3rd Africa Rice Congress Theme 2: Intensification and diversification Mini symposium: Rice pests: evidence of effects and management Author: Andrianaivo

1. INTEGRATED AND LOCALLY ADAPTED
STRIGA ASIATICA CONTROL:
Combining a Zero-tillage Rice–Maize
Cover-Crop Rotation System with
Resistant Rice Varieties
Alain Paul Andrianaivo
(SRiD-FoFiFa, Antananarivo, Madagascar)
Roger Michellon
(SCRiD-Cirad, Antsirabe, Madagascar)
Jonne Rodenburg
(AfricaRice , Dar es Salaam, Tanzania)
Meva Tahiry Randrianjafizanaka
(Univ. Tulear ,Madagascar)

2. Striga asiatica (L.) Kuntze
• Common weed in the midwest of the Vakinankaratra
region (800-1000 a.s.l.)
• Cropping systems:
Rice//maize
• Serious yield losses

3. Objective
• Soil conservation
management
•
Integrated
Striga
control

4. Hypotheses
• Combining zero-tillage with intercropping will
- protecting the soil
- improving the organic matter content
- reduce Striga infestation rates
• Stylosanthes has a suppressive effect on
Striga
• Striga resistant rice varieties should enhance
Striga suppression

5. Material and methods
• Site Selection: Ivory
• Treatments and experimental set-up
 three seasons (2011-2014)
 Split-Split plot design (6 rep.)
 4 cropping systems(S1-S4)
 3 rice varieties (V1-V3)
 1 maize locally variety

6. Material and methods
• S1: Rice//Maize + tillage + Crop residue removal
• S2. Rice // Maize + Cowpea + Mucuna
• S 3. Rice // Maize + Vigna umbellata
• S4. Rice + Stylosanthes // Maize+ Stylo.
 V1: B 22. , Striga susceptible
 V2: Nerica 9. Striga moderately resistant
 V3: Nerica 4. Striga resistant

7. Material and methods
Phase
Season 1 (2011-2012)
Season 3 (2013-2014)
Season 2 (2012-2013)
Rice
Maize
P2
Maize
Rice
P1
Rice
Maize + cowpea + mucuna
P2
Maize + cowpea + mucuna
Rice
P1
Rice
Maize + Vigna umbellata
P2
Maize + V. umbellata
Rice
P1
Rice + Stylosanthes
(year 1)
Maize + Stylosanthes (year 2)
P2
Maize + Stylosanthes (year 1) +
supplementary Stylosanthes residues
Rice in Stylosanthes residues of year 11
System 4
System 1
P1
System 2
Tillage and
residue
management
System 3
System
Table 1. Cropping systems plan for season 1 to season 3.
Tillage,
No residues
Zero-tillage +
Residues

8. Results
Table 2. Striga numbers (10 m-2) in rice at harvest
Rice variety
Season
System
Mean
B22
NERICA-9
NERICA-4
S1: Rice//Maize
38.9
2.1
0.2
4.3
S2: Rice//Maize cowpea + mucuna
6.9
1.7
1.3
2.7
2011/2012
S3: Rice//Maize V. umbellata
6.3
2.5
0.6
2.4
1
S4: Rice + Stylosanthes//maize + Stylosanthes
9.1
1.6
0.9
2.7
Mean 11.3
A2
2.0
B
0.7
B
S1: Rice//Maize
159.4 a4
37.4
ab
0.3
cd
65.7 x5
S2: Rice//Maize cowpea + mucuna
38.8
ab
22.4
ab
2.6
cd
21.3 x
2012/2013
S3: Rice//Maize V. umbellata
14.9
bc
17.5
ab
0.4
cd
11.0 x
3
S4: Rice + Stylosanthes//maize + Stylosanthes
3.9
bcd
1.9
cd
0.00
d
1.9
A
19.8
B
0.8
C
25.0
Mean 54.3
1
In the 2011-2012 cropping season, phase 1, S1 till S3 are all rice-only.
2
Values in the same row followed by different letters (A-C) are significantly different (P<0.05).
3
Results on rice in season 2012-2013 are derived from plots that were preceded by maize or maize and cover crops in the 2011-2012 season (earlier referred to as phase 2).
4
Values followed by different letters (a-d) are significantly different (P<0.05).
5 Values
in one column followed by different letters (x or y) are significantly different (P<0.05).
y

