Effect of strip cropping of wheat, corn and
soybean on natural control of soybean
aphid and other insect pest species
Geneviève Labrie
Bernard Estevez
Éric Lucas
Introduction
• In organic crop: prevention of insect pest outbreaks
One way = to increase diversity and heterogeneity
on the farm
Effect of ↑ diversity on insect pest species:
• Pest species more attracted by concentrated resource
• Localisation of the plant is reduced when diversity ↑
Effect of ↑ diversity on natural enemies:
• Presence of alternative resources (pollen, nectar, prey)
• More habitats to reproduce, laying eggs…
Strip cropping
• Strips of 4 to 6 rows of two to four crops are used to
-
reduce insect pest incidence;
-
reduce disease transfer and
-
deliver environmental benefits such as greater soil
and water conservation potential
• Strips of wheat and alfalfa (1m width) (Ma et al. 2007)
→ more spider mite predator
→ more parasitized cereal aphid
• Strips of corn and soybean (2 rows; 9 rows) (Wang and Ba 1998)
→ less soybean aphid in strips (↓
↓ olfactive cues)
→ 3x more natural enemies
Objectives
Measure the effect of strip cropping of soybean, corn
and wheat on
1- Major pest species of these crops
2- Abundance of natural enemies
3- Crop yield
Soybean
aphid
Material and Methods
One farm:
36m width
- Les Cèdres (near Valleyfield)
- 187 hectares used
- Organic management
- Wheat, soybean, corn and
vetch (manure year before corn)
- Rotation each year
18m width
Two strip width:
- optimize machinery
- reduce soil compaction
…material and methods
Treatments:
Strips of 18 m x 1 km long
Strips of 36 m x 1 km long
Single-crop of 180 m x 1
km
2 replicates by crops and
treatments (= 18 crops sampled)
Insect sampling:
1x by week
Wheat: sweep net (June-August)
Soybean and Corn: visual
observation (June to September
or October)
18 stations by field
18 m Corn
18 m Soybean 18 m Wheat
Results
In soybean:
2007: 380 000 soybean aphids
2008: 6500 soybean aphids Soybean aphid
In corn:
2007: 15 000 insect pest
2008: 2000 insect pest
Aphids (4 sp)
European corn borer
Corn rootworm
In wheat:
2007: 42 000 insect pest
2008: 14 000 insect pest
Aphids (4 sp) Collembola
Thrips
…results in soybean
160
140
b
120
c
100
18m
80
b
60
36m
single-crop
a
40
20
b
b
a
a
*
*
Ju 1 9
ne
28
Ju
ly
Ju 3
ly
1
Ju 0
ly
1
Ju 7
ly
2
Ju 2
ly
A u 31
gu
A u st
gu 7
s
Au t 1
gu 5
s
Au t 2
2
Se gus
pt t 2
Se em 9
pt be
em r 9
be
r1
5
a
ne
Ju
ne
14
.
0
Ju
Number of winged aphids/plant (± SE)
Winged soybean aphids in 2007
Weeks
More winged soybean aphids in single-crop than in strips:
attraction to concentrated resource?
Soybean aphid in 2007
2500
2000
c
b
c
b
1500
1000
500
b
a
a
a
a
a
a
*
31
Au
gu
st
Au
7
gu
st
15
Au
gu
st
22
A
ug
us
Se
t2
pt
em 9
S
be
ep
r9
te
m
be
r1
5
*
Ju
ly
22
Ju
ly
17
a
Ju
ly
10
Ju
ly
Ju
ly
28
Ju
ne
19
Ju
ne
Ju
ne
3
*
0
18m
36m
single-crop
R6
ab
b
b
14
.
Number of soybean aphids/plant (±SE)
…results in soybean
Weeks
100% sampled plants infested by soybean aphid on June 28th
Economic injury level reached before stage R6
…results in soybean
25
20
18m
36m
single-crop
c
15
b
b
10
b
a
5
a
b
a
b
a
b
a
a
a
a
Ju
14
.
ne
1
Ju 9
ne
28
Ju
ly
3
Ju
ly
10
Ju
ly
17
Ju
ly
22
Ju
ly
Au 31
gu
A u st 7
gu
st
15
Au
gu
s
A u t 22
g
Se ust
29
pt
e
Se mb
e
pt
em r 9
be
r1
5
0
ab
a
b
Ju
ne
Number of natural enemies by plant (±
SE)
Natural enemies of soybean aphid in 2007
Weeks
More natural enemies in 18m and 36m strips during
aphids peak infestation
a
Weeks
ab
b
a
a
a
a
9
m
b
e
pt
em r 9
be
r1
5
a
Se
a
t2
b
pt
e
15
2
a
Se
*
t2
a
gu
s
ab
Au
a
5
a
b
t1
c
gu
s
c
Au
1500
t7
10
31
Au
gu
st
Au
7
gu
st
15
Au
gu
st
22
Au
gu
st
Se
29
pt
e
Se mb
e
pt
em r 9
be
r1
5
2000
gu
s
20
31
a
gu
s
b
22
b
Au
5
Ju
ly
17
10
500
22
Ju
ly
Ju
ly
1000
Ju
ly
0
17
10
3
*
Ju
ly
Ju
ly
Ju
ly
Ju
ly
14
.
