Identifying pollen sources used by honey
bees in central Ohio's agricultural landscape
Chia-Hua Lin and Reed M. Johnson
Department of Entomology, The Ohio State University
Exposure of honey bees to corn seed
treatment dust via pollen forage
“Seed dust” generated by a pneumatic seed planter
http://afschem.com/
Insecticides used in seed treatments were detected on dandelion flowers near cornfields, posing a potential threat to foraging bees. (Krupke et al. 2012)
Potential spring foraging habitats for bees in an agricultural landscape
Fields & margins
Forests
Roadsides Residential yards
What pollen sources do bees use during spring corn planting? 2013: 3 sites
Where are the major pollen sources in this agricultural landscape?
2014: 6 sites
National Land Cover Database 2011
Landscape analysis
Columbus ★
Non-crop, semi-natural
Corn (2013)
Legend
Other crops
Tree canopy
Residential
Three Two
One
0
20
40
60
80
100
% la
nd
in 3
km
rad
ius crops
seminatural
residential
Two
3 km
Three study sites, 2013
One Three
• 6 colonies, 2 of each:
- New from packages (small)
- 8-framed nucleus (medium)
- Overwintered (large)
pollen traps
Pollen collection
• April 29 – June 11
• Collected twice weekly:
- dead bees from 4 colonies
- pollen from 2 colonies
Experimental setup (2013)
Foragers are specialized
Each forager only collects pollen or nectar from one flower type
Foragers are specialized
Collecting pollen with Sundance pollen trap
Pollen trap “OFF” Pollen trap “ON”
Bottom mounted pollen trap
Pollen sources change over time
Samples collected from the same site, different dates
April 12 April 27 May 1 May 5
May 7 May 9 May 13 May 17
Pollen sources vary by location
Samples collected from different sites on May 30, 2014
Identifying pollen sources
10%
1. Take 10 % of the sample 2. Sort by color 4. Weigh each category
Corbicular pollen sorted by color
5. Prepare slides
6. Identify and determine relative proportion of pollen sources.
• Staining* – minimal processing time, cost-effective, low resolution
• Acetolysis* – time consuming but better resolution in some plants
• Electron microscopy (SEM)
* Examine with light microscope at 400X or 1000X
** Pollen grains may change size and shape depending on the method of preservation. Therefore, be consistent with the method you use if possible.
Common methods of pollen analysis
Size and shape of pollen grains (Scanning Electron Microscopy)
Most pollen grains range between 10 – 150 μm in diameter.
Pollen morphology - apertures
Image source: Furness & Rundall (2004) TRENDS in Plant Science
Ingredients:
• 7 g gelatin (one individual package)
• 24 ml water
• 21 ml glycerin
• Very small amount of crystalline basic fuchsin (from chemical suppliers, e.g. Fisher Scientific)
Basic Fuchsin Jelly recipe for pollen staining (modified from Techniques for Pollinator Biologists by Kreans & Inouye, 1993)
Mounting pollen on slides
Place small drops of melted jelly on glass slides. Cool to room temperature
Smear a small amount of pollen on jelly, reheat to melt, and add cover slips
Pollen identification
• Compare sample with reference pollen collected from fresh flowers (best option if possible)
• Identification keys
• Online image databases
Pollen images database
• Introduction to Pollen Analysis (based on fossil pollen and spores, but a good place to learn the terminology) http://www.botany.unibe.ch/paleo/pollen_e/index.htm
• Australian Pollen and spore atlas: search by morphological characters http://apsa.anu.edu.au/
• PalDat: search fossil and recent pollen http://www.paldat.org/
• USDA pollen image collection, organized by family http://pollen.usda.gov/Photographs.htm
Aster Daisy Thistle
Ohio pollen images library
Sweet clover White clover Basswood Sage
Blueberry
Deadnettle Dandelion Ash Hawthorn
Perc
ent
po
llen
co
llect
ed b
y w
eigh
t
4/29 5/02 5/09 5/06 5/13 5/16 Date
dandelion
mustard
other herbaceous
rosaceous
ash
maple
other woody
willow
honeysuckle
Herbaceous plants
Woody plants
corn planting 5/3 – 5/16
Spatial and temporal variation of pollen sources (3 sites)
One
Three
Two
Perc
ent
po
llen
co
llect
ed b
y w
eigh
t
dandelion
mustard
other herbaceous
rosaceous
ash
maple
other woody
willow
honeysuckle
Herbaceous plants
Woody plants
Phenology of honey bee pollen loads
Sample dates
average
0
20
40
60
80
100
WB FSR CH
% p
olle
n c
olle
cted
b
y w
eigh
t herbaceous
woody
0
20
40
60
80
100
WB FSR CH
% la
nd
in 3
km
rad
ius
crop field
seminatural
residential
Pollen sources in the context of landscape
One Two Three
One Two Three
Study sites in Ohio
Columbus ★
Non-crop, semi-natural
Corn (2013)
Legend
Other crops
Tree canopy
Residential
CH FSR
WB
0
20
40
60
80
100
WB FSR CH
% la
nd
in 3
km
rad
ius crops
seminatural
residential
3 km
Three Two
One
One Two Three
• 6 colonies, 2 of each:
- New from packages (small)
- 8-framed nucleus (medium)
- Overwintered (large)
• April 29 – June 11
Dead bee traps
• Collected twice weekly:
- dead bees from 4 colonies
- pollen from 2 colonies
Experimental setup, 2013
WB FSR
CH average
Note: whether the residues resulted from corn dust or from pre-existing residues in soils or plants could not be differentiated
Bee mortality & neonicotinoid residues in pollen
One Two
Three
• Mass-flowering trees and shrubs were the primary pollen sources used by honey bees during spring corn planting.
• The majority of pollen forage, at planting, was supplied by small amounts of semi-natural and residential areas in the landscape.
• Trends for increased bee mortality and increased levels of insecticide residues in bee-collected pollen during planting.
• Only one year of data. More research is needed.
Conclusions - 2013 study
Consistent results from three study regions
• Ohio (this study), Iowa, and Guelph, Canada
• Honey bees collected pollen largely from trees and woody plants (apple, hawthorn, willow, maple, etc.) during the time of corn planting.
• Across all three regions, the highest levels of pesticide residues in bee-collected pollen occurred during the approximately two-week planting period.
• Comparison of pollen diversity and nutritional quality for honey bees in urban vs. agricultural landscapes (Douglas Sponsler, OSU)
• Bee health surveys: We need your help!
We invite beekeepers in Ohio to participate in a brief survey about the landscape around their apiaries and the health of their bees.
online: http://go.osu.edu/springbeesurvey
Open through August 31, 2014
What about bees in other landscapes?
Acknowledgements Collaborators:
• Dr. Karen Goodell
• Doug Sponsler
• Rodney Richardson
• Juan Quijia Pillajo
• Michael Wransky
• Brendan Zapp
Study sites:
• Joe Davlin (OARDC Western Branch)
• Nate Douridas (Farm Science Review)
• Ohio Beekeepers
Funding:
• Pollinator Partnership & Corn Dust Research Consortium
• Ohio State Beekeepers Association
• Tri-County Beekeepers Association
Field & lab assistance:
• Howard Rogers
• Galen Cobb
• Jessie Wallace
• Evan Oltmanns
• Lienne Sethna
• Jordan Rose
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