Value of Multiple Modes of Action for Corn Rootworm Control

  • SmartStax® Corn technology provides corn products with multiple MOA protection for belowground corn rootworm (CRW) and aboveground corn earworm (CEW) insect protection.
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  • A soil applied insecticide (SAI) is recommended to be used with single MOA insect protection products.
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  • In moderate to high corn rootworm pressure situations, SmartStax® Corn 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.
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Importance of Corn Product Selection

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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 the 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.

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Insecticide Safety Considerations

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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.

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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.

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B.t. Protection

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Figure 1

Figure 1. Expected Yield Over the Long-Term

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SAI = Soil-Applied Insecticide. TD Sites in IL, IA, KS, CO, NE, WI, MI, IN, MN, SD (2012-2013)100-112 RM; N = 31 protocol site years under moderate and high CRW pressure. *Moderate Pressure = locations where untreated check had an average Nodal Injury Score (NIS) of > 0.5-1.0; High Pressure = locations where untreated check had an average NIS of > 1.0.

 

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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 expose growers to the risk of lost yield potential due to insect activity (Figure 1) and insecticide safety concerns.1 The cost of a SAI can also be about $16/acre.

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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. SmartStax® Corn technology provides corn products with 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.
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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 a SAI. Table 1 lists CRW single MOA products for which the use of a SAI is recommended.

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 Table 1. Largest Volume Trait B.t. Products for Corn Rootworm/Earworm Protection 
 Products with the Following Technology
 Abbreviation
Modes of Action for Control of Corn Rootworm/Earworm
 SmartStax® 
 
 Two/Two
 Genuity® VT Triple PRO® 
 
 One/Two
 Optimum® AcreMax® Xtra
 AMX
 One/X*
 Optimum® AcreMax®1
 AM1
 One/X
 Agrisure® 3000GT
 3000GT
 One/X
 Herculex® XTRA
 XR or HXX
 One/X
 Optimum® Intrasect® Xtra
 YXR
 One/X
 Optimum® TRIsect®
 CHR
 One/X
 Optimum® AcreMax® TRIsect®
 AMT
 One/X
*X = Suppression 
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Research

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In efforts to define the value and CRW efficacy provided by products with SmartStax® Corn 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.

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Results and Discussion

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

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Importance of Controlling Corn Rootworm Larvae

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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.

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Practices That Can Increase CRW Pressure

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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.

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Management Options

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  • 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 ofWCRW.
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  • Seeds with multiple MOA, such as products with SmartStax® Corn technology have proven to be a consistent CRW control tool.
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  • 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.  
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  • Due to resistance concerns, planting single-mode-of-action technologies such as Genuity® VT Triple PRO® products or Genuity® VT Triple PRO® RIB Complete® Corn Blend products is not recommended when less than satisfactory control of CRW has been observed.
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Additional Considerations:
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Regardless of high or low CRW pressure, products with SmartStax® Corn technology can provide growers a better opportunity to maintain and increase profitability through their consistent CRW protection. Along with the $16/acre cost for a  SAI, consideration should be given to:
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  • Soil-applied insecticides are relatively insoluble and protection is limited to a relatively small portion of the root zone.
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  • The consistency of performance of SAIs can be highly dependent one environmental conditions.
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  • Products with SmartStax® Corn technology offer CEW B.t. protection. Lost yield attributable to CEW feeding can be as high as 7%.4
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  • Products with SmartStax® Corn technology are treated with Acceleron® Seed Applied Solutions plus Poncho®/VOTiVO® with clothianidin at 500 mg/kg rate, which has shown an increased yield potential of 3.7 bu/acre over other basic seed treatments.5
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  • 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
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Genuity Rootworm Manager App

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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 by accessing http://www.Genuity.com/RootwormManager and then selecting Get the App or by visiting the iTunes® Store from your iPad®.