by Master Gardener, Brenda Johnson
That BUZZ is excitement about a fantastic little pollinator Osmia
Lignaria a.k.a. the Orchard Mason Bee, Blue Orchard Bee, Orchard Bee
and Mason Bee, a North American native pollinating bee. They are members of the genus Osmia that carry pollen on their bellies
rather than on their hind legs and they nest in holes. They are one of 140
species of Osmia in North America
(4000 species of native bees) and
are so efficient at pollinating native crops that they are one of the native
bees being managed in agriculture. Insufficient doses of pollen can result in
reduced seed set and undesirable shaped fruits.
Why are they called Mason bees? When building their nests, Mason
bees use clay to make partitions and to seal the entrance. This unique
mud-building behavior leads to their common designation as masons.
Mason bees are about the same size as a honeybee though
smaller and are a dark metallic blue, not striped brown and orange like the
honeybee. When in flight they may be mistaken for a black fly. Look closely, flies don’t have antennae, bees
do. They are about ½ inch long: females
about .55 inch, males about .43 inches long.
No need to fear, male
Mason bees have no stingers and having no queen to protect and all of the
females are fertile, they’re not aggressive.
Only females can sting, though not likely, since the sting is
modified from egg-laying structures. Should there be an incident, her
sting is more similar to a mosquito bite than your average bee sting.
Being solitary, like most native bees means that each one
tends to its own brood, instead of having a queen and worker bees. However,
they build their nests together with others of their kind, much like our apartment
living. They will also nest in other locations such as hoses, bamboo, abandoned
pipes or holes left by other boring insects.
Females generally create seven to eleven cells per nest.
One can make fancy houses or use untreated lumber (4”x6”) or
any piece of wood into a nesting block. Holes can be drilled in the wood on 3/4
“centers and should be 4-8" deep, not going completely through to back side. Drilling holes smaller than a 5/16” diameter
tends to produce a higher number of male bees. Increase sanitation with use of parchment
paper or other types of liners to line the holes, just don’t use plastic. Paper lining can be removed each season to
prevent the buildup of fungi and bacteria.
If using PVC pipe filled with paper straws, bamboo, or tubing,
the back ends need to be sealed so no invaders can get in through the back
door. Masons will occupy paper tubes or paper straws used the previous year. Regardless of style,
nests need to be placed on a south-facing garage, house, or garden shed wall
with the cavities tilted downward to limit collecting water. Wind is also a hazard so a secure mount is
needed to keep eggs or young larvae from falling out and young babies would be
too weak to crawl back inside.
Early spring is prime time to set out your
nests. Mason bees are active in the
early spring and summer, mid-March to late May or early June, the time when
most of the fruit trees are in bloom.
During this time, female mason bees spend their days buzzing around,
gathering pollen and nectar from flowers within a short distance from their
nest, about 300 ft. (100 yds.). This
mixture of pollen and nectar becomes the food, “dough ball” that is placed in
each chamber for the new egg. When the
right amount of food has been placed in the chamber the female backs in and
lays a single egg into the “dough ball”. Then she partitions the cell with a
mud wall and starts all over again repeating the action until she has filled
the entire tube. When the female is
adding her final mud plug, she’ll go around and around the opening as she works
to close the egg chamber, then flies away looking for another hole.
Individual pheromones help them identify their own hole so
if she accidentally goes into another bee’s hole, she will quickly back out and
find the correct nest.
The first brood cells that the Mason bee makes (those that
are furthest back) will develop into female bees, while the ones closer to the
entrance will become males. Thus the males emerge first, anywhere from a few
days to a few weeks before the females. They spend their time foraging for
nectar to build up their strength and buzzing around the nest waiting for the
females to emerge. During this time, they do a bit of pollinating but the real
contribution made is mating with the females.
Once all the females have been mated, the males die then it is center
stage with an all-girl show. Brood nest
building is totally up to the female.
Bees also suffer from predators, and the brood closer to the
entrance would be the first to become candy-like food to certain species of
flies and wasps that chew through the plugs.
In this way a hungry invader is likely to eat the sacrificial males only
and leave the girls safe and sound but sometimes, females often intentionally
leave the first cell empty. As in the world
of bees and other species it is all about protecting the females and only a few
males need to survive to mate the next spring.
Predators are more apt to take down a nest before a disease can.
The best way to avoid predators is to store the nest in a garage
or shed at the end of the active period.
This will give the bee’s added protection from predators and parasites,
yet will allow them the needed cold temperatures to break hibernation. If
desired, bee emergence can be delayed for a short period by refrigerating the
block in the spring until you are ready for the bees to emerge. Bees will need
three days to warm up following refrigeration.
Mud, mud, mud is a
must have. It is vital for the ladies to
have a mud area available, meaning an open place with no mulch and no grass.
Clay soil works best, so no sandy or highly amended soil. It is best to
keep the mud area a small distance from the nest so weak emerging bees can’t
fall into it.
Pollen, pollen,
pollen is another must have. Mason bees
will move to other areas if there isn’t enough pollen in your yard. Flowers with colors such blue, purple, and yellow (clover and dandelions) are desirable
along with the big-leaf maples. Be on
alert to which plants your bees like to visit.
Perhaps you currently have some of the following plants.
- Trees and Shrubs: Eastern Redbud, Apple, Currant, Gooseberry,
Roses (early blooming, singlevarieties are best), Raspberry, Blackberry,
Willow, Plum, Peach, Nectarine, and Viburnums.
- Perennials and Annuals: Strawberry, Geranium, Wildflower, Dandelion
(mow them while fruit trees are in bloom – you really want them working your
fruit and flowers not the lawn).
Another note, native plants attract native bees, whereas
exotic plants attract non-native species.
By autumn, Mason bees have laid their eggs in the nest and they
are developing stage by stage. At this
point no bee tends the brood. The egg
hatches and the larva eats the
stored food of pollen and nectar, develops
on its own, and spins a cocoon,
then hibernates in a larval stage known as the prepupa and waits for the first warm days of spring to emerge in
your garden.
When scouting out your garden for these iridescent, metallic
dark blue jewels, remember you can develop a partnership. Your garden can be a Buzz with excitement
year after year as long as the bees have sufficient shelter and food, plus you
get great fruit and fantastic gardens. MASON
BEES ROCK because they are the best little pollinators.
