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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.
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.
Figure 1. Expected Yield Over the Long-Term
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.
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.
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.
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).
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.
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.
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®.