Institute of Ag Professionals
Proceedings of the
2015 Crop Pest Management Shortcourse &
Minnesota Crop Production Retailers Association Trade Show
www.extension.umn.edu/Ag-Professionals Do not reproduce or redistribute without the written consent of author(s).
Soil Insecticides, Bt Traits & Corn Rootworm: Are We Coming
Full Circle?
Ken OstlieUniversity of Minnesota – Entomology
(612)750- 0993 [email protected]
What’s the Current Situation with Corn Rootworms and Bt-RW Resistance?
Roller coaster ride in resistance-related Bt-RW performance problems (peaking in 2012-2013)
Only western corn rootworm issue so farMajority of fields corn after corn with multiple-year
history of trait; no problems in rotated fields so far Cry3Bb1 (VT3 / VT3P) dominated but is phasing out Scattered performance issues all traits; even pyramids Resistance detected to all proteins, primarily Cry3Bb1 Cross-resistance documented with mCry3A (Agrisure)
and eCry3.1A (present in Duracade) Reports have decreased markedly, reflecting weather,
greater use of pyramids, and soil insecticides Resistance genes have not disappeared!
Status of Bt-RW Resistance
Bt-RW resistance confirmed for every trait but risk is not equal (Cry3Bb1>> mCry3A > Cry34/35Ab1, eCry3.1Ab ?)
Resistance is not complete; cross-resistance detected with all Cry3 proteins
Soil insecticide overlay 25% rotated corn, >50% continuous corn;
Insecticides cannot make up for a failing trait Seed industry shifting to pyramids of Bt-RW traits New traits probably not available until later this
decade
Corn Rootworms in Minnesota –Interplay of Resistance and Climate
Evaluating MN Populations for Bt-RW Resistance
• Two Plant Assays (seedling and greenhouse) and Diet Assay
Seedling - Relative Survival (Bt/Isoline) When Compared to RosemountPopulation Cry3Bb1 eCry3.1Ab Cry34/35Ab1 mCry3ARosemount Susceptible Susceptible N.S. SusceptibleCanby Resistant Resistant N.S. IntermediateHills Resistant Resistant N.S. ResistantBrookings, SD Susceptible Susceptible N.S. Susceptible
Greenhouse - Relative Survival (Bt/Isoline) When Compared to RosemountPopulation Cry3Bb1 eCry3.1Ab Cry34/35Ab1 mCry3ARosemount Susceptible N.S. N.S. SusceptibleCanby Intermediate N.S. N.S. SusceptibleHills Intermediate N.S. N.S. SusceptibleBrookings, SD Susceptible N.S. N.S. SusceptibleDennison Resistant N.S. N.S. Susceptible
Diet Toxicity Assay - LC50 μg/cm2 (95% C.I.)
Population Cry3Bb1 eCry3.1AbCry34/35Ab
1 mCry3ARosemount 16.2 (5.3-27.8) 0.8 (0.5-1.1) 0.9 (0.5-1.5) 0.7 (0.4-1.2)Canby 553.2 (278.8-3109.6) 9.7 (5.6-21.5) 4.1 (1.7-8.2) 11.9 (5.2-56.3)Hills 65.9 (22.4-133.7) 5.0 (2.9-9.7) 3.8 (2.4-5.6) 8.2 (4.3-22.3)Dennison 199.7 (82.0-1419843) 3.0 (1.9-5.5) 1.5 (1.0-2.1) 1.8 (1.2-2.6)Brookings 0 4 0 4 (0 2-0 6) 1 8 (1 1-2 6) 0 9 (0 6-1 3)
Cross-Resistance in Diet Bioassays
P=0.0233
Hills
Dennison
Canby
Brookings
Rosemount
P=0.0027
Hills
Dennison
Canby
Brookings
Rosemount
Rootworm Populations Dynamics: What’s Needed for Resistance
to Appear (or Re-appear)?
Resistance Genes Corn Trait
Exposure
Time = Density
Extended diapause problem fields re-emerged in 2015
WI Corn Rootworm Beetle Counts(WI Department of Agriculture)
0
0.5
1
1.5
2
2.5
3
3.5
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
Beetle/Plant N:W Ratio
YEAR
What’s the Prognosis forExtended Diapause Problems?
Remember: We’ll be dealing with eggs laid by 2014 corn rootworm beetles in rotated corn and by 2014-5 beetles in continuous corn!
