Visit to Chitwan, NepalVisit to Chitwan, NepalFebruary 24-27, 2010February 24-27, 2010

Protocol to detect and Protocol to detect and

assess pollination deficit in assess pollination deficit in

crops in Nepalese sitescrops in Nepalese sites

Bernard E. Vaissière (INRA, Avignon, France)

Breno M. Freitas (U. de Ceará, Fortaleza, Brazil)

Barbara Gemmill-Herren (FAO, Rome, Italy)1

Background : How to detect and Background : How to detect and assess pollination deficit in crops ?assess pollination deficit in crops ?

2008 : Literature review

January - March =>

- Database: 67 publications that dealt with pollination deficit in crops

- Preliminary draft of the review

=> Expert workshop in Avignon on April 3-6, 2008

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Pollination deficit : Pollination deficit : definition and conceptdefinition and concept

=> Pollination deficitBased on Wilcock & Neiland (2002) who defined the concept of pollination failure

Pollination deficit refers to quantitative or qualitative deficit of pollination which decreases the sexual reproductive output of plants

Other terminology • Pollination limitation (used by Ashman et al. 2004, Knight et

al. 2005) => refers to the absence of pollen deposition

• Pollen limitation => refers to an inappropriate or insufficient

deposition of pollen on the stigma3

Working definition of pollination Working definition of pollination deficit in cropsdeficit in crops

Crop pollination deficit refers to inadequate

pollen receipt that limits agricultural output

Limitation of agricultural output• Quantitative or qualitative

• Productivity

• Sustainability

Inadequate pollen receipt• Quantitative

• Qualitative (self-incompatible species)

• Timing (effective pollination period / stigmatic receptivity)

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Pollination deficit definition and Pollination deficit definition and conceptsconcepts

Currentlevel

Optimumlevel

=> How to define and reach the optimum?

Pollination deficit

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Methods to reach better or optimal Methods to reach better or optimal pollination in cropspollination in crops

• Yield / yield components [fruit set & seed set]

• Fruit quality (size ; aspect)

• Seed quality (seed germination rate; oil content)

• Earliness and uniformity of output

• Market value / profitability

• Environmental & societal impacts

Optimum pollination => Maximum output given the current available resources and taking into account the production objectives

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1. Pollen production & viability

2. Transport and deposition:

Quantitative pollination: # of visits received / flower

=> Lack of visits (population effect)

(yield of Coffea arabica increased with the introduction of

Africanized honeybees in Central America ; Roubik 2002)

Causes of pollination deficitCauses of pollination deficit

Qualitative pollination: quality, distribution, origin of pollen

- Lack of wild bees with high pollination effectiveness

- Lack of wild bees for pPositive interaction with honey bees

- Low pollinator biodiversity => lower and less stable pollination

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Methods to reach better or optimal Methods to reach better or optimal pollination in cropspollination in crops

Improved pollination

≈

Improved pollen transport,

deposition & fertilization

effectiveness (viability, compatibility)

8

Consensus methods to reach better or Consensus methods to reach better or optimal crop pollinationoptimal crop pollination

Treatment :

Introduce colonies of honey bees (Apis cerana and/or

Apis mellifera) in or nearby the treated study fields at the

onset of effective flowering (e.g. flowering of production

trees in apple orchards) to increase density of honey bees

on flowers of study fields while the control fields will not

be provided with additional honey bee colonies

1. Supplementation with honey bee colonies (apple, buckwheat, cucurbits, mustard)

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Supplementation with honey bees - 2

• Pollination depends upon pollinator species introduced;

• Limited to managed pollinators (Apis cerana or A. mellifera);

• Unclear relationship between introduced bees and forager density;

• Effect of pollinator addition is probably not additive in relation to existing pollinator population;

• Possible negative effects of high pollinator densities (e.g. bumble bees)

+

–

More realistic than hand pollination for most species Applicable in farmer production managementEasy practice in many circumstances, even around houses for subsistence crops

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Experimental design

1. In homogeneous geographical area (≈ similar altitude and distance to semi-natural habitat), select ten fields : 5 fields with and 5 fields without colonies added (completely randomized design)

Supplementation with honey bees – 3

2. Use the geographical area (for example the altitude) as blocking factor and select five pairs of fields, each subset of pairs in an homogeneous area, with one field with and one field without colonies added (randomized complete block design)

or

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or

3. In large fields > 450 m long away from one side where colonies can be introduced, select five such fields and test for a gradient of pollinator density from near to far from side with colonies (pollinator front) by recording data at 20, 220 and 420 m away from colonies 11

Special requirements

Supplementation with honey bees – 4

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• Record pollinator density & diversity just prior to colony introduction to know baseline situation, that is the abundance and diversity of the local pollinator population at onset of flowering;

• Colonies should be introduced at night or late evening or very early morning so as to keep all their foraging force for their new location;

