soil insecticides, bt traits and corn rootworm

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")


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)



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

)


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?

soil insecticides, bt traits and corn rootworm

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