Impact of host composition and shade tree spatial structure on pest infestation in cocoa agroforests

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Impact of host composition and shade tree spatial structure on pest infestation in cocoa agroforests

Cynthia Gidoin

gidoin@supagro.inra.fr

UR 106

Marie Ange Ngo Bieng, Christian Cilas, Régis Babin, Martijn ten Hoopen, Leila Bagny Beilhe

18 August 2013

the 11th INTECOL Congress.

Montpellier France Yaoundé, Cameroon

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Ecosystem services Multispecies agroecosystems

Avelino et al. 2011 ; Ratnadass et al., 2012 ; Maleizeux et al., 2008

2

(3)

Cacao agroforests

Ecosystem services Multispecies agroecosystems

Complex

vegetation structure

3

(4)

Cacao agroforests

Ecosystem services Multispecies agroecosystems

Complex

vegetation structure ?

4

(5)

Cacao agroforests

Ecosystem services Multispecies agroecosystems

Complex

vegetation structure ?

Pest

5

(6)

Cacao agroforests

Pest Mirids S. singularis

Chocolate

Pod cacao Complex

vegetation structure Crop

Ploetz 2007 ; Babin 2009

6

(7)

Ligneous Vertical structure

Horizontal structure

Multi strata Not regular

Crop

Cacao agroforests S. singularis

Pod cacao

Chocolate

Malezieux et al., 2008 ; Schroth et al., 2004; Ploetz 2007 ; Babin 2009

7

Pest

Mirids

(8)

Pod

Microclimate Resource

Vertical structure

Horizontal structure

Crop

Cacao agroforests S. singularis

Shade

- -

-

Malezieux et al., 2008 ; Schroth et al., 2004; Ploetz 2007 ; Babin 2009

8

Pest Mirids

Ligneous spatial structure

(9)

Microclimate Resource

Vertical structure

Horizontal structure

Cacao agroforests S. singularis

Shade

- -

Host composition

Pod

Crop -

-

Abundance Density

Host composition

Stephens et al. 2012 ; Malezieux et al., 2008 ; Schroth et al., 2004; Ploetz 2007 ; Babin 2009

9

Pest Mirids

Ligneous spatial structure

(10)

Microclimate Resource

Vertical structure

Horizontal structure

Cacao agroforests S. singularis

Shade

- -

Host composition

Pod

Crop -

-

Abundance Density

Host composition

Alternative host Cola spp.

+ +

Stephens et al. 2012 ; Malezieux et al., 2008 ; Schroth et al., 2004; Ploetz 2007 ; Babin 2009

10

Pest Mirids

Ligneous spatial structure

(11)

Microclimate Resource

Vertical structure

Horizontal structure

Cacao agroforests S. singularis

Shade

- -

Host composition

Pod

Crop -

-

Abundance Density

Host composition

Alternative host Cola spp.

+ +

1- What are the independent effects and relative importance of host composition and shade tree spatial structure in mirid density at the plot scale ?

2- What is the vegetation structure of agroforest to promote in order to reduce the mirid density at the plot scale.

Ligneous spatial structure

11

Pest

Mirids

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Yaoundé Obala Centre

7m

Sampling unit: 50 x 50 m Plot (x 20)

Cacao Fruit tree

Forest tree

Dcov %Fo HSfo HSfu

Plant spatial structure

Cacao agroforests

12

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Dcov %Fo HSfo HSfu 7m

Plot (x 20)

Cacao Fruit tree

Aggregated Random Low density

Forest trees (HSfo)

Fruit trees (HSfu)

Low density/Random/Regular

Ripley’s function Typology

Sampling unit: 50 x 50 m

Forest tree

Plant spatial structure

Cacao agroforests

Ripley 1977 ; Ngo Bieng et al., 2013

13

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Dcov %Fo HSfo HSfu Plot (x 20)

Cacao

_≈ 7 m

Cacao tree abundance Cacao tree density

Cola spp. Density Production

Cola spp.

Plant spatial structure

Cacao agroforests

Host composition

Abca Dca Dcola Prod

14

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Plot (x 20)

Cacao Mirid density Cola spp.

x 80 2011 and 2012

Cacao tree abundance Cacao tree density

Cola spp. Density Production

Cacao agroforests

Plant spatial structure Host composition

Abca Dca Dcola Prod

15

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Mirid density

Hierarchical partitionning

More causal factor explaining mirid density ?

Y ~ Xi Ri : total variance explained Ri = Ii + Ji

I : Independent contribution J : Joint contribution

Xi collinearity

Y

X i : Host composition

Abca Dca Dcola Prod Dcov %Fo HSfo HSfu

Plant spatial structure

Mac Nally 2000

16

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56.38 %

Hierarchical partitionning

15

10

5

0

13.9%

Plant spatial structure Mirid density

% variance explained

21 % 79 %

Host composition

49%

12.0%

Independent Joint

Abca Dca Dcola Prod

17

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56.38 % 12.0%

13.4%

Hierarchical partitionning

-

Mirid density

Plant spatial structure

R² = 0.22

Plant spatial structure Vertical structure

%Fo

Log(Dmir)

0

0 %Fo 100

F = 10.8**

4 2

Forest rather than fruit trees

18

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Forest rather

than fruit trees

^{56.38 %}

12.0%

13.4%

Hierarchical partitionning

Plant spatial structure

R² = 0.22

Plant spatial structure Vertical structure

Horizontal structure

%Fo

HSfo

ab b

3,5 2,7 2,1

a

Log(Dmir)Log(Dmir)

