Corn Rootworm Management

Managing corn rootworms (CRW) is an important function to help protect yield potential. Crop rotation, use of multiple mode of action insect protected seeds, and soil applied insecticides are management tools to consider.

Three species of corn rootworms are prominent in central and northern Illinois, western (WCRW), northern (NCRW), and southern (SCRW). However, WCRW and NCRW are generally the species most prevalent and can cause the most damage because of their life cycles. The WCRW beetle is identifiable by the black stripes on the wings. The NCRW beetle is tan to pale green in color and the SCRW beetle can be identified by its greenish-yellow body and twelve distinctive black spots.

Crop rotation should be the primary consideration for any field which has been planted to 3 or more years of continuous corn and has experienced CRW performance issues. Population studies have shown that about 25-35% of second year corn fields have a high potential to have a damaging CRW population while 50-70% of third year fields and 80-100% of fourth year and older fields have a high potential of economic CRW populations.1

The selection of a rotation crop is often dependent on the agronomics of the field. Soybean is a frequent choice; however, other rotational crops include sunflower, sorghum (grain and forage), oats, and wheat. Rotation may not provide the desired benefit where the WCRW variant feeds in soybean.

Planting corn seed with B.t. insect protection for CRW is another option. In fields with low to moderate CRW pressure, products with Genuity® VT Triple PRO® technology plus a soil applied insecticide (SAI), such as Precept™ Insecticide (Restricted Use Pesticide), or a pyramided trait product, such as those with Genuity® SmartStax® technology should be used. Pyramided products offer at least two modes of action (MOA) protection for CRW. Except in areas with known populations of the WCRW soybean variant, first year corn products can generally be planted without any CRW B.t. traits. An example would be planting a product with Genuity® VT Double PRO® technology alone, or with an SAI.

Pyramided protection or products with Genuity® VT Triple PRO® technology with an SAI should be used in areas where populations of the WCRW variant exist, in continuous corn programs, and other situations where CRW populations are expected to be moderate to high.

Products should also be selected that meet other agronomic needs for particular fields. Disease resistance, standability, drought tolerance, relative maturity, and other characteristics should also be evaluated.