Institute of Ag Professionals

Proceedings of the

2014 Crop Pest Management Shortcourse &

Minnesota Crop Production Retailers Association Trade Show

www.extension.umn.edu/AgProfessionals

Do not reproduce or redistribute without the written consent of author(s).

Causal Factors of Honey Bee Colony Declines

Are neonicotinoids involved?

Galen Dively, Emeritus Professor

Department of Entomology

University of Maryland

College Park, MD

galen@umd.edu

Are neonicotinoids involved?

Stress factors affecting colony health

Routes of pesticide exposure to bees

Residue levels in pollen and nectar

Fate of residues in honey bee colonies

Summary of lab and field colony studies

End with what is really involved

http://www.nap.edu/catalog/11761.html

North America Pollinators

• National Academies of Science

• Status of Pollinators in North

America

• 2007

• Pollinators are in decline

Bumble

Bees

Leafcutter Bees

Mason bees

Squash Bees

Pollinators at Risk and Value

• Biesmeijer et al. 2006 Science 313 (5785) Parallel

declines in pollinators and insect-

pollinated plants in Europe.

Gallai et al. 2008 Ecological Economics

Worldwide value of pollination estimated

to be 153 billion Euros or 9.5% of

Agricultural production.

Honey bee pollination in the US supports

an estimated $15 billion worth of

agricultural production, including more

than 130 fruits and vegetables.

www.sciencemag.org

With Pollinators

Without Pollinators

About 1/3 of our diet directly or

indirectly benefits from honey bee

pollination.

Many tree nuts, berries, fruits and

vegetables are dependent on

pollinated by honey bees.

Large scale

Agriculture

Urbanization

Habitat destruction

Monocultures

Varroa mites spread

rapidly through US

Imidacloprid was

introduced

CCD

Honey Bee Colony Losses – A Historical Perceptive

10-15% - Prior to the introduction of parasitic mites in mid 1980s.

20-25% - After mites were introduced.

Surveys of colony losses

Bee Informed Partnership Project

Since CCD, losses have been

around 30-35%, though the

incidence of CDD are declined.

Beekeepers say up to 15% loss

would be sustainable.

Colony Collapse Disorder Symptoms

Rapid loss of adult worker bees

Small cluster with queen is always

present

No dead bees in or around the colony

Presence of brood and food stores

Higher pathogen loads (bacteria,

viruses, fungi) in CCD colonies

No pattern of exposure or association

with pesticide levels

No single stress factor found

NOT ALL BEE MORTALITIES ARE CCD

SIMILAR EVENTS OCCUR BEFORE

Major Migratory Routes of Honey Bee Colonies

California almonds require

1.5 million honey bee colonies

each year; that represents

more than half of all managed

colonies In the U.S.

Management and Nutritional Stress

Bacteria

Parasitic mites Other Insects

Fungi

Nosema

Viruses

Fungi

Nosema Viruses

Management and Nutrition

Secondary Pathogens

Stress Factors contributing to Bee Declines

Pesticides Varroa Mites

Honey Bees ……. Flying Dust Mops

Foraging area - 2 mile radius or 8,000 acres

Exposure via nectar EXPOSURE via NECTAR/PLANT EXUDATES

EXPOSURE via CONTAMINATED WATER

Neonicotinoids

Pesticides found in bees and hive matrices

Source: Mullin et al. (2010) PLoS ONE

350 pollen samples 98 pesticides (and metabolites)

Avg 7.1 different pesticides each

Up to 31 pesticides in one sample

99% with residues

259 wax samples 87 pesticides (and metabolites)

Avg 8 different pesticides each

Up to 39 pesticides in one sample

100% with residues

140 bee samples 46 pesticides (and metabolites)

Avg 2.5 different pesticides each

Up to 25 pesticides in one sample

92% with residues

Pesticides found in pollen foraged

Source: Pettis et al. (2013) PLoS ONE

Pesticides found in hives (beebread samples)

Source: National Honey Bee Disease Survey - unpublished

Coumaphos

Fluvalinate

The Case of The Vanishing Bees

Pesticides & The Perfect Crime: In the widespread bee die-

offs, bees often just vanish. One beekeeper calls it the

Perfect Crime- no bodies, no murder weapons, no bees.

