Bee disease spreading via flowers

Date:
July 23, 2020
Source:
Cornell University
Summary:
One in 11 flowers carries disease-causing parasites known
to contribute to bee declines, according to a new study that
identifies how flowers act as hubs for transmitting diseases to
bees and other pollinators.



FULL STORY ==========================================================================
One in 11 flowers carries disease-causing parasites known to contribute
to bee declines, according to a Cornell University study that identifies
how flowers act as hubs for transmitting diseases to bees and other pollinators.


==========================================================================
The study, published July 20 in Nature Ecology and Evolution, also found
that one in eight individual bees had at least one parasite.

The study was conducted in field sites in upstate New York, where the researchers screened 2,624 flowers from 89 species and 2,672 bees from
110 species for bee parasites through an entire growing season. They
used molecular data to identify five common protozoan (free-living, single-celled) and fungal parasites.

"We know very little about transmission of these diseases," said senior
author Scott McArt, assistant professor of entomology in the College of Agriculture and Life Sciences. "Our study shows that transmission can
likely occur on a lot of different flowers, and the amount of disease in a community is shaped by both the floral community and the bee community."
The researchers found three main factors -- flower abundance, numbers
of social bees and bee diversity -- played roles in disease transmission.

As the season progresses, the number of flowers goes up. For example, in
the fall, flower-laden goldenrod dominates many New York fields. At the
same time, the proportion of flowers with parasites goes down, lowering
the risk that a bee will pick up a parasite when it visits a flower.

"That has really important conservation implications, because if you
want to limit disease spread, just plant a lot of flowers," said McArt,
adding that planting flowers also provides food for pollinators. "It's
a win-win: If we plant flowers and create a lot of forage, we can also
dilute disease." The study revealed that social bees, such as honeybees
and bumblebees, were more likely to be infected with parasites than
solitary bee species. The researchers found that later in the season, the number of social bees increases, while bee diversity overall decreases.

And as a general rule, diversity of species lowers the spread of disease.

"Both bee diversity and fewer of the social bees make it less likely for
bees [overall] to be infected. That's another win for conservation: if
we promote bee diversity, there will be less disease," McArt said. High
numbers of infections in the social species may also spill over to infect
other species, he said.

Future studies will try to determine whether increased flower abundance
cancels out the negative effects of increased numbers of social bees
combined with lower overall bee diversity later in the summer.

More study is also needed to understand why social bees are so susceptible
to parasites, whether they lack defenses and if they are sharing disease
in close colony quarters.


========================================================================== Story Source: Materials provided by Cornell_University. Original written
by Krishna Ramanujan. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Peter Graystock, Wee Hao Ng, Kyle Parks, Amber D. Tripodi, Paige A.

Mun~iz, Ashley A. Fersch, Christopher R. Myers, Quinn
S. McFrederick, Scott H. McArt. Dominant bee species
and floral abundance drive parasite temporal dynamics in
plant-pollinator communities. Nature Ecology & Evolution, 2020;
DOI: 10.1038/s41559-020-1247-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200723172212.htm

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