THE PEST AND DISEASE CONTROL
FUNCTION OF AGROBIODIVERSITY
AT THE FIELD SCALE
A. Ratnadass, J. Avelino, P. Fernandes
R. Habib & P. Letourmy
Background: Challenges facing
tropical agriculture
•
food insecurity and low-income in low-input
traditional agrosystems
•
pesticide-induced adverse impacts on human
health and the environment in intensive
systems
•
export restrictions due to strict regulations
imposed by importing countries
Agrochemistry
Human & environmental health
Soil fertility
Quantity of farm
production
Pest & disease impact
Chemical pesticide
& fertilizer
application
Beneficial organisms
Agroecology
/ Ecological
intensification
Plant species
diversification
(PSD)
Quality of farm
production
Soil biological activity
Positive impact
Negative impact
Mixed impact
Plant species diversification as the main pillar
of ecological intensification
Agroecological pathways of pest & disease regulation via
vegetational diversification in agroecosystems
Vegetational
diversification
Resource dilution
Enhancement of diversity
& activity of soil biota
Reduced impact
of pests & diseases
Physiological resistance
Soil suppressiveness
Natural enemy conservation
Barrier effects
Cycle rupture (temporal/spatial)
Pest repellency
Allelopathy
µclimate change
Pest attractiveness
1
2
3
4
5
6
7
Tropical example : the « push-pull »
system in Eastern & Southern Africa
after J. v/d Berg
Napier grass
Vetiver grass
Desmodium
•
Influence of soil organic matter
quantity and quality on the status
of Scarab beetles associated with
upland rice in Madagascar
•
Study of the various host plants of
sorghum panicle-feeding bugs in
Mali and Niger
•
Evaluation of trap crops for
management of Tomato fruit
worm on Okra in Niger
Examples of application of these principles
at Cirad at the soil and field levels
Influence of soil organic matter quantity and
quality on the status of Scarab beetles
associated with upland rice in Madagascar
•
In Madagascar, growing demand for rice and
resulting increased pressure on inundated lands has
favoured the cultivation of upland rice on hill slopes,
particularly in the high & medium altitude regions of
the island
•
If conventional tillage is used, this type of agriculture
cannot meet the objectives of both sustainability
and of high yields, due to high erosion, and to
attacks by white grubs & black beetles, particularly
in the medium-elevation region of Lake Alaotra
•
Direct seeding, mulch-based cropping (DMC)
systems have opened new prospects for upland rice,
reducing erosion, and after a few years, attacks by
white grubs & black beetles in the Central Highlands
of Vakinankaratra
Rice yield (cv FOFIFA 161) in 2002-03 (t/ha)
(/annual rice//soybean rotations, conducted since 1998 under DMC on
crop residues and under conventional tillage)
1,7
2,3
2,4
3,7
Ibity
1,7
2,8
2,6
3,2
Andranomanelatra
Conventional tillage
without
seed-dressing
Conventional tillage
with Imidacloprid
seed-dressing
DMC without
seed-dressing
DMC with
Imidacloprid
seed-dressing
Example of reduction of black beetle impact on upland
rice production in Central Highlands of
RANDRIAMANANTSOA, R., ABERLENC, H.P., RALISOA, O.B., RATNADASS, A.
& VERCAMBRE, B. 2010. Les larves des Scarabaeoidea (Insecta,
Coleoptera) en riziculture pluviale des régions de haute et moyenne
altitudes du Centre de Madagascar. Zoosystema 32:19-72.
