Value of Multiple Modes of Action for Corn Rootworm Control

Corn product selection is one of the most important decisions made to maximize yield potential.
  • SmartStax® Corn technology provides corn products with multiple modes of action (MOA) protection for belowground corn rootworm (CRW) and aboveground corn earworm (CEW) insect protection.
  • A soil applied insecticide (SAI) is recommended to be used with single MOA insect protection products.
  • In moderate to high corn rootworm pressure situations, SmartStax® technology provided an average advantage of 20+ bu/acre over non-rootworm B.t. protected corn products without an SAI and 8 bu/acre over single MOA products without an SAI.

Importance of Corn Product Selection

Selecting corn products each year is one of the most important decisions made toward maximizing yield potential. Products should be selected based on the environment in which the product will be grown. The environment not only includes weather, but pressure from disease and insects. Stress from weather, with the exception of irrigation, cannot be controlled; however, products can be selected for tolerance to heat and drought. Likewise, products can be selected with varying degrees of tolerance or resistance to certain diseases. Selecting products with Bacillus thuringiensis (B.t.) insect traits can allow growers to help protect their corn yield potential while significantly reducing their reliance on soil applied insecticides (SAI) and foliar applied insecticides (FAI), particularly with multiple modes of action (MOA) B.t. protection.

Insecticide Safety Considerations

Insecticides can be an effective means of controlling insects.  However, they can have specific safety requirements.  As examples, these requirements may include personal protective equipment for applicators and re-entry restrictions for the applied area. 

Insecticides may negatively affect beneficial insects and other non-target organisms.  Corn products protected with B.t. traits may reduce reliance on insecticides, thereby minimizing the negative aspects of their use.

B.t. Protection

With lower commodity prices, consideration may be given to selecting corn products without B.t. protection to save on seed costs. However, selecting non-B.t. protected products exposes growers to the risk of lost yield potential due to insect activity (Figure 1) and insecticide safety concerns.1 The cost of an SAI can also be about $16/acre.



Corn products with B.t. protection can be divided into those with belowground protection, those with aboveground protection, or both. Within those protections, above- and belowground protection can be accomplished with either single or multiple MOA protection. However, only products with SmartStax® technology have multiple MOA protection for belowground corn rootworm (CRW) and aboveground corn earworm (CEW) insect protection. SmartStax® RIB Complete® Corn Blend Products are refuge-in-the-bag products, making refuge compliance automatic in the Corn-Growing Area. In the Cotton-Growing Area, an additional structured refuge is required.

Soil insecticides are recommended for use with single MOA belowground B.t. products to add an additional MOA for CRW protection. Safety issues discussed earlier come with the use of an SAI. Table 1 lists CRW single MOA products for which the use of an SAI is recommended.




In efforts to define the value and CRW efficacy provided by products with SmartStax® technology compared to single MOA products, Monsanto Technology Development Representatives conducted CRW control studies in 2012 and 2013 in ten states. All products were adapted for the testing area, had their respective seed treatments, and contained required CRW refuge seed within the seed bag. 

Results and Discussion

In moderate to high CRW pressure situations, products with SmartStax® technology provided an average advantage of over 20 bu/acre compared to non-rootworm B.t. protected corn products without an SAI and 8 bu/acre over single MOA products without an SAI (Figure 1).

Importance of Controlling Corn Rootworm Larvae

Historical estimates suggest western corn rootworm (WCRW) and northern corn rootworm (NCRW) are responsible for nearly 1 billion dollars annually in crop losses and control costs.2 Larval feeding can decrease yield potential and increase the risk of root lodging. Although the average yield advantage is over 20 bu/acre, data show there can be an even greater impact of up to 80 bu/acre yield loss due to CRW.3 Predicting the extent of CRW damage is very difficult, but the potential for damaging populations is more probable under certain circumstances.

Practices That Can Increase CRW Pressure

In all areas of the Corn Belt, production practices that favor growth in CRW populations include: long-term corn rotations, late-planted fields, and/or planting of late-maturing products. For example, full season products used by many silage growers are often prime targets for escalating CRW beetle populations because they pollinate when other desirable adult CRW food sources have deteriorated.

Management Options

  • Crop rotation has been and continues to be a recommended method to effectively control CRW larvae. However, crop rotation is no longer as effective in specific areas of the Corn Belt due to extended diapause populations of NCRW and the soybean variant of WCRW.
  • Seeds with multiple MOA, such as products with SmartStax® Corn technology have proven to be a consistent CRW control tool.
  • If rotation or SmartStax®RIB Complete®Corn Blend products are not acceptable options, consider using soil-applied insecticides in combination with corn products that do not provide B.t. protection from CRW. 
  • Due to resistance concerns, planting single-mode-of-action technologies such as VT Triple PRO® products or VT Triple PRO® RIB Complete® Corn Blend products is not recommended when less than satisfactory control of CRW has been observed.

Additional Considerations:
Regardless of high or low CRW pressure, products with SmartStax® technology can provide growers a better opportunity to maintain and increase profitability through their consistent CRW protection. Along with the $16/acre cost for an SAI, consideration should be given to:

  • Soil-applied insecticides are relatively insoluble and protection is limited to a relatively small portion of the root zone.
  • The consistency of performance of SAIs can be highly dependent on environmental conditions.
  • Products with SmartStax® Corn technology offer CEW B.t. protection. Lost yield attributable to CEW feeding can be as high as 7%.4
  • Products with SmartStax® Corn technology are treated with Acceleron® Corn Seed Treatment Products plus Poncho® 500/VOTiVO® seed treatment, which has shown an increased yield potential of 3.7 bu/acre over other basic seed treatments.5
  • In the Corn-Growing Area where SmartStax® RIB Complete® Corn Blend Products are available, market research showed that farmers place a value of $5/acre on refuge-in-the-bag products.6


1 Technology Development Sites in IL, IA, KS, CO, NE, WI, MI, IN, MN, SD (2012-2013).

2 Croff, C.D. and P.D. Mitchell. 2007. When does it pay to plant RW Bt corn in Wisconsin? Proceedings of the 2007 Wisconsin Fertilizer, Aglime & Pest Management Conference,
Vol. 46.

3 Technology Development Sites in IL, IA, KS, CO, NE, WI, MI, IN, MN, SD, OH, DE

4 Boyd, M.L. and W.C.  Bailey. 2001. Corn earworm in Missouri. MU Guide, G 7110. University of Missouri-Columbia.

5 2011 and 2012 Internal Monsanto Commercial Field Trials.

6 2011 Market probe farmer quantitative study.

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