Let’s have a little sympathy for the native mason bees that have been getting more and more popular with backyard gardeners.
A nasty predator called the Houdini fly, which arrived from Europe a few years ago, is coming for them. It’s starving them to death.
Haven’t heard of mason bees, which get their name from their practice of sealing off their eggs with a wall of mud?
This unassuming, solitary bee has not gotten the recognition it deserves.
Mason bees are so good at pollinating fruit trees that they are also known as orchard bees.
Says the U.S. Department of Agriculture, “Honeybees are very important to commercial agriculture, but native bees like the blue orchard bees are better and more efficient pollinators of native crops.”
If there ever was a personification of the Pacific Northwest, it is the mason bee. It prefers to be by itself. It is mellow, and male mason bees don’t even have a stinger. Females have a stinger but are not aggressive, and even if they sting, they don’t sting very much, like a honeybee does.
But about the Houdini fly.
It got that name because it sneaks in and steals food. Scientists call that a kleptoparasite.
The fly lays its eggs right by where a mom mason bee has laid her eggs. To nurture her young bees when they hatch, she also has left pollen and nectar for them.
As thieves, the Houdini flies use the fact that their young hatch earlier than the mason bee young. The young flies proceed to eat the pollen left for the mason bees, which then starve. Nature can be cruel.
In 2022, Crown Bees of Woodinville, a major mason bee supplier, found Houdini fly maggots in 25% to 35% of places where you’d find mason bee cocoons.
In 2020, says Dave Hunter, founder and owner of the company, the maggots were found in less than 1% of such sites.
Crown Bees was started in 2008, and that year Hunter sold maybe 1,000 bees. Now Crown Bees sells 500,000 bees in the United States and Canada.
Hunter began alerting his colleagues and researchers.
In February 2020, the state’s Department of Agriculture issued a Houdini pest alert.
Since then, “it’s significantly worse than two years ago,” says Katie Buckley, pollinator health coordinator for the state. The fly has spread.
Steve Peterson, president of the Orchard Bee Association and a California mason bee grower, said the fly has been reported in the port cities of Seattle, Portland and Vancouver, B.C.
He’s thankful it hasn’t yet arrived in his state.
It really does seem that whatever the species of bee, they just can’t seem to get a break.
In 2019 there was the discovery in this state of the murder hornet, now known as the Northern giant hornet, the first detected in the Pacific Northwest. On Dec. 19 of that year, a Blaine man stepped out onto his front porch and saw a dead one: “It was the biggest hornet I’d ever seen.”
The hornets decapitate honeybees, and can take out thousands in a few hours.
That set off a massive effort to find, trap, vacuum up and kill the hornets. In 2022, says the state, no giant hornets were detected here.
Hunter is hoping for a similar effort to contain the Houdini flies.
The other big mason bee supplier here, Jim Watts, who owns Rent Mason Bees and Watts Solitary Bees in Bothell, says: “If we don’t do anything, it’ll be a disaster. It’d wipe us out pretty quickly.”
Hunter has been in contact with USDA researchers, who have forged an agreement with his company to develop a lure to attract the Houdini fly to a pest strip.
It wasn’t that many years ago that few gardeners knew about the mason bees that always have been living among us.
The shiny, dark-blue mason bee can be mistaken for a common household fly.
Mason bees don’t build hives. The females build nests inside holes left by tree-boring insects, or, if they decide to use your house, in a crevice behind a home’s shingles. They don’t damage homes.
As backyard gardeners discovered mason bees, numerous companies began offering bee houses that hold a bunch of hollow tubes for the eggs. Some were simple wood blocks with holes drilled into them.
It is such “bee hotels” that the Houdini flies infested.
In the wild, mason bees spread out widely to find places to lay their eggs. The wood blocks concentrate the eggs in one handy location for the Houdini fly to linger and pounce.
It is the hobbyists who unwittingly have helped spread the Houdini fly, says Watts.
“It’s a minority of gardeners, but it doesn’t take many. They don’t clean their bees when they’re in the cocoon stage [to get rid of infestation], they share them with each other,” thus passing on any infestation, he says.
The Oregon State University Extension Service explains the cleaning process involves cool water — so as not to wake up the bees from their cocoons — as part of a very diluted bleach solution.
You can also pick out the Houdini fly maggots waiting to hatch and squeeze them to death. Who knows how many backyard gardeners would sign up for that task?
Hunter’s company offers a $5.95 Bee Guard bag made out of fine-mesh organza fabric to place around the mason bee blocks. It allows air in, but not Houdini flies. Or you can make your own.
With Watts’ rental business, it is the company that deals with any infestation. Customers pay $75 for 50 to 60 mason bee cocoons, a nesting block and a wooden house. At the end of the season, they send everything back. He has 3,000 customers for the rental business, and sells 1 million cocoons a year, mostly to commercial orchardists.
Presumably there’ll be a solution.
That’s for the Houdini fly.
Another invasive species going after bees is mites, single-cell fungi that spread disease and parasites, says Diana Cox-Foster, a bee researcher with the USDA in Logan, Utah.
Really, it doesn’t take much.
A jet flight, a ship’s cargo, an air express package. The invasion will continue.