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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