Ab
0,0%
Ac
0,0%
Abc
0,0%
Bricoptis variolosa
Ab
0,0%
Ac
0,0%
Ac
0,0%
Hexodon unicolor unicolor
Ab
8,3%
Ac
25,0%
Aab
50,0%
Heteronychus plebejus
Ab
12,5%
Aabc
37,5%
Aabc
37,5%
Heteroconus paradoxus
Ab
25,0%
Aab
75,0%
Aa
66,7%
Heteronychus bituberculatus
Bb
37,5%
Aa
100,0%
Aa
91,7%
Heteronychus arator rugifrons
Aa
100,0%
Aa
87,5%
Aa
83,3%
Apicencya waterlotii
Plain soil+rice straw
Plain soil +cow dung
Plain soil
Damage to rice roots (%)
Scarab beetle species
Objective: Minimizing Scarab
beetle role as pests and optimizing
their function as ecosystem
engineers in multiple
species-based Direct-seeding, Mulch-species-based
Cropping (DMC) systems
so
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Heteronychus arator rugifrons
Apicencya waterloti
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10%
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Heteronychus bituberculatus
Heteronychus arator rugifrons
Apicencya waterloti
0%
10%
20%
30%
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50%
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80%
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100%
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Heteroconus paradoxus
Heteronychus bituberculatus
Heteronychus arator rugifrons
Apicencya waterloti
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
%
c
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Heteronychus plebejus
Heteroconus paradoxus
Heteronychus bituberculatus
Heteronychus arator rugifrons
Apicencya waterloti
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
%
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Hexodon unicolor
Heteronychus plebejus
Heteroconus paradoxus
Heteronychus bituberculatus
Heteronychus arator rugifrons
Apicencya waterloti
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
%
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Sorghum panicle-feeding bugs in West
and Central Africa
Management of plant bugs on castor bean
to reduce sorghum infestation
•
Studies conducted at the village level in
1998-99 in resp. 5 and 16 villages of the
Kolokani region, Mali
•
Split-plot designs with 3 factors: sorghum
cv (8); date of sowing (2); and « castor
treatment » (2-3):
–
1998 : sorghum fields located in the vicinity vs
remote from castor plants
–
1999 : all sorghum fields located in the vicinity
of castor, with management of castor spikes
(insecticide spraying or spike manual removal)
vs no treatment)
ICSH 890 02 Gad iaba ni 87 W 810 ICSV 107 9 ICSV 106 3 94-E PR S-G II-1 122 Mal isor 8 4-7 Bib awili Far DOS1 Far DOS2 Close DOS2 Close DOS1 0 100 200 300 400 500 600 N o . h e a d -b u g s p e r 5 p a n ic le s C u l ti vars
1998
ICS H 8 9002 ICS V 1 063 ICS V 1 079 Gad iaba ni Mal isor 8 4-7 87 W 810 Bib awili 94-E PRS -GII -112 2 Removed DOS1 Removed DOS2Insec tic ide DS1 Insec tic ide DS2
Control DOS1 Control DOS2 0 200 400 600 800 1000 1200 1400 1600 1800 N o . h e a d -b u g s p e r 5 p a n ic le s Cultivars
1999
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Spider plant
Jujube
Castor Bean
Pigeon pea
Sesbania
Mango
Cotton
Rattle-box
Sorghum
Alternate hosts and life-cycle of Eurystylus oldi
in Sudano-Sahelian West Africa
In Niger, in terms of trap cropping & conservation biological
control potential for Helicoverpa armigera on okra:
–
Pigeon Pea > Sorghum > Cotton
0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 05/09/2008 12/09/2008 19/09/2008 26/09/2008 03/10/2008 Dates d'échantillonnage N o . d 'H e li c o v e rp a /p la n t d e g o m b o ( e ff e c ti fs c u m u lé s ) Témoin Traité insecticide Bordure sorgho Bordure pois d'angole a a ab b 0% 2% 4% 6% 8% 10% 12% 14% 16% 18% 20%
Témoin Traité insecticide Bordure sorgho Bordure pois d'angole
Traitements % F ru it s a tt a q u é s a b ab ab
-+
+/-Effects against other pests
+
-Potential for “assisted” control
-+
-Conservation biological control effectiveness
-+
Ease of visual inspection and manual control
+
-+
Attractiveness period duration
+/-+
Attractiveness level
Cotton
Sorghum
Pigeon Pea
Plant species
Criteria
Pros and cons of three plant species tested in Niger as perimeter trap plants
around okra fields for Tomato Fruit Worm (Helicoverpa armigera) control
Importance taking into account
upper scales
•
Emerging adults of « plastic » white grubs species will
damage neighbouring upland rice fields that are not
managed in an agroecological manner
•
In the case of trap-cropping (e.g. vs TFW on okra), or
