Nicholas P. Storer 

## DOW AGROSCIENCES APPROACHES TO RESISTANCE MANAGEMENT OF CORN ROOTWORM

- PROTECTION TRAITS

US EPA Scientific Advisory Panel on Corn Rootworm Resistance Monitoring for Bt corn

4

– 6 December 2013| 2 

### SmartStax ® 

### Anatomy



### MON 89034 x TC1507 x MON 88017 x DAS

- 59122

- 7

Cry1A.105 Cry2Ab2

Broad

- spectrum Lep Control

Dual Effective Dose (high dose) for corn borers Cry1F

PAT

Broad

- spectrum Lep Control High dose for corn borers

Glufosinate

ammonium tolerance Cry3Bb1

EPSPS

Corn rootworm Control Less than high dose Glyphosate tolerance Cry34/35Ab1

PAT

Corn rootworm Control Less than high dose

Glufosinate

ammonium tolerance 

# + =

*SmartStax ® , the SmartStax Logo, Roundup Ready ® , Genuity ® , VT Triple PRO ®

, YieldGard ® ,and YieldGard ® are trademarks of Monsanto Technology LLC. SmartStax ® multi

- event technology developed by Dow AgroSciences and Monsanto. Refuge Advanced ® and Herculex ® and the Dow Diamond are registered trademarks of The Dow Chemical Company (“Dow”) or an affiliated company of Dow. Herculex Insect Protection technology by Dow AgroSciences and Pioneer Hi

- Bred International, Inc.| 3 ● Bt corn is a powerful and convenient technology for managing important pests and protecting yield

● Pyramided products offer improved performance and robust durability

● Simplified refuge through seed blends promotes resistance management 

### Extended Durability; Simplified Refuge Management

Reduced

Refuge Blended Refuge| 4 Performance of corn rootworm protection traits over time

Hea vy rootworm pressure in areas with and without prior unexpected damage to Cry3Bb1 corn

0.0 0.5 1.0 1.5 2.0 2.5 3.0ISU Node Injury Scale (0-3) Iso

- genetic null hybrid Cry3Bb1 hybrid Cry34/35Ab1 hybrid (Herculex®) SmartStax® hybrid

2007

- 11 locations without reports of unexpected damage to 2012

- 13
locations with prior Cry3Bb1 or mCry3a unexpected damage 2012

- 13
locations without reports of unexpected damage to Cry3Bb1 corn| 5 

### Practical Definitions of Resistance

5 ● Laboratory resistance : a genetically

- mediated reduction in sensitivity of a target pest to Bt toxins, either in artificial diet or plant

- based bioassays

● Field resistance: a genetically

- mediated increase in the ability of a target pest to survive on Bt corn under field conditions

● Population resistance: occurs when a large portion of a pest population is field

- resistant and causes the Bt corn to fail to confer economic control of the population

 A population is a priori believed to contain individuals with resistance alleles. Identification of such individuals does not constitute identification of population resistance| 6 

### Response to Selection Pressure ≠ Population Resistance

Insects that were killed on Bt corn were on average more sensitive to the Bt protein than those that survivedProportionofpopulation

Bt tolerance Generation 0Proportion ofpopulation

Bt tolerance Generation 1

Depending on the heritability of survival

on Bt corn, the mean tolerance of the surviving population is greater than that of the original population

 We assume this happens to corn rootworms in every field of Bt corn
 We need to distinguish field

- relevant population resistance from simple response to directional selection| 7 

### Key considerations for field

- based monitoring

● Effective : High probability of detecting changes in populations that are expected to lead to changes in pest management (population resistance)

● Efficient : Avoid spending time and resources on enquiries that are not related to resistance

● Relevant : Detect emergence of field

- relevant population resistance, not simply selection pressure

● Adaptable : Continued experience with SmartStax and refuge

- in

- the

bag products should inform on

- going development of monitoring schemes

● Transparent : Key stakeholders kept informed where resistance may cause reduced performance