0

0 %Fo 100

F = 10.8**

4 2

Mirid density

F = 3.9* Random rather than

aggregated

R²= 0.17

-

19

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Hierarchical partitionning

R² = 0.22

Plant spatial structure Vertical structure

Horizontal structure

%Fo

HSfo

ab b

3,5 2,7 2,1

a

R²= 0.17

Log(Dmir)

F = 3.9*

Log(Dmir)

0

0 %Fo 100

F = 10.8**

4 2

Babin et al., 2010

- Homogeneous shade Forest rather

than fruit trees

Random rather than

aggregated

20

%trans.

light

Mirid/

cacao

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Hierarchical partitionning

R² = 0.22

Plant spatial structure Vertical structure

Horizontal structure

%Fo

HSfo

ab b

3,5 2,7 2,1

a

Log(Dmir)Log(Dmir)

0

0 %Fo 100

F = 10.8**

4 2

- Homogeneous shade

Architectural characteristics

Our data

Babin, 2009

R²= 0.17

F = 3.9*

Forest rather than fruit trees

Random rather than

aggregated

Fu

Fo

20

Crown height(m) 5

21

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Hierarchical partitionning

R² = 0.22

Plant spatial structure Vertical structure

Horizontal structure

%Fo

HSfo

ab b

3,5 2,7 2,1

a

Log(Dmir)Log(Dmir)

0

0 %Fo 100

F = 10.8**

4 2

- Homogeneous shade

% light variance reduction

Martens, 2009

40%

3 16

80%

Canopy cover

R²= 0.17

F = 3.9*

Forest rather than fruit trees

Random rather than

aggregated

Architectural characteristics

Our data

Babin, 2009

Fu

Fo

20

Crown height(m) 5

PAR variance (.106 ) 22

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Host composition Microclimate

Mirids pest

Ligneous spatial structure

Resource

Vertical structure

Horizontal structure

Crop

Abundance Density

Amount

cacao Shade

-

Alternative host Cola spp.

Forest rather than fruit trees

Random rather than aggregated

79%

21%

Conclusion

Significance of the study: Mirid density is more explained by shade tree spatial structure than by host composition. Promoting forest trees randomly distributed.

23

Pod

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Host composition Microclimate

Mirids pest

Ligneous spatial structure

Resource

Vertical structure

Horizontal structure

Crop

Abundance Density

Pod

Amount

cacao Shade

-

Alternative host Cola spp.

Forest rather than fruit trees

Random rather than aggregated

79%

21%

Conclusion

Natural ennemies Ants ?

Flushes

New questions:

-

Why shade reduce mirid density while it promote larvae development ? -

-

24

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Host composition Microclimate

Mirids pest

Ligneous spatial structure

Resource

Vertical structure

Horizontal structure

Crop

Abundance Density

Pod

Amount

cacao Shade

-

Alternative host Cola spp.

Forest rather than fruit trees

Random rather than aggregated

79%

21%

Conclusion

Natural ennemies Ants ?

New questions:

-

Why shade reduces mirid density while it promotes larvae development ?

-

What are the independent effects of host composition and shade tree spatial structure in black pod attack intensity at the plot scale ?

Black pod disease +

Flushes -

25

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Acknowledgements

Marie Ange Ngo Bieng Régis Babin

Leïla Bangny Beilhe Christian Cilas

Martijn ten Hoopen

Literature cited

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Babin, R. 2009. Contribution à l’amélioration de la lutte contre le miride du cacaoyer

Sahlbergella singularis Hagl. (Hemiptera : Miridae). Influence des facteurs agro-écologiques sur la dynamique des populations du ravageur. Thesis. University III, Montpellier, France.

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Malezieux, E., Crozat, Y., Dupraz, C., Laurans, M., Makowski, D., Ozier-Lafontaine, H., et al. 2009.

Mixing plant species in cropping systems: concepts, tools and models. A review. Agronomy for Sustainable Development 29:43–62

Mac Nally, R. 2000. Regression and model-building in conservation biology, biogeography and ecology: The distinction between and reconciliation of “predictive” and “explanatory” models.

Biodiversity and Conservation, 9: 655–671

Martens, S. N., Breshears, D. D., & Meyer, C. W. 2000. Spatial distributions of understory light along the grassland/forest continuum: effects of cover, height, and spatial pattern of tree

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Ngo Bieng, M. A., Gidoin, C., Avelino, J., Cilas, C., Deheuvels, O., and Wery, J. 2013. Diversity and spatial clustering of shade trees affect cacao yield and pathogen pressure in Costa Rican agroforests. Basic and Applied Ecology 14:329–336

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Cacao agroforests

Plant spatial structure

Dcov %Fo HSfo HSfu Plot (x 20)

Cacao Mirid density Cola spp.

x 80

2011 and 2012

Host composition

Abca Dca Dcola Prod

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Cacao agroforests

What are the relative contributions of host composition,

and plant associated spatial structure in mirid infestation at the plot scale ?

Plant spatial structure

Dcov %Fo HSfo HSfu 7m

Plot (x 20)

Cacao Fruit tree

Forest trees (HSfo)

Fruit trees (HSfu)

Low density/Aggregated/Random/Regular

Regular

Ripley’s function Typology

Forest tree

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Gidoin, C., Avelino, J., Deheuvels, O., Cilas, C. and Ngo Bieng, MA. submitted to Phytopathology.

Shade tree spatial structure and pod production explain Frosty Pod Rot intensity in cacao agroforests, Costa Rica.