What’s happening to the bees?

May 2, 2014

Neonicotinoid Insecticides

imidacloprid (Admire Pro, Admire, Alias, Provado, Gaucho,

Leverage, Merit, Premise, Trimax Pro, other generics)

thiamethoxam (Platinum, Actara, Cruiser, Endigo)

dinotefuran (Venom), clothianidin (Belay, Clutch, Poncho)

acetamiprid (Assail), thiacloprid (Calypso)

Widely used as seed dressings, soil-applied, soil drenches, in-

furrow, chemigation, and foliar treatments

Labeled uses on many crops, turf, ornamentals, trees, as well as

products for termite and flea control and home garden use.

Relative Toxicity of Neonicotinoids and Other Insecticides to

Honey Bees

Nitro subgroup (imidacloprid, thiamethoxam, clothianidin, dinotefuran)

- LD50 is 0.02-0.08 ug/bee (highly toxic)

Cyano subgroup (acetamiprid, thiacloprid) - LD50 is 7-15 ug/bee

Other insecticides (acute LC50 in ug/bee):

Coumaphos – 3-6 Carbaryl - 1.34

Tau-fluvalinate – 9.4-66 Dimethoate - 0.18-0.90

Azinphos-methyl – 0.43 *Fipronil - 0.004-0.006

Chloropyrifos – 0.11 Malathion – 0.73

Pyrethrins – 0.03-0.8 Methomyl - 1.29

Endosulfan – 22 *Oxamyl - 0.47

*Carbofuran – 0.16 Spinosad – 11.5 ppm

*Acephate - 1.2 Diazinon – 0.22

• Are the bees exposed to neonics?

– How, how much, how long, how frequently

– Which life stage?

– What combinations?

Neonicotinoid risk = Toxicity x Exposure

More complex than a single LD50!

• Are the neonics toxic to bees?

– Acute, chronic and sub-lethal

– Individual level and colony level

– Indirect effects

– Additive and synergistic effects

Results of laboratory studies on neonicotinoid effects

on individual honey bees:

Many studies show that exposure levels above 20 ppb of imidacloprid

can cause subtle physiological and behavioral abnormalities in honey

bees, including reductions in associative learning, queen fecundity and

foraging activity, as well as increased susceptibility to other stresses.

Many lab tests have investigated effects at doses above the field-

realistic range, results are conflicting, and some disagreed with the

effects observed in field studies.

Measure sublethal effects on individual bees by exposing them to

single doses in sucrose water or contaminated pollen. Hard to

extrapolate lab results to the health of a functional colony which can

compensate for many stresses.

Primary routes of neonicotinoid exposure to bees:

direct exposure from pesticide applications.

- direct contact while foraging during bloom

- exposure to residues after heavy dew

- drift on non-crop flowering vegetation

Synergistic interactions between neonics and medications increase

toxicity and potential sublethal effects to bees (Johnson et al. 2009,

Hawthorne and Dively 2011).

Certain azole fungicides can synergize neonics and increase their

toxicity to honey bees by over 1,000 fold (Iwasa et al 2004).

Some fungicides alter honey bee foraging behavior and their

susceptibity to Nosema infections (Pettis et al. 2013).

Mounting evidence that fungicides may interfere with the conversion

of pollen into bee bread.

Accumulation of coumaphos in hive wax may alter certain metabolic

pathways in bee larvae and pupae (USDA Bee Lab, Beltsville, MD)

Direct exposure from neonicotinoid applications

Direct exposure from neonicotinoid applications

2014 EPA regulations for foliar use of neonicotiniods

To minimize exposure to bees and other pollinators on all

clothianidin, dinotefuran, imidacloprid, thiamethoxam, or

acetamiprid products registered for outdoor foliar use

Label changes include:

1. Pollinator Protection Box

2. Directions for Use section contains new pollinator language

Do not apply this product while bees are foraging. Do not apply

this product until flowering is complete and all petals have fallen

unless the following condition has been met.

