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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.1 Corn rootworm (CRW) larval feeding on roots can decrease yield potential and increase the risk of root lodging (Figure 1). Although the average yield advantage is 20 bu/acre, data shows there can be an even greater impact of up to 80 bu/acre yield loss due to CRW.2 Predicting the extent of CRW damage is very difficult, but the potential for damaging populations is more probable under certain circumstances.
Production practices that favor growth in CRW populations include long-term corn rotations, late-planted fields, and/or the planting of late-maturing corn products for the area. For example, full season products used by many silage growers are often prime targets for CRW beetles because pollination occurs when other desirable adult CRW food sources have diminished.
In efforts to define the value provided by B.t. traits and SAI's, Monsanto Technology Development Representatives conducted CRW control studies from 2010 to 2013 in twelve states to evaluate the CRW protection efficacy of Genuity SmartStax RIB Complete Corn Blend products compared to similar corn products without B.t. CRW protection.
All products were adapted to the testing area and had their respective seed treatments. Nodal injury scores (NIS) and yield data were collected from the studies.
In Moderate to High-Pressure Situations2 - Genuity SmartStax RIB Complete Corn Blend products provided an average advantage of 20 bu/acre over non-CRW B.t. protected corn products (Figure 2). When an SAI was used with non-CRW B.t. protected products, there was a 10 bu/acre average advantage for Genuity SmartStax RIB Complete Corn Blend products (Figure 2). Genuity SmartStax RIB Complete Corn Blend products had an NIS of 0.29 compared to scores of 0.58 and 1.46 for non-CRW B.t. protected products with and without an SAI respectively (Figure 3). An SAI would add about $16/acre to the cost of production and should be considered when selecting seed products.
In Low-Pressure Situations2 - Genuity Smartstax RIB Complete Corn Blend products provided an 8 bu/acre average advantage over non -CRW B.t. products that did not have an SAI.4 If farmers determine they have a low risk of damage from a CRW infestation, and decide to plant a non-CRW B.t. product without an insecticide, an average 8 bu/acre in yield potential could be lost. The use of an SAI with non-CRW B.t. products may provide adequate levels of CRW control in instances of low pressure. However, due to the difficulty of predicting damage levels, growers run an exceptional risk of underestimating damage potential; thereby, incurring a substantial loss in yield. In the short-term, growers may realize modest cost savings. However, the use of non-CRW B.t. products alone or with an SAI will likely cost growers more in the long-term.
Regardless of high or low CRW pressure, Genuity® SmartStax® RIB Complete® Corn Blend products can provide growers a better opportunity to maintain and increase profitability. Along with the $16/acre cost for an SAI, consideration should be given to:
iPad® device users can download an app that allows farmers to complete assessments in each field to determine the potential risk of CRW damage. The tool follows proven pest management recommendations for scouting, crop rotation, utilizing dual MOA when planting, and suggesting specific insecticides based on the crop type. The app also allows farmers to take notes, access scouting reports, set alerts, and share results by email. The app can be downloaded from Genuity.com/RootwormManager or iTunes® App Store.