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 2/13/2024

Reduced Corn Rootworm Adult Emergence With RNAi

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Harvest corn kernels in a pile.

Agronomy Research Update
Written by Jim Bing, Tim Nowatzki, Tim Mabry, Jeff Klever, and Mark Jeschke, Pioneer Agronomy Sciences.

Key Findings

  • Trials were conducted in fields with high corn rootworm pressure to evaluate the impact of corn rootworm traits on emergence of rootworm adults from the soil.
  • The corn rootworm traits in Qrome® corn and Vorceed™ Enlist® corn reduced emergence of western corn rootworm beetles by 71% and 92%, respectively.
  • The addition of RNAi technology in the Vorceed Enlist trait package provided a significant advantage in managing adult emergence.

Related Articles

A New Corn Rootworm Management Tool

  • Ribonucleic acid interference (RNAi) technology has been commercialized to provide an additional unique mode of action for protection against corn rootworm and is available in Corteva Agriscience seed brands in Vorceed™ Enlist® corn.

    Vorceed Enlist corn contains three modes of action for protection against corn rootworm

    Figure 1. Vorceed Enlist corn contains three modes of action for protection against corn rootworm.

Study Description

  • Field experiments were conducted in 2022 to evaluate efficacy of the corn rootworm traits in Qrome corn and Vorceed Enlist corn for reducing adult emergence.
  • Experiments were conducted at six locations with natural infestations of western and northern corn rootworm.
  • Study locations were specifically targeted to fields with a history of high corn rootworm pressure that were located in regions with previously reported performance issues with Bt rootworm traits.
  • Adult emergence was quantified using single-plant emergence cages (Figure 2).

Table 1. Corn rootworm treatments compared in 2020, 2021, and 2022 field experiments.

Treatment Description CRW Traits
 Insecticide Seed
Treatment Rate
(clothianidin)

Unprotected Check

none

250 IST

CRW Traits in Qrome
+ 1250 rate IST

Cry34/35Ab1

MCry3A

1250 IST

CRW traits in
Vorceed Enlist

Cry34/35Ab1

Cry3Bb1

DvSnf7

250 IST

CRW traits in
Vorceed Enlist
+ 1250 rate IST

Cry34/35Ab1

Cry3Bb1

DvSnf7

1250 IST

Emergence cage used to capture corn rootworm adults emerging from the soil

Figure 2. Emergence cage used to capture corn rootworm adults emerging from the soil.

Results

  • Corn rootworm pressure was high at the study locations in 2022 – the average node injury score in the unprotected checks was 1.99 on a 0-3 scale (Figure 3).
  • The corn rootworm traits in Vorceed Enlist corn and Qrome corn + 1250 rate IST both provided effective protection of corn roots against corn rootworm damage.
  • The corn rootworm traits in Vorceed Enlist corn and Qrome corn + 1250 rate IST both significantly reduced emergence of western corn rootworm compared to the unprotected check (Figure 3).

    Western corn rootworm adult emergence - beetles per plant

    Figure 3. Western corn rootworm adult emergence (beetles/plant). Bars and values with the same letter are not significantly different at α = 0.05. Click here or on the image above for a larger view.

  • The addition of RNAi technology in the Vorceed™ Enlist® trait package provided a significant advantage in controlling adult emergence.
  • The corn rootworm traits in Qrome® corn + 1250 rate IST reduced adult emergence by 71%, which is lower than would generally be expected over a larger range of environments and is reflective of the high rootworm pressure conditions that were specifically targeted for this study.
  • Results of this study demonstrate the additional value provided by the RNAi technology in the Vorceed Enlist trait package for reducing adult emergence under the most extreme corn rootworm pressure conditions.

Management Considerations

  • Corn rootworm challenges are localized and need to be managed on a field-by-field basis with a proactive, multi-year approach that employs multiple tactics to maintain low corn rootworm populations in the field.
  • Historically, the use of crop rotation and insecticidal sprays targeting corn rootworm adult beetles have been the primary tactics growers could use to lower corn rootworm populations in fields.
  • The RNAi technology in the Vorceed Enlist trait package provides another effective tool for managing the density of corn rootworm populations in fields in addition to protecting roots.
  • Use of Vorceed Enlist corn along with in-season beetle scouting should allow for the effective use of pyramided Bt rootworm products (without the RNAi trait) or non-rootworm corn treated with soil insecticide as options in the field in the subsequent season, extending the life of the RNAi technology.

Video - Western Corn Rootworm Variant and Northern Corn Rootworm

Western corn rootworm and northern corn rootworm are serious threats to corn yield. This video looks at what risk factors are associated with high CRW populations.

Corn Rootworm Best Management Practices

1. Plant the Required Refuge

2. Rotate Crops

  • Rotate at least every 3rd year in the following scenarios:
    • In long-term continuous corn system
    • CRW populations are high
    • Experiencing problems with CRW trait performance
  • In areas where rotational-resistant CRW variants exist, CRW management options may be needed the following year.

3. Rotate Traits

  • Use Bt hybrids with multiple modes of action for CRW control whenever possible.
  • Use a non-Bt-traited hybrid with insecticide.

Manage CRW With Insecticides

  • Adult CRW management considerations:
    • Scout fields for CRW adults during silking stage, as CRW adults feed on corn silks and may reduce yield.
    • Foliar sprays may be an option if CRW beetle populations reach an economic threshold for damage.
    • Follow university extension or local crop consultant recommendations for products, rates, and proper timing of adult spray applications for reducing CRW beetle populations.
  • Larval CRW management considerations:
    • Soil-applied insecticides are not recommended for control of CRW in Bt-traited corn hybrids except under limited circumstances.
    • Consult with extension, crop consultants or other local experts for recommendations when considering a combination of CRW traits and soil applied insecticides.
    • Soil-applied insecticides should not be necessary for CRW control with pyramided CRW-traited Bt corn hybrids.


Qrome corn   Vorceed Enlist   LibertyLInk  AgrisureRW

Agrisure® is a registered trademark of, and used under license from, a Syngenta Group Company. Agrisure® technology incorporated into these seeds is commercialized under a license from Syngenta Crop Protection AG. Roundup Ready® is a registered trademark used under license from Monsanto Company. Liberty®, LibertyLink® and the Water Droplet Design are trademarks of BASF.

The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. 2022 data are based on average of all comparisons made in 6 locations through Dec 1, 2022. Multi-year and multi-location is a better predictor of future performance. Do not use these or any other data from a limited number of trials as a significant factor in product selection. Product responses are variable and subject to a variety of environmental, disease, and pest pressures. Individual results may vary.

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