Pests imacting your nesting bees

If you don’t harvest your cocoons in the fall, or leave your cocoons out all summer long after your particular bee species has finished their season, pests will impact your nesting bees. Why?  You are combatting nature by having too many “good things” in one place.  Nature wants there to be less consolidated bees, and allows pests to bring down your mason bee numbers.  From birds having a bunch of holes to peck into all in one place, to pollen mites being reintroduced because they weren’t harvested the previous year, nature will win out. We’d like to help you work
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Pollen Mites

Problem: A pollen mite’s role in life is to eat pollen.  They hitchhike on backs of insects from flower to flower to find more pollen.  Unfortunately, they also hitchhike into nesting straws and begin eating the mason bee’s collected pollen.  Pollen mites are found throughout North America- more in moist environments than arid. Photo of the first stage of pollen mites in a straw. The pollen mite either eats the egg and then the pollen, or just the pollen and the larva starves.  The orange mass is mite feces.  The mites themselves (Krombein’s hairy-footed mites) are clear and you need
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Monodontomerus (Parasitic wasp)

Problem: The monodontomerus, or “mono” is a parasitic wasp that lays its eggs on the larva, usually within the cocoon of the mason bee.  The eggs then hatch and the mono larvae (10-15) eat the mason bee larva.  They take about 6 weeks to develop from eggs to emerged adults, so if there are flying adults of monodontomerus among the cocoons, or thin-walled nests while the mason bees are still larvae or early pupae, there will likely be a lot of dead mason bees and another crop of mono flying soon. Mono females typically deposit their eggs through the side
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Ants

  We’ve heard that ants can create a nuisance for nesting bees.  Buff in Beaverton, OR reported this situation: “One daughter reported seeing ants going in openings and exiting with something white.  She thought it might be pollen.  That house is facing East and is on a fence. What can we do to stop the ants?  We don’t want to use anything caustic that would harm the bees and cocoons.” That “something white” was a recently laid egg, about the size of a grain of sand. What to do: This is tough, as ants can, and will, find a path
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Carpet beetle larva

  Problem: The carpet beetle larva eat mason bee cocoons.  Mud plugs or mud divisions don’t concern them. They are known to be scavengers and may just follow after another insect has ravaged your tube/reed.Control solution: Take the straws down after the mason bees are finished for the season. Store the straws upright in a box or mesh sack in a shed or garage. During harvest, as you sort through the straws and find this pest, eliminate them.  If you find this in one of your sampled straws (see harvesting), we recommend that you open all of your straws.  You don’t
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Stelis bee

Problem: The stelis bee, or “cuckoo bee”, gets its name from being a parasite that lays its eggs in the nest of mason bee.  They lack the ability to transport pollen, and so lay their eggs in the pollen mass carried by the mason bee.  When the stelis egg hatches, it kills the mason bee egg or young larva and then consumes the remaining pollen. The best means of determining this pest’s cocoon is by the “spaghetti” shaped feces rather than brown straight feces. The cocoon is also very firm in comparison to the mason bee. Control solution: Remove stelis
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Ptinus Beetle

Problem: The beetle ptinus eats the larva and cocoons.  If left unchecked, this scavenger has the potential to destroy many of your mason bees if the numbers become huge. Control solution: During harvest, remove all eggs of this pest.  
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Earwigs

Problem: You find earwigs in your cocoon release box, in your tubes, and everywhere around the nesting house.  What’s going on? Earwigs are opportunists and more scavenger than predator.  Leftover pollen is wonderful.  Do they go for the egg if the nesting female has just laid it and is out gathering mud?  Probably.  It is very likely that the mason bees might nest elsewhere. Control solutions: Loosely roll up a section of newspaper, bind it with a rubber band or string, dampen it, and place this “trap” in(?) or physically attached to the nesting house where you think they might
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Birds nesting or playing with straws

Problem: If there is leftover space above your straws, it may become an attractive nest location for birds.  These birds will naturally have a better chance at eating the nesting mason bees. Control solutions: Fill the cavity with sticks, rocks or something that eliminates the cavity. Or, place chicken wire or hardware cloth (1/2″-3/4″ opening) over the front. Problem: Birds (typically Crows, Stellar Jays, Blue Jays) pull the straws out of the mason bee house.   Control solutions: Apologize to the hovering mason bees, and place their straws back into the mason bee house. Place chicken wire or hardware cloth (1/2″-3/4″
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Woodpeckers

Problem: Woodpeckers have created natural holes for mason bees in the wild.  They are only doing their job when they rid your straws of the tasty larva and cocoons within. Control solutions: During the active mason bee season, place hardware cloth (1/2″-3/4″ opening) over the front. After the season is complete, take the straws out of the environment.  
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