Secondary routes of neonicotinoid exposure to bees:

residues in plant fluids released by guttation droplets.

Residues in plant fluids released by guttation droplets

Toxicity of guttation water exuded by corn

seedlings grown from Cruiser or Poncho

treated seeds can be near the concentration

applied in field sprays for pest control.

When bees consume guttation drops, they die

within a few minutes (Girolami et al. 2009).

Exposure studies show low likelihood that

bees collect enough guttation fluid from corn

seedlings to affect colony health.

Secondary routes of neonicotinoid exposure to bees:

residues in contaminated water (i.e. spills, irrigation).

Residues in contaminated water (i.e. spills, irrigation)

Neonics have been detected in surface water in the US and Europe.

Water samples collected from 9 stream sites in the Midwest during

the 2013 growing season.

Of the 79 samples documented similar patterns among sites for both

frequency of detection and concentration (median):

clothianidin (75%, 8.2 ppt) > thiamethoxam (47%, <2 ppt) >

imidacloprid (23%, <2 ppt).

Temporal patterns in residues reveal pulses of neonics associated

with rainfall events during crop planting, suggesting seed treatments

as the likely source. (Kolpin and Kuivila 2014)

Secondary routes of neonicotinoid exposure to bees:

treated-seed dusts emitted during sowing, deposited on

off-site flowering vegetation.

Potential route of acute lethal exposure is

contaminated talc exhausted by air planters.

(Girolami et al. 2012; Tapparo et al. 2012; Krupke

et al. 2012)

The majority of the US corn acreage is seed-

treated with neonicotinoid insecticide (i.e. Cruiser

and Poncho).

Seed Treatment Dust Research - Collaborations

Syngenta and Bayer have partnered to assess dust reduction technology.

– New lubricants

– Deflectors

Corn Dust Research Consortium (CDRC)

– Research to aid in developing BMPs

• Dust mitigation

• Flowering vegetation management

• www.pollinator.org/CDRC.htm

Residues in nectar and pollen

represent the major route of

neonicotinoid exposure to bees

Major focus on seed treatments

Residues in nectar, pollen and extrafloral nectaries

- systemic foliar sprays

- soil/seed systemic treatments

- chemigation via drip/overhead irrigation

- residue levels in soil that carryover to flowering plants

- exposure via flowering cover crops or winter annuals

that overlap with seed-treated crops

Crop groups

Neonicotinoid Application Methods

Seed-

treated Soil\at plant

Plant

drench Foliar Chemigation

Cucurbits T I, T, D I, T, D T, D I, T, D

Fruiting vegetables I, D I, D I, T, D I, D

Brassica crops I, T, D I, T, D I, T, D I, T, D

Legume vegetables I, T I I I I

Strawberry I, T T I, T I, T

Berry fruit I, T I, T I, T I

Cranberry I T I

Grape T I, T I, T, D I, T, D

Pome fruit I, T* I

Stone fruit I, T* I

Nut fruit I I I

Citrus T I,T I, T I, T

Sweet corn I, T

Cotton I, T, C I I, D I

Soybean I, T, C I

Canola I, T

Sunflower I, T

Field corn I, T, C

Imidacloprid (I), Thiamethoxam (T), Clothiamidin (C), Dinotefuran (D)

Looking for Neonicotinoids residues…

Setting Application Rate Plant Range (Imidacloprid)

Agricultural Seed coating

at label rate Corn Sunflower Sunflower +1Y Pumpkin Canola

Pollen: 2.1 ppb, up to 18 ppb P: 3 ppb, up to 11 ppb P: 1-2 ppb Non-detectable (thiamethoxam) P: 3 ppb, N: 3.7 ppb (clothianidin)

Bonmatin et al. 2003, 2005a,b. Dively & Kamel 2012. Cutler&Scoott-Dupree 2007

Agricultural Soil drench at label rate Pumpkin P: 30-87 ppb; 52-101 ppb Nectar: 4-12 ppb; 9-14 ppb

Dively & Kamel 2012.