Planting Date Effects on CRW Management
2.08
1.73
0.87
0.00
0.850.40
0.09 0.010.175 0.2450.005 0.010
0.0070.200
0.025 0.0200
0.5
1
1.5
2
2.5
115 124 138 151
Root
Inju
ry (I
owa
Stat
e Sc
ale)
Date of Planting (Julian Date)
RR RR+Force VT3 SSX
May 3 May 12 June 8May 26
Rosemount Research and Outreach Center - 2011
0
50
100
150
200
250
300
115 124 138 151
Adu
lt E
mer
genc
e (1
000'
s/ha
)
Date of Planting (Julian Date)
RR RR+Force VT3 SSX
2011 Planting Date and Efficacy
May 3 May 12 May 26 June 8
Planting Date Effects on CRW Management
A New Complication? Corn Rootworm Egglaying
Near RoundUp Ready® Volunteer Cornand Late-Season Resistance Weeds
Your Challenge:Control Weedy Grass Hosts
Early in Bt - RW Corn
0
20
40
60
80
100
120
Pre-emerge 2" 4" 8" None
Timing of Grass Removal
% R
oots
< 3
"
IsolineYieldGard RW
Stewardship critical: Keep early-season weedy grasses under control!
Corn Rootworms, Volunteer Corn and 2008 Corn Yield
Rosemount, MN
61.1
187.5 186.0176.7
163.8145.4
104.0
142.7
0
25
50
75
100
125
150
175
200
225
0 2,500 5,000 10,000Volunteer Corn Density (1000s/A)
Seas
onal
Cap
ture
s p
er T
rap
CRW Yield (bu/A) Western Corn Rootworms
0
1
2
3
4
5
6
7
8
7/11 7/21 7/31 8/10 8/20 8/30 9/9
Cap
ture
s/Tr
ap/D
ay 02,5005,00010,000
2007 Corn Rootworms, Volunteer Corn and 2008 Corn Yield
Rosemount, MNYield = 204.1 - 0.22 x Cumulative Stiucky Trap Count
R 2 = 0.501
100
125
150
175
200
225
0 50 100 150 200 250 300
2007 CRW Count Per Sticky Trap
2008
Cor
n Y
ield
0
1
2
3
4
5
6
7
8
9
7/23/2007 7/30/2007 8/7/2007 8/14/2007 8/21/2007
no volunteer corn volunteer corn (1875 ppa) volunteer corn (3750 ppa) vol. corn (7500 ppa)
Volunteer Corn Density and Northern Corn Rootworm Activity
Sticky Trap Captures per Day
Hints of Bt-RW Performance Issues Surfaced w/ Northern CRW in 2013
What about Bt-RW Trait Performance Against Northern Corn Rootworms?
How Well do Bt-RW Events Perform Against Northern Corn Rootworms?
Hybrid Family /
Event
Northern Corn RootwormRefugeHybrid
Refuge +Force 3G
Bt-RWHybrid
Bt-RW +Force 3G
DK 5263/5259
VT3
545 27749.2%
7885.7%
6787.7%
P37Y13/14 Herculex
Xtra
418 35116.2%
9477.5%
5686.6%
N40TAgrisure
297 304-2.4%
9269.0%
5282.5%
Sponsored by MN Corn Research & Promotion CouncilMN Legislative Rapid Agricultural Response Fund
Data represents sum of seasonal emergence from 16 traps covering 32 plants.
YieldGard IRM Considerations:Northern Corn Rootworm Emergence
0
10
20
30
40
50
60
70
80
90
100
7/3 7/10 7/17 7/24 7/31 8/7 8/14 8/21 8/28 9/4
Cum
ulat
ive
% E
mer
genc
e .
Refuge MalesYieldGard RW MalesRefuge FemalesYieldGard Females
242.2232.3
232.5227.3
How Well do Bt-RW Events Perform Against Northern Corn Rootworms?
297
418
545
0
100
200
300
400
500
600
DK 5259/5263 P37Y14/13 N40T
Bee
tles p
er c
age
Refuge HybridRefuge + Force 3G Bt-RW HybridBt-RW + Force 3G
49.2%*16.2%
-2.4%
85.7% 77.5% 69.0%
87.7% 86.6% 82.5%
*Efficacy expressed as % of emergence in refuge hybrid.
Comparative Efficacy of Bt - RW Events Against NCR
Design: Factorial combinations of 3 Bt-RW events (YieldGard VT3, Herculex Xtra, Agrisure) and their isolines from the same genetic family.