cycle-breaking strategies (e.g. panicle-feeding bugs on sorghum),
if the alternate host used has no dead-end properties, care
should be taken not to turn a « sink » for pests into a
« source » of infestation at upper spatial and temporal
scales
•
At an even larger scale, dead-end trap plants that are both
highly attractive for egg-laying by adult female pests and
unfit for the development of their progeny, may also end
up selecting pest populations that will overcome this
THE CIRAD OMEGA3 PROJECT’S APPROACH AND CASE STUDIES
O
ptimisation des
M
écanismes
É
cologiques de
G
estion
des bio-
A
gresseurs pour
une
A
mélioration
durable de la
productivité des
A
grosystèmes”
Low
(Generalists)
B
io
-A
g
g
re
s
o
r
d
is
p
e
rs
a
l
a
b
il
it
y
High
(Specialists)
Low
High
Bio-Aggressor specificity
Landscape
Fie
ld
Soil
PSD deployment scale
White grubs
& Striga
/Upland rice
Black pod rot
/Cocoa
Mirid bugs
/Cocoa
Leaf rust
/Coffee
Berry
borer
/Coffee
Fruit flies
/Cucurbit
vegetables
Fruit worm
/Tomato
& Okra
White fly
/Tomato &
Okra
Bacterial wilt
/Tomato
Bacterial wilt
/Tomato
Fruit worm
/Tomato
& Okra
White fly
/Tomato &
Okra
Fruit flies
/Cucurbit
vegetables
Fruit worm
/Tomato
& Okra
White fly
/Tomato &
Okra
Black pod rot
/Cocoa
Mirid bugs
Ω
3
’s methodological flow-chart
Hypotheses regarding PSD
effects on pests & diseases
generated by observation
Experimental checking of
suspected PSD effects
Ideotypes of PSD-based
cropping systems resilient
to pests & diseases
Validation of models
through observation
and experiments
Adding to the
knowledge base
Parameterization
of existing models
Indicators
Scenarios &
decision-making rules
Construction of
mechanistic models
Thanks to our partners:
•
ICRISAT (Niger & Mali)
•
ICRISAT, INRAN, University of Niamey (Niger)
•
FOFIFA, University of Antananarivo & TAFA
(Madagascar)
Session 3: The functional role of agrobiodiversity: from farms to landscapes
THE PEST AND DISEASE CONTROL FUNCTION OF AGROBIODIVERSITY AT THE FIELD SCALE
A. Ratnadass1, J. Avelino2, P. Fernandes3, R. Habib4 & P. Letourmy5
1. Cirad - HortSys research unit – Icrisat – BP 12404 – Niamey - Niger - Email: ratnadass@cirad.fr
2. Cirad - Controlling Pests and Diseases in Tree Crops research unit – IICA/PROMECAFE – San José – Costa Rica
3. Cirad - HortSys research unit – Pram – Le Lamentin - Martinique 4. Cirad – Persyst Scientific Department Director – Montpellier – France 5. Cirad – Annual Cropping systems research unit – Montpellier – France
Abstract - Among agrobiodiversity enhancement options, the planned introduction and
management of plant species diversity (PSD) in agroecosystems is a promising way of breaking with “agrochemistry” and moving to “agroecology”. Besides agronomic and economic benefits, PSD may reduce pest and disease impact via several causal pathways. We report on instances pest and disease regulation processes in tropical cropping systems, emphasizing the soil and field levels. We thus studied the influence of soil organic matter quantity and quality on the status of Scarab beetles associated with upland rice in Madagascar, in view of minimizing their role as pests and optimizing their function as ecosystem engineers in multiple species-based Direct-seeding, Mulch-based Cropping (DMC) systems. We also studied in West Africa the various host plants of sorghum panicle-feeding bugs, in order to manage these pests (and grain molds they transmit) via a combination of trap cropping and cycle rupture, and the potential of several trap crops for managing the tomato fruitworm (and in a subsidiary way the cotton white fly and the TYLC-transmitted disease) on okra. Although processes studied primarily operate at the field level, results obtained stress the need to take into account larger scales, both spatial and temporal. This approach is developed in the Cirad Omega3 project which builds on tropical case studies, representing a broad range of PSD scales and deployment modalities (soil, field, landscape, and DMC, horticultural and agroforestry systems), according to a typology of pests and pathogens based on life-history traits the most amenable to manipulation by PSD (specificity and dispersal ability). Further to results aiming at immediate impact, more generic results are expected, after formalizing the ecological processes studied, namely decision-making rules which will help set up models to predict the impact of PSD on pests and pathogens with similar life-history traits.
