Homes of mason bees

Homes of mason bees (Photo credit: Wikipedia)

By October, mason bees have finished pupating inside their cocoons and are mature, waiting for springs’ signal to emerge.

Between now and early December, you can handle the bees inside their cocoons without damaging them, or waking them up accidentally, making this the ideal time to clean your mason bees and blocks and prepare them for winter.

It is important to keep naturally occurring mites and parasitic wasps to a minimum to maintain the health of your bee population.

The following are specific spring management techniques to prevent mites from establishing in your bees if you live in the Pacific Northwest or other long cool spring locations:

  • Gently remove cocoons from the stacking trays. Trays should be cleaned with a mild (5%) bleach solution. Cocoons can also be carefully washed in a mild bleach solution to remove mites and maintain a healthy population. For complete instructions refer to “Pollination with Mason Bees” (#S426).
  • If you are using the block and straw system, carefully remove the bee filled straws from the block. New clean straws can then be inserted in the block. The book “Pollination with Mason Bees” has instructions on removing the cocoons from the straws if your bees are infested with mites and need to be cleaned.
  • If you are using home-drilled blocks without straws it is best to make new blocks each year and not re-use older ones. It will not be possible to remove the cocoons without damaging them, or remove mites and other debris. Place your new block where the filled one was and store the filled block outside or in a refrigerator as described below. Late January, or when your fruit tree flowers appear ready, position the filled block a few feet lower and below the new block. When your bees emerge in the spring they will use the new block.

Storing your bees outdoors

Mason bees overwinter outdoors and survive temporary periods of below-freezing weather in the Pacific Northwest. Store the bees (loose cocoons or straws) in a mouse-proof container with small breathing holes until late January. Loose cocoons or straws should be cushioned on several layers of soft paper inside a cardboard box inside the mouse-proof container. Keep the container in a dry location.

Bee-filled wood blocks will benefit from being stored in a mouse-proof container also. Then in late January you can put the blocks out, or the cocoons out in the release box, and they will become active as outdoor temperatures warm; or you can put them in the refrigerator and manage the time of their emergence.

If your environment is more extreme, the bees may not survive the winter outdoors. You will need to store them in the refrigerator, as described below, once winter settles in.

Storing your bees in a refrigerator

English: Orchard mason bee on apple bloom

Mason bee on apple bloom (Photo credit: Wikipedia)

If you need to protect your mason bees from severe winter weather, or you want to manage when your bees emerge in the spring, to coincide with blooms in your orchard, you need to keep them in the refrigerator at 36-39° F.

Put the bees in the refrigerator late September or early October, or just after cleaning and drying the cocoons, for the most reliable results. It is important to maintain proper humidity for the bees if you store them in a frost-free refrigerator.

Put the cardboard box of cocoons or filled wood block inside a plastic bag that you put several small holes in, along with a barely moist paper towel. Close the bag, and put it in the refrigerator.

Mason bees will be eager to emerge from their cocoons by mid-February, earlier if you waited to put them in the refrigerator until January. Look for hints regarding releasing your bees in the February Growing Tips, or the book “Pollination with Mason Bees” (#S426).

View our Bees and Bee Supplies page to order bees, nest blocks, or books.

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