Soil insecticide: Force 3G only on both Bt-RW and non Bt-RW hybrids.
Seed treatment: Poncho 250 on all seed.
Traps: Placed in field July 2-3 with each covering two plants, 4 cages per plot, replicated 4 times.
Data collected: Beetles collected three times per week. Identified by species and sex.
Funding: Rapid Agricultural Response Fund, MN Corn Research & Promotion Council
Lodging under Different Corn Rootworm Management Strategies
0
5
10
15
20
25
30
35
St.Charles
LeSueur LakeMarion
Rose-mount
Lodg
ed P
lant
s (%
)
Herculex RW
NIR = 0.43
NIR = 1.16
NIR =2.36
NIR = 1.55
0
10
20
30
40
50
60
70
80
St.Charles
LeSueur LakeMarion
Rose-mount
Lodg
ed P
lant
s (%
)
YieldGard RWNIR =
0.84
NIR = 1.23
NIR =2.93
NIR = 1.59
Unprotected Aztec IF Bt-RW
Aztec and Bt-RW corn provided equal lodging protection!
Yield Response to Corn Rootworm Management
26.2
0.0
30.5
16.120.7
26.4
1.0
24.1
34.2
29.6
0
5
10
15
20
25
30
35
40
45
50
0 0.5 1 1.5 2 2.5 3Nodal Injury Rating (IA) .
Yie
ld A
dvan
tage
(bu/
A) Aztec IF YieldGard RW
Dekalb Hybrids – 2006
26.4
3.70.8
15.6
8.5
38.1
7.3
26.225.6
4.2
0
5
10
15
20
25
30
35
40
45
50
0 0.5 1 1.5 2 2.5 3Nodal Injury Rating (IA) .
Yie
ld A
dvan
tage
(bu/
A) Aztec IF Herculex RW
Pioneer Hybrids – 2006
Do farmers have a handle on their risk level?
Layer a Soil Insecticide?
RootProtectionStrategy!
Corn Root Protection: Insecticides
vs Bt-RW CornZone of
Root Protection forT-band Insecticides &
Seed Treatments
Zone of Root Protection
For Bt-RW Protein
Performance of Insecticide vs Bt-RW Traits:
Inse
ctic
ide
NIR
(IA
0-3)
Inse
ctic
ide
NIR
(IA
0-3)
Inse
ctic
ide
NIR
(IA
0-3)
Inse
ctic
ide
NIR
(IA
0-3)
Seed Treatment Soil Insecticides
Single Bt-RW Trait(+ Soil Insecticide)
Pyramid Bt-RW Trait(+ Soil Insecticide)
What about Insecticide Performance in MN Situations?
Soil Insecticide Overlay –Does it Protect More Roots?
18.02
9.2011.80 11.08
5.302.84 1.81 2.17 1.23 1.30 0.30
02468
101214161820
Root Protection from Corn Rootworm Management
Roots < 1.5”Roots 1.5 - 3”
Rosemount MN 2011
RR2 Refuge Herculex Xtra SmartStax
Soil Insecticide Overlays on Bt-Traits2015 Rosemount MN – Field I7
1.50a
0.63b
1.43a
0.29bc0.16cd
0.03d
1.27a
0.18cd
0
0.5
1
1.5
2
2.5
Nod
al In
jury
Rat
ing
(0-3
scal
e)
Management Option (Bt-RW Trait / Soil Insecticide)
NIR (<1.5") NIR (<3")
Soil Insecticide Overlays on Bt-Traits2015 Rosemount MN – Field I7
11.6b
94.7a
28.6b
98.7a 98.7a 100.0a
14.6b
94.7a
0
20
40
60
80
100
120
% C
onsi
sten
cy o
f Pro
tect
ion
(NIR
<0.2
5)
Management Option (Bt-RW Trait / Soil Insecticide)
Soil Insecticide Overlays on Bt-Traits2015 Rosemount MN – Field I7
174.4182.1
176189.9
199.3 190.1
129.4
165.2
100
120
140
160
180
200
220
Yie
ld (b
u/A
)
Management Option (Bt-RW Trait / Soil Insecticide)
Managing Bt-RW Performance Problems: Layering Insecticide on Traits (2012)
-22.1
-5.1 -3.1 -4.10.9
0.9-18.2
12.0
0.3 2.0 -4.1
4.0
0.65.6
12.0
-3.1
19.513.0
26.6
4.215.2
-30
-20
-10
0
10
20
30
40
VT3 HXX HXX RIB AM1 3000GT SSX SSX RIB
Yie
ld B
enef
it (b
u/A
)
Rosemount Harmony Severe Problems
Bt-RW Trait / Force 3G Performancein Cry3Bb1 Problem Field: Northfield MN
62.6
47.8
68.8
59.0
26.1
74.4 65.4
5.3
54.667.1
61.4
78.3
32.3
85.9 78.8
32.6
0
20
40
60
80
100
120
HXX HXX RIB SSX SSX RIB VT3 HXX AM1 3000GT
Yie
ld B
enef
it *(
bu/A
)
None Force 3GPreliminary Data
Soil Insecticides and Bt-RW Traits 2015 Rosemount MN
Trait InsecticideNodal Injury Rating
(<3”)Yield
(bu/A)Study #1 (Field D2)
None (RR2) None 1.07 177.7
Capture LFR 0.78 178.7
Force CS 0.66 194.3
Aztec 4.67G 0.45 217.0
L.S.D.
