Managing Corn Rootworm

• Corn rootworm (CRW) has adapted to decades of management strategies and continues to be destructive.
• Duracade™ trait adds a different tool to the toolbox for rootworm management.
• Diversity in management practices is key for long-term success in managing CRW.

Corn rootworm is the most destructive corn pest in the United States and costs growers more than $1 billion annually in reduced grain yield and control measures. Larvae feed on roots, resulting in underdeveloped root systems, reduced nutrient uptake, weak brace roots and lodged corn (Figure 1). Adult CRW beetles can also interfere with pollination by feeding on pollen and clipping silks, resulting in poor ear fill, and lay eggs in the soil that endanger future corn crops.

Corn rootworm is a difficult pest to manage, to the point that repeated use of the same single management practice will eventually end in disappointment. There is no silver bullet for corn rootworm, but smart planning and hybrid selection are key to building a sustainable, multi-year management plan. Developing a multi-year, field-by-field corn rootworm management plan utilizing different control methods in different years is an important part of addressing one of the most damaging insect pests to corn and ensuring hybrids reach their full yield potential. Understanding if CRW is currently present in fields through scouting or beetle trapping is an important first step in developing management plans. Once the relative risk of CRW is understood, the following management options can be considered independently or in combination as part of a multi-year integrated management plan:

• Crop Rotation: Rotate to non-host crops like soybeans to break up CRW’s normal lifecycle.  Adapted variants of CRW, known as western CRW variant or northern CRW with extended diapause, have changed their lifecycles to overcome single-year rotation (Figure 2).  Be aware if present locally and its impact on rotation effectiveness.
• Dual mode of action CRW traits: Use different CRW traits like Duracade and Agrisure^® Total trait stacks that have more than one CRW trait.
• Soil-applied insecticides like Force^® for larvae control.
• Foliar-applied insecticides like Warrior II with Zeon Technology^® for adult beetles to minimize silk clipping and reduce egg laying.

Plans should include the use of different corn rootworm control methods in different years to help minimize the adaptation of corn rootworm to one technology. The plan may need to change each season, depending on pressure, but having it in place gives growers a head start. 

The Duracade trait, the most recently registered Bacillus thuringiensis CRW trait, expresses a protein that binds differently in the gut of CRW than any other trait on the market. Additionally, it is always stacked with a second mode of action against CRW, making it a good tool for managing CRW (Figure 3). Agronomy In Action research trials have evaluated the effectiveness of Duracade across multiple years and demonstrated improved root protection (Graph 1) and yield (Graph 2) when used alone or in combination with soil-applied insecticides across many different pest levels.

Select Golden Harvest^® Duracade hybrids are now available treated with CruiserMaxx^® Corn 1250 seed treatment for additional root protection. Corn rootworm trials across 7 locations showed reduced feeding damage at most sites (Graph 3). Whether trying to protect yield or preserve effectiveness of current management practices, effective CRW management will require the integration of multiple control practices, not a singular technology.

Managing Low Pressure Corn Rootworm

If little to no previous signs of larval feeding or adult beetle populations have been observed and planting corn is selected for areas with western CRW variant, northern CRW extended diapause or corn following corn, consider using at least one of following management practices:

1. Multiple mode of action CRW traited hybrids
2. Non-CRW traited hybrid with Force soil insecticide

If planting first-year corn in areas where CRW has not yet been known to have adapted to corn rotation management, consider using a non-CRW traited hybrid, such as an Viptera™ traited hybrid, that provides broad-spectrum control of above-ground pests. If other soil insects are present, consider adding Force soil insecticide.

Options for Managing Heavy Corn Rootworm Pressure

1. Crop rotation: Breaking up CRW cycle by rotating to non-host crops, such as soybeans, in fields with a history of high CRW presence or injury should be considered.
2. Traited corn hybrids: 
   1. If NO history of root injury on traited hybrids:
      1. Use hybrids with multiple CRW traits
      2. Scout and consider beetle control with a foliar insecticide to minimize silk clipping and reduce female egg laying
   2. If there is a history of feeding damage to traited hybrid and unable to rotate, use combination of:
      1. Hybrids with multiple CRW traits
      2. Soil-applied insecticide with traits
      3. Scout and consider beetle control with a foliar insecticide.
      4. Seed treatment insecticides

Long-term corn rootworm management requires a multi-year, whole-farm approach. There is an important balance between CRW control, yield protection and resistance management. It is not a one-size-fits-all approach. Effective CRW management will require the integration of multiple control measures, not a singular technology.

Example of a Multi-Year Corn Rootworm Management Plan