• The stocking rate (number of introduced colonies per ha of target crop) should be based upon existing practices, but also take into account the area of flowering target crop without colony provided in the surroundings (as a rule of thumb, the smaller the study field, the higher the stocking rate should be and it is best not to go below the introduction of 2 colonies along any study field to compensate for the possible death of one colony following its introduction)

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• Minimum distance between adjacent fields should be ≥ flight distance of most pollinator species (≈ ≥ 2 km for honey bees);

Consensus methods to reach better or Consensus methods to reach better or optimal crop pollinationoptimal crop pollination

2. Proximity to semi-natural habitats (large cardamom)

Semi-natural habitat ≈ CORINE level 1 : forest, natural grassland, brush,…

Treatment :

Use the landscape context, in particular the proximity of

the treated fields to large patches (> 0.5 ha) of semi-

natural habitats to increase pollinator abundance &

biodiversity in the flowers of the study fields while

control fields will be selected away from semi-natural

habitats (≥ 500 m)

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Proximity to semi-natural habitats - 2

• Realistic variations of pollinator abundance & diversity

• Contrasting situations can be achieved

• Takes into account all the pollinator fauna, including

species not commercially raised

+

–

• Potential correlated factors that affect yield components can

confound results (e.g. fields along forest on steep slope may

have inferior soil & overall agronomic conditions than faraway

fields in the valley)

• Requires landscape heterogeneity

• Large changes in pollinator community possible from year

to year 14

Experimental design

1. In homogeneous geographical area (≈ similar altitude and distance to semi-natural habitat), select ten fields : 5 fields adjacent to and 5 fields away from semi-natural habitats (completely randomized design)

2. In mountainous areas, use the geographical area (e.g. the altitude) as blocking factor and select five pairs of fields overall, with each subset of pairs in an homogeneous area, and each field from a pair adjacent to and the other set afar from semi-natural habitats (randomized complete block design)

or

3. In large fields > 450 m long away from side close to semi-natural habitats are available, select five such fields and test for a gradient of pollinator density and diversity by recording data at 20, 220 and 420 m away from side with semi-natural habitats (pollinator front)

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or

Proximity to semi-natural habitats - 3

• Area of semi-natural habitat adjacent to field should be as large as possible so as to provide as diverse and abundant a pollinator fauna as possible. For small bees, area ≥ 0.5 ha; for large bees => larger fragment;

Proximity to semi-natural habitats - 4

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Special requirements

• Minimum distance between adjacent fields should be ≥ flight distance of most pollinator species (≈ ≥ 2 km for honey bees);

• Record distance to and type of closest semi-natural habitats for all fields;

• If at all possible with GIS data available, determine proportion of semi -natural habitats around each study fields within a 1 km radius;

Fixed-effect factors or independent Fixed-effect factors or independent variable (distance)variable (distance)

• Presence or absence of nearby honey bee colonies;

or

• Close or far from semi-natural habitats;

or

• When gradient is possible, distance to pollinator front (introduced colonies or closest semi-natural habitat)

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Possible blocking factors for Possible blocking factors for experimental design with paired experimental design with paired

fieldsfields

• Altitude (valley versus hill top ; e.g., mustard);

• Distance to forest front (blocking factor if treatment is introduction of honey bee colonies ; e.g., apples);

• Variety and planting pattern (e.g., apples with production and pollenizer varieties);

• Village (e.g., possibly cucurbits)

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Dependent variables to be recordedDependent variables to be recorded

Forager density (forager/floral unit)

• Pollinators/100 floral units (instantaneous counts)

Forager diversity (species richness) • Pollinator catch on transects (with sweep

nets)

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Pollinator activity should be recorded under good weather Pollinator activity should be recorded under good weather

conditions for foraging : T ≥ 12°C, vegetation dry, light windconditions for foraging : T ≥ 12°C, vegetation dry, light wind

Possible co-variables to be recordedPossible co-variables to be recorded

• Flower density at each recording of pollinator activity ;

• Temperature & relative humidity at each

recording of pollinator activity ;

• Schedule of pesticide applications in relation

to flowering;

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10 mminimum

45 m minimum

25 m

70 mminimum

50 m

If size of study field permits (≥ 0.3 ha) => set experimental site of 50 m x 25 m aligned along rows if present

row of crop

10 mminimum

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Layout to measure pollinator abundance & Layout to measure pollinator abundance & diversity when experimental site presentdiversity when experimental site present

[optional recordings in brackets][optional recordings in brackets]

1

2 4

5

6

3

Net captures : Subunit n° j of a fixed transect consisting of six 25-m long subunits for insects capture over a 2-m width for 5 min in each sub-unit

j

1

2

3

4Instantaneous count of potential pollinators (100 floral units scanned for pollinators in plot n° i)

i

[Plot to record the number of open flowers [in 1 m2 quadrant (buckwheat, mustard)]