9. Results
Table 3. Striga numbers (10 m-2) in maize in season 2 near harvest time, following
different cropping systems and with different rice varieties in the preceding 2011/2012
season.
Rice variety in preceding season
Season
System
B22
NERICA-9
NERICA-4
Mean
S1: Rice//Maize
306.8
a1
100.2
a
19.1
ab
142.0
x2
S2: Rice//Maize cowpea + mucuna
35.5
a
38.5
a
43.8
ab
39.3
y
S3: Rice//Maize V. umbellata
90.5
a
63.3
a
19.6
a
57.8
y
S4: Rice + Stylosanthes//maize + Stylosanthes
0.0
b
0.0
b
0.0
b
0.0
z
108.2
A3
50.5
20.6
B
2012/2013
Mean
1
Values followed by different letters (a-d) are significantly different (P<0.05).
2
Values in ‘Mean’ column followed by different letters (x or y) are significantly different (P<0.05).
3
Values in the ‘Mean’ row followed by different letters (A-C) are significantly different (P<0.05).
AB

10. carry-over effect of resistance in Maize//Rice
Maize//NERICA9
Maize//B22
Maize//NERICA4

11. Results
Table 4. Rice yields (t ha-1) following different cropping systems and rice varieties
Season
System
Rice variety
B22
NERICA-9
Mean
NERICA-4
S1: Rice//Maize
S2: Rice//Maize cowpea + mucuna
2011/20121
1.8
1.9
2.1
1.9
1.9
1.7
1.7
1.73
1.8
1.8
1.9
S3: Rice//Maize V. umbellata
S4: Rice + Stylosanthes//maize + Stylosanthes
Mean
S1: Rice//Maize
1.8
c2
2.3
bc
2.2
bc
2.1
y3
S2: Rice//Maize cowpea + mucuna
2.9
ab
3.2
a
3.3
a
3.2
x
S3: Rice//Maize V. umbellata
2.5
abc
1.9
c
2.2
bc
2.2
y
S4: Rice + Stylosanthes//Maize + Stylosanthes
2012/2013
0.74
d
0.5
d
0.5
d
0.6
z
2.0
A5
2.0
A
2.1
A
Mean
1
In the 2011-2012 cropping season, phase 1, S1 till S3 are all rice-only; therefore these systems are combined in the analyses, for comparison with rice - Stylosanthes. No
significant yield differences were observed this season.
2
Values followed by different letters (a-d) are significantly different (P<0.05).
3
Values in the ‘Mean’ column, followed by different letters (x-z) are significantly different (P<0.05).
4
This system should be evaluated in the third year following all of the three stages: 1. Rice with Stylosanthes (year 1) followed by 2. Maize with Stylosanthes (year 2),
concluded by 3. Rice sown in the slashed residues of the Stylosanthes.
5
Values in the same row followed by different letters (A-C) are significantly different (P<0.05).

12. Conclusions
• Striga densities are reduced by S2, S3 and S4. Particulary
with Vigna umbellata and Stylosanthes guianensis.
• With respect to rice yields, the best system, is S2 :(Rice//Maize
+cowpea+mucuna
•
For subsistence farmers in central Madagascar, that have to
deal with soils that are both highly infested by Striga asiatica
and highly vulnerable to degradation, a system of rice rotation
with a maize – legume intercrop following zero-tillage, without
removing crop residues, is likely to represent an attractive
alternative to the current practice

13. Acknowledgements
CGIAR /GRISP
Cirad
Merci de votre aimable
attention !