Bees "entomb" pesticide-laced pollen | Pesticide Action Network
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Bees "entomb" pesticide-laced pollen

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In an apparent, and failed, attempt at self-defense, honey bees are sealing off pesticide-laced pollen.

U.S. entomologists published a study two years ago that described a newly observed phenomenon in honey bees, now known as entombed pollen: food stores sealed off by bees after being deposited in the hive. That pollen was much higher in pesticide residues than any other pollen stored in the hive, and correspondingly had no detectable bacteria or fungi. Hives with entombed pollen were more than twice as likely to collapse later in the season than hives without it.

New research confirms this trend. According to leading U.S. bee researcher, Dr. Jeff Pettis, "The presence of entombing is the biggest single predictor of colony loss. It's a defence mechanism that has failed." And although once thought to be rare, entombing is showing up with greater frequency in U.S. research on honey bee declines, according to recent coverage by The UK Guardian.

The presence of entombing is the biggest single predictor of colony loss. It's a defence mechanism that has failed. - Dr. Jeff Pettis, USDA

Well-designed tests conducted in that initial study showed no direct toxicity in bees that ingested the highly contaminated pollen compared to pollen more typically found in hives, which has significantly lower pesticide residues. Researchers concluded that entombing is an indicator of exposure to a mortal risk factor. USDA’s Pettis, who was one of the collaborating researchers in the 2009 study, gave testimony to the UK Parliament last week, reporting that researchers are seeing more incidences of entombed pollen. He sees this as an indicator that bees are detecting the combination of high pesticide contamination and low microbe activity, and attempting to protect the hive from harm with a propolis-sealing strategy similar to that used by bees to quarantine hive invaders, such as a dead lizard or mouse.

According to The Independent's coverage of his testimony, Pettis stressed that the interactions between two or more of the “3 Ps”— poor nutrition, pathogens, and pesticides — are driving colony collapse disorder, rather than any one factor." Distancing himself from recent calls to ban neonicotinoid pesticides to protect pollinators, Pettis further stated that, "pesticide is an issue but it is not the driving issue."

Tom Philpott of Grist analyzes the situation somewhat differently, noting that, “This bit of testimony shines a harsh spotlight on pesticides among the ‘mix of factors’ that appears to be killing honeybees. If the entombing phenomenon is ‘the biggest single predictor of colony loss,’ then the presence of pesticides, if that is indeed what's driving bees to entomb cells, appears to be the factor that tips troubled hives into collapse.”

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Mrs. D's picture
Mrs. D /

I've been wondering. A colony of bees has taken up residence in a hollow tree in our back yard. Someone told me that it is most likely a colony of feral honey bees. I would like to encourage them to come back year after year. They were there last year and they are there again this year. Will they continue to come back or do colonies like that move around? How can I encourage them to stay? I have a small organic home vegetable garden and also flower gardens around. I never use pesticides. I also have a variety of fruit trees and vines around the periphery of my back yard. Also, are these bees dangerous? My husband doesn't want to mow the lawn in the area of that tree! I like having them for several reasons, one being that they are fun to watch! I also feel that my flowers and vegetables are pollinating a lot better since they arrived!

Beemidwife's picture
Beemidwife /

Bees stay in their hive year round so the ones you are seeing have just become active again after the winter. They will stay there unless something about the hive forces them to move. As they outgrow the space they will make a new queen and some of them will go in search of another home.

It is not likely that they will sting your husband, even if they come buzzing around him. I used the small tiller next to one of my hives last week. It is possible he will get one or two stings if they feel threatened, but not a full on attack like yellow jackets or hornets will do.

I encourage you, and everyone to set up a backyard hive. It's fun and easy. See for some information of keeping bees naturally.


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