Transcript 2001 Seed Dealer Update Meetings

Impact of Cultural Practices
on Soybean Aphid Incidence,
Soybean Yield, and Virus
Incidence
John Gaska, Dr. Craig Grau, Nancy
Kurtzweil, and Dr. Dave Hogg
Depts. of Agronomy, Plant Pathology and Entomology
UW Madison
UW MADISON AGRONOMY
Possible Cultural Practices
for Aphid-Virus Control
•
•
•
•
•
•
•
•
•
Date of Planting
Seeding rate
Row width comparisons
Varietal selection
Tillage practices
Fertility and fertilization
Rotations?
Canopy Density
Virus free seed
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J. Gaska UW Madison 2002
Cultural Practices for Soybean Aphid Control
Observations in 2000
• High soybean aphid pressure in late planted
fields
• High soybean aphid pressure in low plant
population areas
• First instinct is to use insecticides
• Cultural practices may help also
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J. Gaska UW Madison 2002
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J. Gaska UW Madison 2002
Effect of planting date and variety on aphid incidence.
Aphid Count 8/11
Arlington, WI. 2000
140
120
100
80
60
40
20
0
LSD 0.10
PD=24
Var=25
PDxV=ns
4-May
MADISON
Grau, UW
Kurtzweil,
2000 AGRONOMY
5
AG2401
Span 201
Span 250
22-May
1-Jun
Date of Planting
J. Gaska UW Madison 2002
Effect of planting date and variety on virus symptoms.
0-11 Horsfall-Barratt
Arlington, WI. 2000
5
4
LSD 0.10
PD=0.7
Var=0.5
PDxV=ns
AG2401
Span 250
3
2
1
0
4-May
MADISON
Grau, UW
Kurtzweil,
2000 AGRONOMY
6
Span 201
22-May
Date of Planting
1-Jun
J. Gaska UW Madison 2002
Materials and Methods
2001 Date of Planting Study
• Location:
Arlington Ag Research Station
• Expt. Design:
RCB
• Reps:
4
• Variety:
DSR-215RR
• Row width:
30”, 120,000 seeds/acre
• Planting dates: May 9, May 29, June 7
• No insecticides were used
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J. Gaska UW Madison 2002
Soybean Aphid Date of Planting
Yield (bu/a)
Arlington, WI 2001
64
62
60
58
56
54
52
50
48
46
62.8
55.3
52.8
9-May
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29-May
Planting Date
7-Jun
J. Gaska UW Madison 2002
Soybean Aphid Population vs. Planting Date
400
350
300
250
200
150
100
50
0
R3 stage
R3 stage
7-June
27-May
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Sampling Date
Au
g
24
-
Au
g
17
-
Au
g
10
-
ug
3A
Ju
l
27
-
Ju
l
9-May
20
-
13
-
Ju
l
Aphids/Youngest Trifloliate
Arlington, WI 2001
J. Gaska UW Madison 2002
Soybean Aphid On-Farm Observations
Planting Date Variations
Various WI Locations - 2001
Yield Difference (bu/a)
20
+8.7
+4.7
+7.7
15
10
5
0
<May15
-5
May 16-May31
June 1-June 28
Planting Date
10
UW Jensen
MADISON
AGRONOMY
2001-Wedberg,
UW Dept.
of Entomology
J. Gaska UW Madison 2002
Which one does an aphid prefer?
Materials and Methods
2001 Row Spacing x Seeding Rate Study
• Location:
Arlington Ag Research Station
• Expt. Design:
RCB-Split Plot
• Reps:
4
• Variety:
DSR-215RR
• Row width:
7.5” and 30”
• Population:7.5” 150K, 200K, and 250 K seeds/acre
30” 75K, 125K and 175K seeds/acre
• Planting date:
May 9
• No insecticides were used
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J. Gaska UW Madison 2002
Soybean grain yield at two row widths
and three seeding rates.
Arlington, WI. 2001
Yield (bu/a)
75
70
LSD 0.10
RS=6.3
SR=3.4
RSxSR=7.4
Low
Medium
High
65
60
55
50
45
7.5"
Row Spacing
30"
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Soybean aphids at two row widths and three seeding rates
on July 19 and July 26. Arlington, WI. 2001.
July 19
160
Aphids / youngest trifoliate
Low
Medium
July 26
160
Low
High
140
140
120
120
100
100
80
80
60
60
40
40
20
20
0
0
7.5" Row Spacing 30"
Medium
High
7.5" Row Spacing 30"
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Summary
• Planting date
significantly affected
aphid numbers
• No conclusions on viral
activity due to planting
date or plant density
• Insecticides may have
to be used if aphid
populations reach
damaging levels
• Future research will
build on aphid
colonization numbers
and correlate GDU’s
with aphid numbers
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Conclusions and Recommendations
for Cultural Management of
Soybean Insect-Virus Complex
Early Planting Date
Late Planting Date
• Advantage
– Maintain dense canopy
– High yield potential
– Lower aphid density
– Lower virus incidence
• Disadvantage
– Bean leaf beetle
– BPMV
• Use higher seeding rate
for denser canopy
• May require an insecticide
application
• Very late plantings may be
able to mix herbicide and
insecticide
Use of virus free seed
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J. Gaska UW Madison 2002
Thank You!
• Questions?
• Comments?
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The Soybean Virus-Insect Team
• Entomology
– John Wedberg
– Dave Hogg
– Tom German
– Tom Klubertanz
– Robb Alleman
– Bob Ellingson
– Scott Myers
• Plant Pathology
– Nancy Kurtzweil
– Mary Lee
– Ana Mondjana
– Lee Nolden
• Agronomy
– Chris Boerboom
– John Gaska
– Palle Pederson
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