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