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Bee Notes
Linn County Master Gardeners
in conjunction with OSU Extension Service
What is happening with Mason Bees?
From Rich Little
This spring had unusual fluctuations in temperatures and rain. Many of us saw plants emerge and/or bloom at a different time from past years. That meant for mason bees, in some areas, their food sources (pollen & nectar) were not present in sufficient qualities to keep many of the bees alive much less help the female produce eggs for next season. A good example was my Big Leaf Maple, its bloom period occurred several weeks later than past years. This also occurred with some fruit trees.

From Bee Notes and bee friends we have heard a mix of how the mason bees are doing. Some sites have the mason bees filling holes quickly while others were seeing little or no activity. Those who are having success likely had yards/gardens that were producing enough pollen and nectar for the bees and available at the right time. This past April was one of the driest on record for many areas making it harder for the bees to find mud to line their nesting tubes. It was also a cold month further slowing plant growth.
Click on image for larger view
It is normal that the cocoons may not hatch right after you put them out. We do not know all the triggers that tell the bees when to wake up and emerge from their cocoon, but temperature is a major one. So cool days will influence this emergence. Depending on when you put out your cocoons in the emergence tubes, you may not see much activity until there are warmer temperatures and plant growth is sufficient to produce enough pollen and nectar that the female needs to stay alive and then start producing eggs. What I have seen at some of our breeding sites is that many bees are emerging but very few egg cells are being produced by the females compared to past years. I feel many of the bees are not finding enough food to keep them going. It is likely that the coming years will present a major challenge for us to recognize and respond to these changes that are occurring in our gardens/yards if we are to help our native pollinators maintain sustainable populations.

Cooler nights appear to have much less effect on emergence time. The bee can handle cold nights. It will likely be several weeks from the time a female starts producing eggs. She has to provision the egg cell with food, builds a mud wall sealing the egg in the hole and then repeats this process enough times to fill the tube at which time the female will plug the hole with the rough mud plug that you see. Take a walk around where you have the Mason Bee nesting blocks/tubes and make sure there is mud available for the bees. We have had much less than our average rain falls, as result there is not as much mud in some areas.
Click on image for larger view
Click on image for larger view
If you find any damage from woodpeckers or jays, try to prevent more damage as soon as possible. You can put a screen with about 1” openings around the box. Ideally the screen will be about 4-6 inches away from the holes. Woodpeckers will damage your block while enjoying the tasty cocoons. Jays seem to like to pull the tubes out. If tubes are dropped, the egg or larva can be displaced from the pollen ball.
Click on image for larger view
If you move your block or tubes when the mason bees are active, they often will abandon the nesting hole, so it is important to not move the blocks and/or tubes. You can add tubes or blocks if you do not move the existing ones.

When the female Mason Bee emerges from the hole that her mother laid the eggs in, she will fly around that hole while she starts to make a mental map of that area. We have found out most female bee show a strong preference to nest in the same area that her mother chose and from which she emerged.

This season I am doing an intensive survey of our breeding sites to see if there is a strong preference on the part of the Mason Bees for certain tube/block system and tube materials among other things. (We have 6 sites and are looking for more.)

Another observation I wanted to share from these sites is that one blocks was ‘active’ with numerous female bees filling the ‘holes’ with their off springs (98 holes plugged as of today), but another block just 35 feet away had very little female activity (4 holes plugged). Every year the bees try to teach me something and every year they do. I’m just not sure what they are trying to tell me this year.
We thank the almost 800 subscribers for being patient with us as we are busy and do not always put out as many Bee Notes as we plan to do. Thank you also for supporting mason bees!!

We have enjoyed answering questions and hearing about how the bees are doing. We encourage you to continue to ask questions.

Remember the next critical steps are taking your cocoons (blocks and tubes) in on June 1st to avoid parasitic wasp damage. The harvesting procedures you follow with your cocoons in mid-October/early-November will determine the survival rate of your bees for the following season. Follow our classes and best management practices with your bees and you could achieve a 90% survival rate.

Hope your year has been good so far for you and your bees.
Questions- let us know. (Contact links below)

Rich Little (and Ranee Webb)
Note: Our guidelines are tailored to the Willamette Valley of Oregon. We want blue orchard mason bee cocoons that you purchase from us to be used within the east to west boundaries of the Coastal Range to the Cascades. The northern boundary is the Portland/Columbia River areas and southern boundary is the Umpqua Valley area. Check with your county Extension agent if you live outside these areas.
As always, thank you for supporting bees!
Questions? Contact:
Ranee Webb - Email Ranee
Rich Little -  Email Rich
Link to Blue Orchard Mason Bee Calendar
Link to Leaf Cutter Bee Calendar
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Linn County Master Gardener Association · 33620 McFarland Rd · Albany, OR 97389 · USA

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