Agricultural Foliar spray at label rate Pumpkin P: 36-147 ppb (dinotefuran) N: 5.3-10.8ppb P: 61-127 ppb (thiamethoxam) N: 6.7-9.1ppb

Dively & Kamel 2012.

Ornamental Soil drench at label rate Rhododendron Amelanchier Cornelian cherry

Blossom: 27-850 ppb (6 months) B: 19ppb (3-6 years) B: 66-4,560 ppb (18 months) Leaves: 56-3,200 ppb (6 months) B: 1,038-2,816 ppb (17 months)

Doering et al. 2004, 2005a,b.

Ornamental Trunk injection

at label rate Horse chestnut B: 5-283ppb (7 days) Maus et al. 2004.

In-Hive Fate of Imidacloprid Residues (Dively et al 2014)

Determine the exposure levels to bees and brood and fate of imidacloprid in colonies

exposed to known levels of residues

Fed SS and PD

(no exposure)

24 colonies were established in new hive boxes, fed sugar syrup (SS) and pollen

diet (PD) to build up populations and then assigned to 3 treatment groups.

Each colony was provisioned with sugar syrup and pollen diet weekly for 6 weeks.

Fed SS (20 ppb) and PD

(nectar exposure)

Fed SS and PD (100 ppb)

(pollen exposure)

Hive samples were collected over time to measure residues of imidacloprid.

Queens were removed after 5 weeks of exposure to trigger queen cells and collect

royal jelly.

Treatment

Samples

taken at

Number of positive detections in 8 colonies

Range of residue levels (ppb)

Bees Beebread

Bee

larvae Honey

Royal

jelly Pollen diet

(100 ppb)

400 g

per week

(40 ug ai)

2 wks

exposure

6

0.2 - 1.4

8

0.5 – 1.7

1

0.4

7

4.7 – 13.4 -

6 wks

exposure

5

0.5 – 1.9

8

0.6 – 1.2

0

ND

7

2.8 - 10.8

8

0.3 – 1.0

6 wks after

exposure

8

0.3 – 0.5

8

0.8 – 1.4

0

ND

8

2.3 – 11.7 - Sugar syrup

(20 ppb)

2000 g

per week

(40 ug ai)

2 wks

exposure

3

0.2 – 0.5

2

0.7 – 1.0

1

0.5

4

0.2 – 3.7 -

6 wks

exposure

0

ND

3

0.2 – 0.9

0

ND

2

0.2 – 0.9

0

ND

6 wks after

exposure

0

ND

2

0.2 – 0.3

0

ND

2

0.2 – 0.5 -

Residues by hive substrate and route of exposure

Treatment

Samples

taken at

Number of positive detections in 8 colonies

Range of residue levels (ppb)

Bees Beebread

Bee

larvae Honey

Royal

jelly

Pollen diet

(100 ppb) Fed 400 g

per week

2 wks

exposure

6

0.2 - 1.4

8

0.5 – 1.7

1

0.4

7

4.7 – 13.4 -

6 wks

exposure

5

0.5 – 1.9

8

0.6 – 1.2

0

ND

7

2.8 - 10.8

8

0.3 – 1.0

6 wks after

exposure

8

0.3 – 0.5

8

0.8 – 1.4

0

ND

8

2.3 – 11.7 - Sugar syrup

(20 ppb)

Fed 2000 g

per week

2 wks

exposure

3

0.2 – 0.5

2

0.7 – 1.0

1

0.5

4

0.2 – 3.7 -

6 wks

exposure

0

ND

3

0.2 – 0.9

0

ND

2

0.2 – 0.9

0

ND

6 wks after

exposure

0

ND

2

0.2 – 0.3

0

ND

2

0.2 – 0.5 -

Positive detections and residue levels were significantly

higher in colonies fed spiked pollen diet

Treatment

Samples

taken at

Number of positive detections in 8 colonies

Range of residue levels (ppb)

Bees Beebread

Bee

larvae Honey

Royal

jelly

Pollen diet (100 ppb)