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50 m

25 m

0

17

34

50

25 20 15 10 5 0

For smaller fields or fields with special shapes, For smaller fields or fields with special shapes, the the experimental site is the whole fieldexperimental site is the whole field

[optional recordings in brackets][optional recordings in brackets]

5

4 2

1

6

3

Net captures : Subunit n° j of a fixed transect consisting of six 25-m long subunits for insects capture over a 2-m width for 5 min in each sub-unit. If the perimeter of the field is < 150 m, it is OK to go back onto an area already sampled.

j

1

23

4

Instantaneous count of potential pollinators (100 floral units scanned for pollinators in plot n° i; these flowers can be recorded on the side of the field to avoid trempling ofthe crop

i

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[Plot to record the number of open flowers [in 1 m2 quadrant (buckwheat, mustard)]. These quadrats are set at a fixe spot nearby the start of a subunit to record pollinator diversity

For very large study fields, the experimental site

is set half way between the center and the border

d

d

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Experimental designExperimental design

The management of all experimental

units is assumed to be as similar as

possible except for the pollinator

treatment

Same variety !

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Assessing agronomic & economic yieldAssessing agronomic & economic yield• • Plants can compensate for pollen limitation with longer Plants can compensate for pollen limitation with longer

flowering periods, more flowers, etc...flowering periods, more flowers, etc...

• • Fruit set and/or seed set can be ressource-limitedFruit set and/or seed set can be ressource-limited

Pollination treatments done on a plant-wide basisPollination treatments done on a plant-wide basis,

that is with the whole plant as experimental unit

(Knight TM et al. 2005. Pollen limitation of plant reproduction: pattern and processes. Annu. Rev. Ecol. Evol. Syst. 36 :467-497)

Dependent end variablesDependent end variables

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Dependent variablesDependent variables

Yield (agronomic terms : unit weight/unit area)

• Straightforward (per plant or per plot)• Linked to commercial yield• Meaningful variable for farmers & consumers• Dependent of agronomic situation

• Long lag time until result• Between field variability can confound the link to pollination

deficit (water availability; fertilizer; pest control)• Data access may be difficult (harvesting before the farmer)• Undeterminate crops may require repeated harvesting over

the season

+

–

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Dependent variablesDependent variables

Yield (monetary terms : market value)

• Very context specific• May be very volatile• Lack of accepted methodology (interdisciplinary)• Link to pollination deficit may be tenuous & difficilut to

establish• May be beyond the control of individual farmers

• Meaningful variable for farmers & consumers• Meaningful for government & policy makers• May assist farmers with proper documentation• Can include other currency of value for society (e.g.,

nutritional value)

+

–

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Experimental unitsExperimental units

Individual plant or tree (e.g., apple, mustard in mixed plantings, cucurbits)

• Yield unit

• Biological unit

• Considerable work if using hand pollination or if

dependent variable is fruit/seed set with many flowers

• Does not control for ressource allocation between

years except if recorded over several years

+

–

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Experimental unitsExperimental units

Plot / field (e.g., buckwheat, cucurbit)

• Does not control for ressource allocation between years

except if recorded over several years

(• Confound other inputs)

• When individual plant not possible (buckwheat, rape)

• Yield unit => talk to farmer

• can be related to economic unit

+

–

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Layout of the yield plots when experimental Layout of the yield plots when experimental site presentsite present

1

2

3

4

Instantaneous count of potential pollinatorsi

Plot to record the number of open flowers

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50 m

25 m

0

17

34

50

25 20 15 10 5 0

Yield plot (length of row – usually 2 m – or

area of 1 m2 – as for buckwheat – or harvest

individually 5 adjacent plants – as in mixed

planting of mustard – or 2 trees adjacent and

far away from pollenizer tree – as in apple)

Layout of the yield plots in smaller fields or Layout of the yield plots in smaller fields or fields with special shape fields with special shape where the experimental where the experimental

site is the whole fieldsite is the whole field

1

Instantaneous count of potential pollinators

2

3

4

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Plot to record the number of open flowers

l 4l/5 3l/5 2l/5 l/5 0

width l

LengthL

0

L/5

3L/5

L

2L/5

4L/5 Yield plot (length of row – usually 2 m – or

area of 1 m2 – as for buckwheat – or harvest

individually 5 adjacent plants – as in mixed

planting of mustard)

Summary of protocol to detect & Summary of protocol to detect & assess pollination deficit in cropsassess pollination deficit in crops

Method to expect better pollination• Supplement local pollinator population with honey

bees• Proximity to semi-natural habitats

Variables to record • Pollinator density (forager/floral unit at the right

time) • Pollinator diversity (even in coarse categories)

Experimental unit• field or plot or plant

Final dependent variables• Agronomic yield & monetary yield

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