# Tree diversity improves forest resistance to insect defoliators

Virginie Guyot, Marc Deconchat, Aude Vialatte, Bastien Castagneyrol, Herve Jactel

► To cite this version:

Virginie Guyot, Marc Deconchat, Aude Vialatte, Bastien Castagneyrol, Herve Jactel. Tree diversity improves forest resistance to insect defoliators. IUFRO Conference, Sep 2015, Sopot, Poland. 25 p. hal-01608084

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# Tree diversity improves forest resistance to insect defoliators

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Inge van Halder

Virginie Guyot, Marc Deconchat, Aude Vialatte (INRA Dynafor, Toulouse)

Bastien Castagneyrol, Hervé Jactel (INRA Biogeco, Bordeaux)

Population Dynamics and Integrated Control of Forest Defoliating Insects
IUFRO Conference - Sopot - September 28 - October 2, 2015
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# Planted forest health: The need for a global strategy

M. J. Wingfield,¹* E. G. Brockerhoff,² B. D. Wingfield,¹ B. Slippers¹

21 AUGUST 2015 • VOL 349 ISSUE 6250

<table><thead><tr><th>TOOLS FOR DEALING WITH FOREST PESTS</th><th>POTENTIAL GLOBAL IMPACT*</th></tr></thead><tbody><tr><td>Pest research tools</td><td></td></tr><tr><td>Pest risk assessment</td><td></td></tr><tr><td>Pest information database</td><td></td></tr><tr><td>Pathway risk management</td><td></td></tr><tr><td>National quarantine</td><td></td></tr><tr><td>Surveillance tools</td><td></td></tr><tr><td>Incursion response/eradication</td><td></td></tr><tr><td>Biological control</td><td></td></tr><tr><td>Genetic resources/breeding</td><td></td></tr><tr><td>Genetic engineering</td><td></td></tr></tbody></table>

*Yellow = low; Orange = medium; Red = high
# Classical Biological Control

*Introduction of natural enemies*

in order to control pest insects (most often exotic)

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ELSEVIER

Available online at www.sciencedirect.com

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ScienceDirect

Biological Control 45 (2008) 172-175

Biological
Control

www.ebsvier.com/locallybcom

## Recent advances in conservation biological control of arthropods by arthropods

Mattias Jonsson<sup>a,*</sup>, Steve D. Wratten<sup>a</sup>, Doug A. Landis<sup>b</sup>, Geoff M. Gurr<sup>c</sup>

# Conservation Biological Control

*Manipulating the environment* in order to enhance natural processes of biotic regulation

- bottom up = interactions insects – non host plants

- top down = interactions insects – native natural enemies

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**Manipulation through change of forest composition**
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## Associational resistance

## LETTER

# Tree diversity reduces herbivory by forest insects

Hervé Jactel¹* and Eckehard G. Brockerhoff²

¹INRA, UMR1202 Biodiversity, Genes & Communities,

## Abstract

Biodiversity loss from plant communities is often acknowledged to affect primary production but little is known about effects on herbivores. We conducted a meta-analysis of a worldwide data set of 119 studies to compare herbivory in single-species and mixed forests. This showed a significant reduction of herbivory in more diverse

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- 42%

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- 15%

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0%
# Associational resistance in forests

## Limits:

- tested in experimental conditions

- on young trees

- comparisons pure vs. mixed stands (no gradient of diversity)

- focus on particular pest species, mostly native

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Oikos 000: 001–012, 2015

doi: 10.1111/oik.02090

© 2015 The Authors. Oikos © 2015 Nordic Society Oikos

Subject Editor: Ulrich Brose. Editor-in-Chief: Christopher Lortie. Accepted 5 March 2015

Contrasting effects of tree diversity on young tree growth and resistance to insect herbivores across three biodiversity experiments

Josephine Haase, Bastien Castagneyrol, J. Hans C. Cornelissen, Jaboury Ghazoul, Jens Kattge, Julia Koricheva, Michael Scherer-Lorenzen, Simon Morath and Hervé Jactel

→ Lack of global pattern
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ELSEVIER

Contents lists available at ScienceDirect

Perspectives in Plant Ecology, Evolution and Systematics

Journal homepage: www.elsevier.com/locate/ppees

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Forum

A novel comparative research platform designed to determine the
functional significance of tree species diversity in European forests