Fed 400 g

per week

2 wks

exposure

6

0.2 - 1.4

8

0.5 – 1.7

1

0.4

7

4.7 – 13.4 -

6 wks

exposure

5

0.5 – 1.9

8

0.6 – 1.2

0

ND

7

2.8 - 10.8

8

0.3 – 1.0

6 wks after

exposure

8

0.3 – 0.5

8

0.8 – 1.4

0

ND

8

2.3 – 11.7 - Sugar syrup

(20 ppb)

Fed 2000 g

per week

2 wks

exposure

3

0.2 – 0.5

2

0.7 – 1.0

1

0.5

4

0.6 – 3.7 -

6 wks

exposure

0

ND

3

0.2 – 0.9

0

ND

2

0.2 – 0.9

0

ND

6 wks after

exposure

0

ND

2

0.2 – 0.3

0

ND

2

0.2 – 0.5 -

Highest levels in honey followed by lower but consistent levels

in beebread and bees

Treatment

Samples

taken at

Number of positive detections in 8 colonies

Range of residue levels (ppb)

Bees Beebread

Bee

larvae Honey

Royal

jelly

Pollen diet (100 ppb)

Fed 400 g

per week

2 wks

exposure

6

0.2 - 1.4

8

0.5 – 1.7

1

0.4

7

4.7 – 13.4 -

6 wks

exposure

5

0.5 – 1.9

8

0.6 – 1.2

0

ND

7

2.8 - 10.8

8

0.3 – 1.0

6 wks after

exposure

8

0.3 – 0.5

8

0.8 – 1.4

0

ND

8

2.3 – 11.7 - Sugar syrup

(20 ppb)

Fed 2000 g

per week

2 wks

exposure

3

0.2 – 0.5

2

0.7 – 1.0

1

0.5

4

0.6 – 3.7 -

6 wks

exposure

0

ND

3

0.2 – 0.9

0

ND

2

0.2 – 0.9

0

ND

6 wks after

exposure

0

ND

2

0.2 – 0.3

0

ND

2

0.2 – 0.5 -

Residues in larvae were non-detectable, except for several

samples collected at 2 weeks exposure

Treatment

Samples

taken at

Number of positive detections in 8 colonies

Range of residue levels (ppb)

Bees Beebread

Bee

larvae Honey

Royal

jelly

Pollen diet (100 ppb)

Fed 400 g

per week

2 wks

exposure

6

0.2 - 1.4

8

0.5 – 1.7

1

0.4

7

4.7 – 13.4 -

6 wks

exposure

5

0.5 – 1.9

8

0.6 – 1.2

0

ND

7

2.8 - 10.8

8

0.3 – 1.0

6 wks after

exposure

8

0.3 – 0.5

8

0.8 – 1.4

0

ND

8

2.3 – 11.7 - Sugar syrup

(20 ppb)

Fed 2000 g

per week

2 wks

exposure

3

0.2 – 0.5

2

0.7 – 1.0

1

0.5

4

0.6 – 3.7 -

6 wks

exposure

0

ND

3

0.2 – 0.9

0

ND

2

0.2 – 0.9

0

ND

6 wks after

exposure

0

ND

2

0.2 – 0.3

0

ND

2

0.2 – 0.5 -

All royal jelly samples from colonies fed 100 ppb had detectable

imidacloprid residues, averaging 0.6 ppb, whereas residues in royal

jelly were non-detectable in the sugar syrup group

Implications to Bee Exposure

Residues in the hive can be several orders of magnitude lower

than levels in contaminated pollen and nectar entering colonies.

Imidacloprid degrades rapidly in the honey bee (half-life of 4-5

hours) and can be further diluted by uncontaminated nectar and

pollen entering the colony.

Residues in bees, larvae and beebread were below the low no-

effect concentration of 20 ppb for sublethal effects.

At 100 ppb exposure, residues in honey exceeded the dietary

doses causing sublethal effects and represent a significant portion of

the dietary LD50.

Royal jelly residues averaged 0.6 ppb in colonies fed 100 ppb;

which is likely to have sublethal effects on queen heath.