7| 8 

### Field resistance monitoring process

8 Performance Inquiry

• Trigger

• Immediate response

• Investigative Steps Unexpected Damage

• Trigger

• Immediate response

• Investigative Steps Suspected Resistance

• Trigger

• Remedial action

• Investigative Steps Confirmed Resistance

• Trigger

• Remedial action| 9 

### Customer Performance Inquiry

Customer, crop consultant, extension agent etc contacts Dow rep with a concern about the performance of Bt corn product

Visit relevant field(s) to assess damage and investigate causes

Confirm presence of Bt trait(s) and planting layout (ELISA tests, planting records)

Determine if crop damage meets “Unexpected Damage” definition

Recommend rootworm best management practices| 10 

### Unexpected Damage

1. Is the field planted to Dow’s Herculex ® or SmartStax ® product? (planting records, ELISA strip tests)

2. Is lodging > 25% of plants in an area of the field > 1 acre?

3. Is the damage caused by corn rootworm larval feeding?

4. Is the nodal injury score > ≈ 0.5

– ≈0.75* on at least six of ten roots dug from arbitrarily chosen lodged plants in the affected area?

5. For blended refuge (RIB) products, are the damaged plants SSX (not refuge plants) and are they non

- adjacent to refuge plants? “Unexpected Damage ” if is YES to all of these

Lower end of the range is used in conditions that lead to lower expected damage; higher end is used in conditions that lead to higher expected feeding damage.| 11 

### Investigations into Unexpected Damage



### Sample 5 plants from each of at least 3 additional areas in the field to determine extent of damage Collect healthy plant tissue (if available ) for quantitative ELISA Collect adult corn rootworm beetles (if available) for bioassay Bioassay progeny (after diapause) using standard laboratory techniques Recommend grower implements additional rootworm management the following year

Review CRW management practices the following year| 12 

### Suspected Resistance 

## Suspected Resistance is defined as

● Unexpected Damage (if tissue available for testing, confirmed to express CRW proteins at the normal level),

and

● Insects show significantly different response from baseline/controls in bioassay;| 13 

### Response to Suspected Resistance

• Emphasis on crop rotation

• Use of an additional rootworm control tool in combination with or in place of SmartStax (e.g. soil insecticide, chemigation , seed

- applied insecticide, adulticide

, alternative CRW trait)

• Follow up in the following year to assess the success of the remedial actions in terms of insect susceptibility and product performance 

### Recommend alternative corn rootworm management

• Change in response is heritable and provides selective advantage

• Change in response is sufficiently high to cause economic root injury 

### Investigations to confirm resistance| 14 

### Confirmed Resistance

● Confirmed Resistance is defined as

 Heritable significant change in response to Bt proteins in bioassay leading to increased survival to adult and

 Change in response is sufficiently high to cause economic root injury and

 Population persists in the field causing reduced product performance

● Affected area determined by geographic extent of nearby Unexpected Damage cases| 15 

### Responses to Confirmed Resistance


## Inform stakeholders in affected area, including growers, extension, crop consultants etc

Follow best IPM practice recommendations to manage corn rootworms in the affected area

Continue to monitor in the area for changes in resistance levels

Transition from proactive IRM to IPM in the presence of resistance| 16 Process Overview

Performance Inquiry

• Recommend CRW

best management practices

• Investigate extent

of lodging, root injury

• Damage is greater

than expected? yes Unexpected Damage

• Recommend

additional CRW management tools

• Quantitative ELISA

on plant tissue, Bioassay rootworm collection

• Population is less

susceptible than normal? yes Suspected Resistance

• Recommend

alternative CRW management tools

• Characterize

rootworm survival and damage to SmartStax

• Reduced

susceptibility is heritable and damaging? yes Confirmed Resistance

• Implement IPM

program for the resistant population

• On

- going research

to understand resistance genetics and biology, monitoring

• Monitor for

changes in resistance levels

Investigation Complete
On

- going communication with the grower about performance of SmartStax and rootwormnonono