Study #2 (Field E)
Cry3Bb1 (VT3) None (RR2) 1.14 197.6
None 0.58 213.6
Capture LFR 0.16 213.7
Force CS 0.34 214.4
Aztec 4.67G 0.10 200.7
L.S.D.
Means followed by the same letter do not differ (p=0.05)
What to do? When “Simple” is Gone
KEY = IPM
Objective:Manage Corn Rootworm Populations!
2012 Problem Field – Springfield MN
VT TripleHerculex
Xtra
SmartStax Agrisure 3000GT
Photos by Bruce Potter
Dual Challenges:Trait Resistance &
Corn Rootworm Density
Trait Performance in Bt-RW Problem Field:Root Injury (Ostlie - Springfield MN)
22.8
19.9
8.9
25.8
20.4
14.9
24.9
18.5
25.4
18.8
13.4
0
5
10
15
20
25
30
# R
oots
Pru
ned
< 1.
5”
Preliminary Data
None Single PyramidBt-RW Trait(s)
Trait Performance in Bt-RW Problem Field:Beetle Emergence (Ostlie - Springfield MN)
743.0
459.0
283.0
1100.0
1630.0
463.0
1080.0
576.0
1680.0
421.0 432.0
0
250
500
750
1000
1250
1500
1750
2000
Bee
tles/
A (1
000s
)
Preliminary Data
None Single PyramidBt-RW Trait(s)
Trait Effect on Corn Rootworm Beetle Production: 2014-5 Springfield MN
156.6
559.2
18.6 25.999.1 91.3 56.0 72.3
0
250
500
750
1000
Bee
tles
(100
0s) p
er a
cre
Resistance Taking Us Back to School on the Basics
Reality Check on Rootworm TacticsControl Tactic Considerations
Crop Rotation Reduces pressure – watch variants, volunteer corn, weeds. Grain / forage demands (livestock), contracts (ethanol)
Pyramid traits Resistance ?; Performance may be partially compromised by prior trait use, refuge less effective, selection pressure continues, rotate to avoid resistance
Single traits Resistance confirmed (primarily VT3 / VT3 Pro). Cross-resistance w/ Agrisure, rotate to avoid resistance
Layer insecticide on refuge corn
Environmental/health issues, 40-60% kill, protection declines w/ pressure
Layer insecticide over pyramid
Masks resistance issues. Insurance use – benefit??? Depends on pressure, RIBs benefit under heavy pressure
Layer insecticide over single trait
Masks resistance issues. Benefit only under heavy pressure on refuge or if Bt-RW performance problem.
Spray beetles Reduces pressure, multiple sprays needed, scouting costs & challenges, fungicide tankmix??, environment concerns
CRW Management: What’s a Guy to Do?
This is a classic resistance situation => Be prepared to change management after 3-4 years in same trait.
Preferred option – Crop rotation!!!! Watch for rotational resistance with western corn rootworm!
If you can’t rotate, be prepared to invest more money in corn rootworm management Switch to different single trait or pyramid Layer with a soil insecticide (bandaid) Foliar sprays (multiple, well-timed) may be required to
knock-down heavy populations Get a handle on corn rootworm pressure and trait
performance => Scout! Take IPM (Integrated Population Management) approach
Western Corn Rootworm Injury to First-Year Bt-RW Corn (Gray - IL)
Any Questions?