CRW Management: Fact or Fiction?

Pioneer agronomists and researchers dig up the truth on common CRW myths.

Northern and western corn rootworm beetles


Why is corn rootworm such a perennial problem?

Of all the pests that threaten corn yields, none have the seemingly infinite capability to adapt and overcome management strategies that corn rootworm (CRW) has displayed. These adaptations are how CRW continues to cause over a billion dollars in damage yearly across the US.

1. CRW has adapted to overcome crop rotation

Illustration - CRW has adapted to overcome crop rotation

Rootworms’ ability to evolve has made crop rotation ineffective in many areas. The soybean variant western corn rootworm has evolved to lay eggs in non-corn fields. The northern corn rootworm has shown extended diapause, in which eggs remain viable in the soil for several years before hatching.

2. Damaged roots are a gateway to other yield threats

Illustration - Damaged roots are a gateway to other yield threats

Plants with damaged root systems are more susceptible to drought stress and lodging, meaning rootworm damage is a gateway to a host of additional yield threats.

3. CRW damages corn during its whole lifecycle

Illustration - CRW damages corn during its whole lifecycle

Rootworm larvae AND adults cause severe problems, which means potential issues all season long. Adult CRW feeding on corn silks during pollination can cause poor seed set and subsequent yield loss.

4. CRW have evolved with technology

Illustration - CRW have evolved with technology

Resistant corn rootworm populations have now been documented for all four commercially available Bt proteins for CRW control.

Your Top CRW Questions Answered

Agronomist and customer in cornfield - midseason

Why should I scout for CRW if traits are protecting the corn?

No solution is foolproof, and CRW will surprise you. Root digs and sticky traps can determine rootworm pressure (when done right) and help you make the best decision.

Scouting for CRW Larvae & Beetles

Root digs for larvae scouting will help in-season to determine if a response is needed. Sticky traps can be used to estimate adult CRW populations, a crucial warning for next year’s populations.

Don’t assume pressure is uniform

CRW pressure varies field-to-field and can significantly vary within a field.

Use root digs early to spot larvae

Scouting should begin in early to mid-June or when corn is between V6 to V12. Dig up 2 plants at each of 5 locations within the soil from 6” to 8" around the plant and sift soil over a sheet of black plastic, looking for 1/32” to ½” long larvae.

We dig so you don’t have to.

Corteva research digs tens of thousands of roots every year in the most challenging CRW environments we can find to test how the industry’s traits are holding up.

Beetles in sticky traps have already laid the next season’s yield robbers

Sticky traps are good for field-to-field observations and will help you make a better-informed decision on next seasons management options. But don’t use sticky traps for hybrid-to-hybrid population comparisons as CRW can move up to a ½ mile radius and come from another location.


Is there really not a "plant it and forget" solution for CRW management?

Unfortunately, only limited CRW trait technologies exist, and many seed brands use the same ones. While the latest addition, new RNAi technology is exciting, it’s not a standalone solution to the full problem.

Bt Traits & RNAi Technology

Different hybrids might have the same Bt trait

Many seed brands use the same CRW traits. Simply switching brands does not necessarily mean switching to different Bt traits.

Genetics still matter

The bigger difference from seed brands comes from the genetics of the hybrids, like yield potential, root strength or disease tolerance.

RNAi takes time to kill CRW

The RNAi trait can take up to 12 days to kill CRW, a window in which large amounts of feeding damage can still occur. Stacking RNAi technology with other CRW traits that act immediately, including Bt traits with the Cry34/35 protein, helps eliminate this gap.

CRW best management practices should still be followed

An integrated approach to CRW management will always be the most successful. These include industry best practices like crop rotation, suppressing larval development, insecticides and more.

Photo - field operation - aerial view

Do I have to give up key agronomic traits or yield potential to get the CRW traits I need?

No! With limited traits to combat CRW, it’s important to not lose sight of the advantages from powerful agronomic traits and excellent yield potential. There’s no need to sacrifice hybrid performance for CRW protection, you can have both.

Strong agronomics are key to overall performance

CRW traits are important for root health on high pressure CRW acres, but they’re not the full story. High yield potential and strong agronomic traits like native root strength and disease tolerance play critical roles in overall plant health.

1. 6-8 bu/A yield advantage

Pioneer® brand Qrome® products have averaged a 6-8 bu/A yield advantage* over competitive products with SmartStax® technology for the last three years.

2. An evolution in Cry 34/35 protection

Pioneer® brand Qrome® products contain a different version/event of the Bt protein Cry 34/35 compared to other products in the industry (SmartStax, AMXT).

3. Bred for agronomics + protection

This version has opened up a wider germplasm funnel for our breedings, leading to more product options with key agronomic traits and CRW trait protection.

Logo - Qrome Products

*Data is based on the average of comparisons made in the US 2019-2021. Comparisons are against all competitors, technology segment matched, unless otherwise stated, and within a +/- 3 CRM of the competitive brand. Efficacy from multiple trials with moderate & high CRW pressure at 8 locations in 2014, 6 locations in 2015, 8 locations in 2016, 8 locations in 2017, 10 locations in 2018, 9 locations in 2019, and 15 locations in 2020.