white grubs, scarabaeidae larvae (insecta, coleoptera) control by plants in ca: effects on...
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Bodovololona Rabary,
Naudin K, Letourmy P, Mze Hassani I, Randriamanantsoa R, Michellon
R, Rafarasoa L, Ratnadass A
White grubs, Scarabaeidae larvae
(Insecta, Coleoptera) Control by
plants in conservation agriculture:
effects on macrofauna diversity
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• Context & Objective– Uplands rice production and constraints– White grubs diversity and impacts– Soil biofunctioning and macrofauna functional
groups– Hypothesis and Objective
• Experimental setup – The study site and layouts– Sampling methods
• Results and discussion• Conclusion
Outline
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Uplands rice production and constraints
• Rice, staple crop and food in Madagascar,
• Grown on 1.3 million Ha, 29% are upland rice
• Production of upland rice varieties is steadily
increasing in Madagascar
• Rice farmers are encountering several
constraints of which:
– High crop damage/loss caused by rice diseases
and pests, including weeds.
– Most pest damages are caused by white grubs
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Larva and adults of Madagascar’sScarabaeoidea (pests)
Heteroconusparadoxus
Heteronychusbituberculatus
Heteronychusarator rugifrons
Apicencyawaterloti
MELOLONTHIDAE
DYNASTIDAE
(Randriamanantsoa et al., 2010)
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White grubs damages
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Attack at root or crown levels according to species, death of plant
Attack might be as severe as here
The more efficient control method of white grubs is until now ‘pesticides ‘
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Larva of Madagascar’s Scarabaeoidea(Non-pests)
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Hexodon unicolorunicolor
Bricoptisvariolosa Serica sp.
Euryiomiaargentea
SERICIDAEDYNASTIDAE CETONIIDAE CETONIIDAE
(Randriamanantsoa et al., 2010)
Some of them shows "soil engineering" behaviour
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Soil biofunctioning and macrofauna
functional groups
• Promote nutrient cycling,
• Participate on soil organic matter dynamics, C sequestration, emission of greenhouse gases control
• Change the soil structure and water regime
• Encourage the growth and the health of the plants.
build the quality and health of the soil over time
Increase the quantity and the efficiency of plant nutrients uptake
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(Lavelle et al., 1997; Frouz et al. 2001; Hättenschwiler& Gasser, 2005)
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Major pathways for reducing the impact of
pests and diseases via plant species diversity
in agroecosystems (Ratnadass et al., 2011)
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Hypothesis and Objective
Hypothesis: Increase in plant biodiversity + No-tillage + cover crops macrofauna diversity positive impact on pests.
Research question: If the plants have positive impacts on pests, what are their effects on macrofauna biodiversity (Non-target species)?
Approach based on functional groups diversity
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Macrofauna’s food and nutrition
• Predators (other fauna)
• Phytophagous (plants)
• Saprophagous (decomposing organic matter)
• Detritiphagous (detritus)
• Xylophagous (wood-eating)
• Coprophagous (feces)
• Geophagous (soil)
Functional groups
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Characteristics
of the study
area
AntsirabeAndranomanelatra
Altitude: 1600 m.a.s.l.
Mean annual rainfall: 1450 mm
Central high plateau with high-
altitude tropical climate
Ferrallitic clayey soil (clay
61.90 %, pH: 5,7)
(19°46’ 45’’S, 47°06’ 25’’ E)
More than 80 inhabitants / km²
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F1 F8
F2 F7
F3 F6
F4 F5
C1 C2 C3 C4
C8 C7 C6 C5
A1 A2 A3 A4 B1 B2 B3 B4
A8 A7 A6 A5 B8 B7 B6 B5
D1 D2 D3 D4 E1 E2 E3 E4
D8 D7 D6 D5 E8 E7 E6 E5
N
Sole Rice (NT)
Rice + Beans (NT)
Rice + Beans (CT)
Rice + Vetch (NT)
Rice + Eleusine + Crotalaria (NT)
Rice + Cleome + Cosmos + Tagetes (NT)
Rice + Brachiaria (NT)
Rice + Radish (NT)
Legend
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Experimental field layout in 2009-
2010
NT = Direct seedingCT = Conventional Tillage
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hairy vetch (Vicia villosa)
Brachiariamulato Crotalaria grahamiana
Cleome hirta Tagetes minuta
Cosmos caudatus
Fodder Radish (Raphanus sativus)
Plants used as cover
crops for controlling
White grubs
Eleusine coracana
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Methods
• Modified TSBF : 1 monolith of 25 cm x 25 cm x 30 cm per plot
• Cut into litter and three layers: 0-10 cm, 10-20 cm, and 20-30 cm
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Methods (cont’d)
• Hand sorting of invertebrates > 2 mm
• Identification (taxa), counting and weighing of Macrofauna. Conservation in alcohol 70 °
• ANOVA of transformed data for non-parametric tests.
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0200400600800
10001200140016001800
Macrofauna functional group density (Individuals m-2) Non-Identified
Saprophagous
Geophagous
Predators
Detritiphagous*
Phytophagous
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Mean abundance of Macrofauna
within cropping systems
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0
20
40
60
80
100
120
140
Detritiphagous density (individuals m-2)
aa
a
b
a
ab
aa
Abundance of detritiphagous
within cropping systems
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18
0
5
10
15
20
25
Macrofauna functional group biomass(g m-2)
Non-Identified
Saprophagous
Geophagous
Predators
Detritiphagous
Phytophagous*
Mean biomass of Macrofauna within
cropping systems
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19
0123456789 Phytophagous biomass (g m-2)
b
a
a
a
a
a
ab
a
Phytophagous biomass within cropping systems
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Conclusion & Perspectives
• Radish seems promising for phytophagous control.
• In addition, it did not reduce macrofauna diversity and abundance.
• Vetch was also favourable for macrofauna abundance but it did not
express white grub pest control potential.
• Our results emphasise the importance of studying a wide range of
plants as cover crops or residue mulch for soil pest control
Perspectives
• specific pest-suppressive effects of plants
• explore more plant species.
• Study the mechanisms involved
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Thank you