1. The study examined the impacts of predator diversity and biomass on biocontrol services against pollen beetle pest in winter oilseed rape crops. 2. Experiments showed that increased predator diversity and biomass reduced pest survival, but biomass effects played a greater role than diversity effects. 3. Certain carabid beetle monocultures and mixtures provided greater biocontrol than others due to predatory facilitation or behavioral interference between species. Increased predator biomass generally corresponded to greater reductions in pest survival across treatments.

1. The impacts of bioenergy crop production on
carabids and associated biocontrol services.
O’Rourke, E.,1,2 Whelan, P.1,2 and Emmerson, M.3
1.Environmental Research Institute, University College Cork, Cork, Ireland.
2. School of Biological, Earth and Environmental Sciences, University College Cork,
Cork, Ireland.
3. School of Biological Sciences, Queens University Belfast, Northern Ireland.
SIMBIOSYS Final Conference
Trinity College Dublin
28th June 2012
erinorourke@umail.ucc.ie

2. The impacts of bioenergy crop production on carabid and biocontrol services
• Field research • Experimental research
 Examining the impact of annual &  Examining the role of carabids
perennial bioenergy crop production in the provision of biocontrol
on carabid diversity. services.

3. Predator biomass drives natural biological control
O’Rourke, E.1, Kirwan, L.2, Cook, S.3, Murray, D.A.4,
Whelan, P.M.1 & Emmerson, M.5
1. Environmental Research Institute, University College Cork, Cork, Ireland & School of Biological,
Earth and Environmental Sciences, University College Cork, Cork, Ireland.
2. Department of Computing, Mathematics & Physics, Waterford Institute of Technology, Ireland.
3. Department of AgroEcology Department, Rothamsted Research, England.
4. VSN International LTD, 5 The Waterhouse, Waterhouse St, Hemel Hempstead HP1 1ES, England.
5. School of Biological Sciences, Queens University Belfast, Northern Ireland.

4. Justification for research
• Community functioning dependent on:
1. Identity effects
2. Diversity effects
3. Biomass effects
• Challenge to identify aspects of predator diversity most beneficial to
prey suppression.
• Need to understand the mechanisms of ecosystem functioning to allow
for informed management.

5. Hypotheses
1. Predator diversity reduces pest survival rate more than
predator biomass.
2. Interactions amongst predators lead to complementary
use of prey resources.
3. Predator identity effects and diversity effects remain
consistent as predator biomass changes.

6. Meligethes aeneus (pollen beetle) – carabid –
winter oilseed rape complex
Carabid predator biocontrol
potential exists when 2nd instar
larvae drop to the ground surface.

7. Understanding the study system
1. What is the impact of high and low pesticide management of
winter oilseed rape on:
a) crop yield
b) carabid species richness
c) carabid abundance (Field study)
2. What carabid species are most abundant at the time of pollen
beetle larval drop to the soil surface? (Field study)
3. Of the most abundant carabid species, which have the capacity to
prey on the pest? (Laboratory feeding experiment)

8. Impact of high and low pesticide management of winter oilseed
6 12 100
90
5 10
80
Carabid species richness
Crop Yield (tons per ha)
70
Carabid abundance
4 8
60
3 6 50
40
2 4
30
1 2 20
10
0 0 0
High Low High Low High Low
• 58.68% reduction in carabid abundance in crops under high
pesticide management.

9. Species Mean (±se) Mean number of
abundance larvae
killed (±se) in 2 hours
Bembidion lampros 221.33 ± 25.11 0 (*)
Generalist
Insectivore
Poecilus cupreus 161.17 ± 27.04 9.14 ± 1.14
Generalist
Insectivore
Harpalus affinis 131.17 ± 34.23 4.14 ± 0.77
Granivore
Pterostichus melanarius 34.33 ± 9.46 18.14 ± 1.61
Generalist
Carnivore

10. Simplex Monoculture - 0, 1, 0
Sp 2 Sp 2
Monoculture
100% of one species
Binary mixture - 0.50, 0.50, 0
Binary mixture
equal proportions
of two species
Centroid - 0.33, 0.33, 0.33
Centroid
even proportions
of three species
Sp 1 BIOMASS 1 (Lower) Sp 3 Sp 1 BIOMASS 2 (Higher) Sp 3
• 14 diversity treatments, at 2 carabid biomass levels.
• 2 temporal time blocks incorporated.
• Within each time block - 2 controls containing no carabids to account for natural
mortality of larvae.

11. The experimental layout
Low biomass - Monoculture High biomass - Monoculture
P. cupreus = 0.098g X 6 H. affinis = 0.051g X 24
= 0.588g = 1.224g
Response: proportion of larvae surviving
Low biomass - Binary High biomass - Binary
1 P. melanarius + 3 P. cupreus = 2 P. melanarius + 12 H. affinis =
0.195g + 0.294g = 0.489g 0.39g + 0.612g = 1.002g

12. Simplex predator-pest results
• Increased predator diversity and biomass had a
positive effect on biocontrol expressed as a
reduction of pest survival.
• Biomass effect shown to play a greater role than
the diversity effect in the delivery of service.

13. Simplex predator-pest results
• All carabid monocultures caused a decline in pest survival rates.
• Delivery of biocontrol services was greatest with respect to
monocultures of P. cupreus.
(A) Low Biomass (B) High Biomass
0.6 0.6
Survival rate 0.4 Survival rate 0.4
0.00 1.00 0.00 1.00
0.2
1.00 H. affinis 0.2
1.00 H. affinis
P. melanarius P. melanarius
0.00 0.00
0.00 0.00
1.00 1.00
P. cupreus P. cupreus

14. Simplex predator-pest results
• Pest survival declined when P. melanarius and H. affinis
and P. cupreus and H. affinis were combined in mixture
- predatory facilitation.
• Pest survival rate increased when P. melanarius and P. cupreus
were combined in mixture - behavioural interference.
(A) Low Biomass (B) High Biomass
0.6 0.6
Survival rate 0.4 Survival rate 0.4
0.00 1.00 0.00 1.00
0.2
1.00 H. affinis 0.2
1.00 H. affinis
P. melanarius P. melanarius
0.00 0.00
0.00 0.00
1.00 1.00
P. cupreus P. cupreus

15. Simplex predator-pest results
• Pest survival rate was further reduced at higher biomass.
• Identity and diversity effects are shown to remain constant,
irrespective of the level of predator biomass.
(A) Low Biomass (B) High Biomass
0.6 0.6
Survival rate 0.4 Survival rate 0.4
0.00 1.00 0.00 1.00
0.2
1.00 H. affinis 0.2
1.00 H. affinis
P. melanarius P. melanarius
0.00 0.00
0.00 0.00
1.00 1.00
P. cupreus P. cupreus

16. Conclusion
• Carabid community biomass drives the reduction in pest
survival.
• A lower level of pesticide management will:
1. Enhance carabid predator biomass.
2. Improve the delivery of carabid biocontrol services.
3. Not cause producer to suffer low crop yields.

17. Thanks
Prof Mark Emmerson & Dr Pádraig Whelan
Dr Sam Cook, Dr Darren Murray & Dr Laura Kirwan
Nigel Watts & Steve Freeman
All the farmers/landowners
Dr Roy Anderson (carabid pictures)

18. Thank you for
listening.

19. Predator-pest interaction experimental design
• Simplex design (Cornell 2002, Ramseier et al., 2005,
Sheehan et al., 2006, Kirwan et al., 2007, 2009)
• Allows the use monocultures and community mixtures
of carabids at fixed levels of overall carabid biomass
(low & high)