always a reason why. Now that you’ve discovered the trouble make the proper adjustments and watch your bee population take off.

Remember it is our goal to help you succeed raising solitary bees. If you have any further questions or concerns we are happy to help! Contact us by email at or by phone:801- 648- 9035