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May 20, 2021

This isn’t Rich. Thanks for the use of your
photo, anonymous subscriber!

Ranee and I have enjoyed your questions and hearing how the bees are doing. We encourage you to continue to ask questions and Rich will continue to answer as many as he can.

Remember, the next critical step is taking your cocoons (blocks and tubes) in on June first to avoid parasitic wasp damage.

This has been a challenging year for the bees and their ‘owners’ watching over them. What we are hearing: for some, they see lots of bees and see many holes filling quickly while other holes on the same property are filling slowly if they are filling at all. For others it seems they are seeing little or no bee activity in their yard/garden. This leads to many of us to ask, “What did I do wrong?” It is very possible and most likely that you did little or nothing wrong.

Rich: I am going to use my Mason Bee breeding sites and examples from these sites to help explain some of the behavior and results that you are seeing in your yard/garden. I have 18 bee nesting sites on two acres, using many different set ups. I am using different tube styles, different wooden blocks, different house styles, and different nesting materials. I use blocks that are made from many types of wood. Some have square holes, some half round holes, or round holes. Some nesting ‘holes’ are kraft paper tubes with liners and some are reeds. In other words, I am using many different materials to see if there is really a big difference in their preferences for nesting materials. One of my most productive sites would not meet all the criteria on the check list that we sometimes use to help determine if the location is a good one. For example, this site does not get any direct sun. Yet this site (out of 18) produces 25% of all the plugged holes so far this year. Another site about 70 feet away which meets more criteria on our list has produced only 14 plugged holes. So, “What did I do wrong?” That is the question many of us are asking ourselves. I want you to rethink the question. It’s not what did I do wrong, but it should be “What am I doing right?” and “What other things can I do to make it better?” It can be exceedingly difficult to separate out the reason why something did or did not happen when there are so many factors that can affect the outcome.

Back to my two sites: How and in what way do they differ? Looking at three other sites, which are the next three most productive sites (these four produce 50% of plugged holes), I make comparisons mentally listing the differences. One (Z), the poorest producer has direct sun most of the day. The other four (A-B-C-D) are mostly in the shade. (B-S-D-Z) have about the same numbers of cocoons release. (A) had about two times the number of cocoons released compared to the other four sites. (Z) is also in a windy location, (A-B-C-D) are in protected locations. Many other site factors seem to be similar between (A-B-C-D & Z) including mud. Right now, wind, temperature & number of released cocoons look like likely factors to consider for the differences in egg site production at these five sites. I am still looking for other factors to consider. What does this mean for you? It just means this it is complicated. Sometimes it’s easy to figure it out and other times we never do. The best thing you can do is keep trying and if something does not work, twice, change it. Think what has changed if a site is not working well, keeping in mind nature changes many factors like wind, daytime temp, rain +or-, mud production, which plants are in bloom, and others. In case you did not catch it, I stated daytime temperature. It needs to be very cold, well below freezing, for the bees to be affected by cold temperatures. They do not need supplemental heat.

I have heard many claims as to which style of holes the Mason Bee prefer. I remember years ago I had a bee ‘expert’ tell me that Mason Bees will not use holes that are square. I showed him some blocks with square holes that I had been successfully using for five years. These blocks were given to me by a friend who had been used them for over 20 years. I still use them! I said, “Wow! I have been catching imaginary bees for years.” He was not happy to have his expert knowledge trashed. Guess what? Every year the Mason Bees hold a ‘Grand Committee’ meeting where they decide what part of my bee knowledge, they want to trash that year and then they do so. Sometimes it seems like I need to unlearn more than I learn every year, but I do believe I am getting better in helping the native pollinators. Back to holes: in addition to square holes, I use half round holes as well as round holes. I use many different materials for the nesting house, such as many kinds of wood, reeds, Teasel stems, kraft paper tubes with liners, and parchment paper. I also try to provide different hole sizes (3 -9mm). Some of you are thinking “Wait a minute, I was told to do these simple things and I would get Mason Bees in my garden.” You are right. Most of you are using systems designed over many years. These systems make it as simple as possible to keep healthy Mason Bees and most of you are doing just that. We never said it was a 100% perfect process. Keep doing it and you get better as you begin to recognize how each year is a little different from past years. Then you try to figure out why. I enjoy your questions as they are from thinking people and you make me think and question.

So again, back to the holes. Nature never makes perfectly round holes that are always 6 inches deep and always facing the morning sun. We bring these things up because we know if you practice these methods, you will “more likely” have more healthy bees. This is not the only way to have Mason Bees, but just a more efficient way with more success for you and the bees. We can and we do argue about which holes the bees prefer. My take is that the bees will use whatever hole is available if their current preference is not there and also that their current preference changes. What is preferred at one location and situation will not apply at another. I am monitoring over 6 styles of holes totaling over 3600 holes (at numerous breeding locations), and I am still not seeing a strong consistent preference for a hole style. Ask me again in 6 years. I will say this, strongly, the lack of availability of nesting holes is the greatest limiting factor for the number of Mason Bee offspring that each female will produce. As result, female bees will use just about any hole they can fit into. In addition to the above factors, do not forget the importance of mud and blooms. As the season changes, mud dries out flowers die, so we need to monitor what is happening in our garden that may impact the bees.

More about holes: if your nesting system of blocks and/or tubes have more than 50% of their holes plugged, it is time to add more holes. Many of the not yet completely plugged hole are likely active holes. This means a female is filling them and they will fill fast. Keep in mind, if most or all the remaining holes have been rented by a female, then another female will not find a rental and will leave the area. I will use my “A” site to explain. Since I put out the first two block/tube system I have added six more blocks/tubes. Six are now filled and they are working fast on the other two. I think I will have to add at least a few more holes. One question I get about this situation “Is it ok to take down the filled blocks to protect from the parasitic wasps?” My answer it is not yet. Do not move any of the blocks until you take all of them down at the end of the season on June first. Females are more likely to abandon the site if her hole is moved or the site changes too much. Another reason not to disturb the sites is, on numerous mornings at 5:45 a.m. I have gone out to this site and counted the numbers of females that have bedding down in unfilled holes. My greatest count is 34 females ‘sleeping’ in the blocks/tubes waiting for daylight and warmer temperatures.

After the female has mated with a male – and this often happens inside the emergence tube, box or whatever you are using to hold the cocoons for emergence – she leaves the area for two to four days. As she is leaving, she will create a mental map of the location of the cocoon that she just emerged from. She wants to find this location again as in her mind this is where her mother produced her. The female has a strong preference for using the site where her mother produced her. This behavior is called philopatry. We use this behavior to our advantage when we move cocoons to another location for pollination services, knowing that most of the females will stay in the general location where we place the cocoons.

A couple more notes about emergence tubes. Bees are not known to use emergence containers to lay their eggs. Most of the time if you look closer at the bee going into the emergence container it is a male. He is looking for a newly emerged female he can mate with before another male finds her. This is a behavior that you do not need to be concerned about. I strongly encourage you to use an emergence tube or some other container to house the cocoons until the bees emerge. The container offers protection from predators and weather exposure such as too much sun which can kill the bee. It also can keep the cocoons from blowing away.

In July I will be speaking about Mason Bees at the Oregon Master Gardener Association Mini College, if you want to hear me talk more about Mason Bees. There will be a Q&A session afterward.

Again, we enjoy your questions and they make us consider possibilities as we continue to learn more about mason bees.

Rich

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