Value of Multiple Modes of Action for Corn Rootworm Control

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 resistance can allow growers to help protect their corn yield potential while significantly reducing their reliance on SAI and foliar applied insecticides (FAI), particularly with multiple MOA B.t.

Insecticide Safety

Insecticides come with safety issues. Not only can they be toxic to their direct users, but they can be toxic to others coming into contact with the insecticide. Wildlife can also be negatively affected. Corn products protected with B.t. traits may reduce reliance on insecticides, thereby minimizing the hazards associated with 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 the Genuity® brand provides corn products with multiple MOA protection for belowground corn rootworm and aboveground corn earworm insect protection through the use of Genuity® SmartStax® technology products. Genuity® 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 competitive CRW single MOA products for which the use of an SAI is recommended.


In efforts to define the value and CRW efficacy provided by Genuity® SmartStax® technology products 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, Genuity® SmartStax® technology products 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 (WCR) and northern corn rootworm (NCR) 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, rotation is no longer as effective in specific areas of the Corn Belt due to extended diapause populations of NCR and the soybean variant of WCR.
  • Seeds with multiple MOA, such as Genuity® SmartStax® technology products have proven to be a consistent CRW control tool.
  • Soil-applied insecticides labeled for control of CRW larvae can be applied at planting with conventional seed products and along with single MOA B.t. seed products to add another MOA.

Additional Considerations:
Regardless of high or low rootworm pressure, Genuity® SmartStax® technology products 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.
  • Genuity® SmartStax® technology products offer earworm B.t. protection. Lost yield attributable to earworm feeding can be as high as 7%.4
  • Genuity® SmartStax® technology products 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 Genuity® SmartStax® RIB Complete® Corn Products are available, market research showed that famers place a value of $5/acre on refuge-in-the-bag products.6

Genuity® Rootworm Manager App

iPad® device users can download an app that allows farmers to complete assessments on each field to determine the potential risk of corn rootworm damage. The tool follows proven pest management recommendations for scouting, crop rotation, utilizing multiple MOA when planting, and suggesting specific insecticides based on crop type. The app also allows growers to take notes, access scouting reports, set alerts, and share results by email. The app can be downloaded from or the iTunes® App Store.

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 (2010-2013).
4 Boyd, M.L. and W.C. Bailey. 2001. Corn earworm in Missouri. MU Guide, G 7110. University of Missouri-Columbia. (verified 10/1714).
5 2011 and 2012 Internal Monsanto Commercial Field Trials.
6 2011 Market probe farmer quantitative study.For additional agronomic information, please contact your local seed representative.