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CrossMark

6 exploratory sites in
Mediterranean, temperate and boreal forests

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Main European tree species

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# Effects of forest diversity on tree defoliation by insects

Defoliation

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214 forest plots
13 609 trees

3 trees observed/species

1 670 sampled trees
# Effects of forest diversity on defoliation

## on leaves

60 - 100/tree = 81 908 leaves

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## on tree crowns

ICP Forest protocol
= 1670 trees

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mean % crown defoliation

R² = 0.57

***

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mean % leaf area removed by chewers

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Effects of forest diversity on defoliation

Mean % of crown defoliation (± SE)

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Global Ecology and Biogeography, (Global Ecol. Biogeogr.) (2015)

Global patterns in background losses of woody plant foliage to insects

Mikhail V. Kozlov*, Vojtěch Lanta¹, Vitali Zverev and Elena L. Zvereva

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Effects of forest diversity on defoliation in broadleaves

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11 broadleaves species

$$F_{1,328} = 16.01, P < 0.001$$

Associational
resistance

9.6% monocultures

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6.6% in mixtures of 5 spp.

large variability
# Effects of forest diversity on defoliation in broadleaves

defoliation

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* Carpinus betulus
* Castanea sativa
* Quercus robur - petraea
* Quercus faginea
* Fagus sylvatica
* Fraxinus excelsior
* Acer pseudoplatanus
* Quercus cerris
* Betula pendula
* Quercus ilex
* Ostrya carpinifolia

* AR
* AS

* significant

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temperature

Italy
Spain
Germany
Poland
Romania
Finland

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temperature
# Effects of forest diversity on defoliation in broadleaves

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defoliation

## Majority of broadleaved tree species with AR

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* significant

No effect of latitude

°C

temperature
<figure><img src="image_33.png" /><figcaption>Asian chestnut gall wasp
ACGW</figcaption></figure>

*Dryocosmus kuriphilus*
A focus on chestnut forests in Italy

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→ 80%

Agricultural and Forest Entomology (2013), DOI: 10.1111/afb.12036

# Invasion by the chestnut gall wasp in Italy causes significant yield loss in *Castanea sativa* nut production

Andrea Battisti*, Isadora Benvegnù*†, Fernanda Colombari* and Robert A. Haack‡
Effect of tree diversity on resistance to ACGW

100% chestnuts damaged

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Tree species richness

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Associational
resistance
(-50%)

**Citation:** Guyot V, Castagneyrol B, Vialatte A, Deconchat M, Selvi F, Bussotti F, et al. (2015) Tree Diversity Limits the Impact of an Invasive Forest Pest. PLoS ONE 10(9): e0136469. doi:10.1371/journal.
Mean % defoliation per plot

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Tree apparenty
# Conclusions

*Global pattern of associational resistance in European forests*
= lower defoliation in mixed forests

1. large array of 11 main broadleaved species

2. in mature forests

3. irrespective of the insect species

4. incl. alien invasive pest

5. across tree diversity gradient (≠ pure vs. mixed)

6. crown defoliation = relevant to forest productivity
# Conclusions

*Mechanisms remain to be addressed*

1. Diversity causes *resource dilution*

* reduced abundance of host trees

2. Diversity reduces *“host apparenty”*

* reduced physical detectability of host

* interference with host finding by non-host odours

3. Diversity enhances *activity of natural enemies* of pests

* more insect predators, parasitoids, insectivorous birds
# Conclusions

2 avenues for implementation in forestry

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1. Heterospecific hedgerows

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2. Two-species plantations

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Thank you for attention !

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Inge van Halder
defoliation

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* Effet significatif

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SA in
Broadleaved-
Broadleaved

RA in
Broadleaved -
Conifers
Broadleaved, plots BC

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(F<sub>1,160</sub> = 12.06, P < 0.001)

Broadleaved, plots BB

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(F<sub>1,201</sub> = 4.06, P = 0.045)

BB ou CC

BC ou CB

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defoliation

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AR in oaks

AS in pioneer species

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temperature

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SLA

$$y = 0,0227x - 0,4874$$

$$R^2 = 0,445$$

$$P = 0.035$$