GOOD

NEWS

BAD

NEWS

Results of field colony studies on neonic effects:

Most studies found no detrimental effects on colonies placed during

flowering in fields or tunnel cages of canola and corn seed-treated with

neonics.

One study in Europe investigated the colony health of 16 apiaries

surrounded by variable land use of imidacloprid seed-treated corn

fields. They reported a negative correlation between colony mortality

rate and the acreage of treated fields, suggesting imidacloprid had no

adverse effect on colony health.

A recent study (Sandrock et al. 2014) reported that sublethal dietary

exposure to thiamethoxam and clothianidin had significant negative

short-term and long-term effects on colony performance and queen

health.

Chronic Sublethal Effects of Prolonged Exposure to Imidacloprid

on Honey Bee Colony Health (Dively et al 2014)

Control – 0 ppb

Whole colony experiment repeated in each of two years

Colonies were started in new hive boxes, fed sugar syrup to build up

populations, equalized and then assigned to 4 treatment groups.

5 ppb

Low exposure

Each group consisted of 7 or 10 replicate colonies.

Colonies were then exposed to imidacloprid residues in supplemental pollen

diet provisioned weekly for 12 weeks.

20 ppb 100 ppb

High exposure

GOOD

NEWS Imidacloprid doses up to 100 ppb had no effects on

foraging activity or colony health during and shortly

after 12 weeks of exposure.

Diseases and pest species did not affect colony

health and were not related to dose.

Most likely encountered field exposure doses of 5

ppb in seed-treated crops had no significant effects

on honey bee colony health.

Implications to Honey Bee Colony Health

BAD

NEWS Honey stores indicated that exposed colonies may

have avoided the contaminated food.

Chronic effects of 20 and 100 ppb were delayed

later in the summer, when colonies experienced

higher rates of queen failure and broodless

periods, which led to reduced overwintering

success.

Represent worse-case scenarios of dietary

exposure…uncommon for honey bees to be

exposed to these doses for extended periods.

Implications to Honey Bee Colony Health

Neonicotinoids and Colony Health – they are involved

Probably affect colony health at higher and prolonged sublethal

exposure doses but not at field realistic doses associated with seed-

treated crops.

May interact with pathogens to cause colony stress.

Weight of evidence indicates that neonicotinoids are not the major

causal factor causing honey bee losses.

No temporal and spatial relationships with neonicotinoid use.

Very few hive samples contain neonicotinoids.

Imidacloprid and other neonics degrade very rapidly in the hive.

No pattern of neonic exposure associated with colony losses.

No evidence of gene expression linked to pesticide stress.

Certain applications should be restricted (chemigated treatments,

ornamental plant drenches, tree injections).

Multiple stress factors affecting honey bee health

Scientists are focusing on the interaction of factors:

– Parasites (Varroa mites)

– Diseases (Nosema, bacteria, viruses)

– Poor bee nutrition

• Lack of varied diet

• Lack of suitable habitats

– Beekeeping management stresses

– Pesticides (used in hives as well as in agriculture)

– Weather patterns and changing climate

– Lack of genetic diversity leads to weakened resistance to pests and diseases

– Queen failure

How can farmers and applicators reduce risks to honey bees from

pesticide applications?

Carefully follow label precautions with regard to bee safety.

Do not treat fields in bloom or when bees are foraging.

Apply insecticides in the late evening, night, or early morning when

fewer bees are foraging and after flowers close for the day.

Use non-systemic, short-residual products if possible when treating

during flowering.

Communicate with beekeepers and be aware of bee hive locations

before applying insecticides.

If colonies are present, contact beekeepers in time for them to protect

or move colonies.

Establish bee forage plants in wild or uncultivated areas to reduce bee

dependence on crop plants.

Use neonic-seed treatments only when necessary, lower doses,

improved seed lubricants to minimize abrasion, and deflectors.

Still Lots of Knowledge Gaps

Thank you …. Questions

Thanks to the USDA-ARS Bee Lab and EPA for funding