Ju
ne
1
Ju 9
ne
28
0
Ju
ly
3
28
19
.
Ju
ne
Number of soybean aphids/plant (±SE)
2500
Au
ne
Ju
ly
Ju
14
ne
e
25
Ju
Ju
n
Number of natural enemies by plant (±
SE)
…results in soybean
Dynamics in soybean
b
b
18m
36m
single-crop
b
a
a
*
Weeks
c
b
18m
36m
single-crop
b
b
a
b
a
Natural enemies
synchronized with
soybean aphids
in 18 and 36m
strips
Natural enemies
not synchronized
in single-crop
…results in soybean
18m
36m
single-crop
50
45
40
35
30
25
20
15
10
5
0
a
a
b
ab
b
r8
m
be
8
Se
pt
e
gu
st
2
Au
gu
st
1
9
2
Au
gu
st
1
Au
gu
st
5
Au
gu
st
1
25
Au
Ju
ly
15
Ju
ly
Ju
ly
4
Ju
ly
.
27
8
b
ne
Ju
Number of soybean aphid by plant (±SE)
Soybean aphid in 2008
Weeks
2x less soybean aphids in strips than in single-crop
…results in soybean
18m
36m
single-crop
2,5
2
1,5
a
1
0,5
r8
8
m
be
pt
e
Se
gu
s
Au
Au
gu
s
t1
t2
9
2
t1
gu
s
Au
gu
st
5
a
Au
gu
st
1
Au
25
Ju
ly
15
Ju
ly
8
Ju
ly
Ju
ly
27
ne
4
0
Ju
ab
a
ab
b
.
Number of natural enemies by plant (±SE)
Natural enemies of soybean aphid in 2007
Weeks
More natural enemies in 18m strips at soybean stage R3
…results
Effects of strip cropping in soybean
• Huge infestation of soybean aphid in 2007
• 2x less soybean aphids in strips than in single-crop for
both years of study
• Attraction of winged soybean aphid by single-crop?
• More natural enemies during infestation
• Presence of natural enemies could help to delay soybean
aphid population increase
→ Promising management practice in soybean
Se
be
t5
t1
25
15
8
r1
7
r8
t2
8
t1
9
t1
2
be
gu
s
gu
s
pt
em
Au
Au
gu
s
gu
s
ly
gu
s
pt
em
Se
Weeks
Au
Au
Au
Ju
ly
ly
4
4,5
Ju
ly
.
11
27
Ju
ne
ne
5
Ju
Ju
Ju
Mean number of natural enemies (±SE)
…results
Dynamics of natural enemies in strips in 2008
18 m strips
wheat
flowering
4
3,5
3
2,5
2
1,5
1
0,5
0
…results
Dynamics of natural enemies in strips in 2008
wheat
soybean
corn
5
4,5
flowering
4
3,5
3
2,5
2
1,5
1
0,5
t5
Au
gu
st
12
Au
gu
st
19
Au
gu
st
Se
28
pt
em
be
Se
r8
pt
em
be
r1
7
t1
Au
gu
s
Au
gu
s
25
ly
Ju
Ju
ly
15
8
ly
Ju
Ju
ly
.
27
Ju
ne
Ju
ne
4
0
11
Mean number of natural enemies (±SE)
18 m strips
Weeks
Movement of natural enemies from strips of wheat to
other strips
Dynamics of natural enemies in single-crop in 2008
Single-crop
wheat
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
corn
Ju
n
e
Ju 11
ne
27
.
Ju
ly
4
Ju
ly
Ju 8
ly
15
Ju
ly
A u 25
gu
s
Au t 1
gu
Au st 5
gu
s
A u t 12
gu
s
A u t 19
g
Se ust
pt
28
S e em
pt ber
em
8
be
r1
7
Mean number of natural
enemies (±SE)
soybean
Weeks
No movement of natural enemies between single-crop of
wheat,corn and soybean
Other results
Other interesting results:
- 30 to 50% parasitism of aphids in strips
of wheat in 2007
- More ladybeetles in strips of corn
than in single-crop both years
Crop yield similar between strips and single-crop: strips
implanted only 3 years ago
Conclusion
Strip cropping :
- reduce population of soybean aphids (2x)
- attract and retain more natural enemies = enhancement of
biological control
Natural enemies:
- more natural enemies in soybean, corn
H. axyridis
and wheat for both years
Aphid midge
- synchronism with pests in strips
- possibility of movement of natural enemies between strips
Two years of study very different: more data needed
Strip cropping is a promising tool to enhance natural control
of insect pest species in organic management
Acknowledgements
La Ferme Longprès
Technicians: Louise Voynaud, Noémie Charest-Bourdon
Jacinthe Tremblay, Florent Renault
Club BioAction
Laboratoire de lutte biologique de l’UQAM