Better-fed honey bees fight off harmful parasite

Bees on blackberries
Honey bees pollinate blackberry blossoms at OSU's North Willamette research station.

Well-nourished honey bees are better at fighting off a serious microscopic parasite that weakens their immune systems and threatens the health of colonies, according to research by Oregon State University Extension faculty 

The parasite Nosema ceranae is a fungus-like organism that gets into the digestive systems of bees. At high levels it disrupts their protein metabolism, weakens their immune systems and causes the next generation of bees to be malnourished. A severe infestation can deplete the population of bees within a colony and may eventually cause the colony to collapse.

Ramesh Sagili, Extension honey bee expert, and his student Cameron Jack fed European honey bees--those most commonly used to pollinate commercial crops--with varying amounts of wildflower pollen and then exposed them to the parasite.

The bees that ate more and more-varied pollen survived the infestation much better than did the bees on leaner diets, even though the better-fed group had more N. ceranae spores in their gut tissues.

“It may seem counterintuitive that the protein from the pollen enhanced the reproduction of the pathogen,” said Sagili. “But the important point is that the better-fed bees were able to compensate for its negative effects.”

The findings suggest that letting honey bees forage on a greater quantity and variety of pollen--their only protein source--makes them more resilient against bee pests and could help to stem worrisome declines in bee populations.

Pollination by honey bees and other insects is worth about $15 billion in the U.S. Sagili estimates that honey bees pollinate some $500 million worth of Oregon crops yearly.

Source: Ramesh Sagili, Extension honey bee specialist

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