We are at the time of our growing season for corn and soybeans where scouting insects is important. In corn, we are primarily worried about the corn rootworm species that are prevalent in corn fields that are under certain production parameters, chiefly continuous corn cropping. Dr. Janet Knodel, NDSU extension entomologist, published a concise article about what her team has found thus far this season here: https://www.ag.ndsu.edu/cpr/entomology/corn-rootworms-emerging-08-18-16
Scouting for root feeding and adult beetles are both timely right now, so I want to review some methods and procedures for both processes. If you are interested in scouting any fields that you might suspect to have corn rootworm feeding, review the following two YouTube videos for practical advice.
Scouting for Adult Corn Rootworm in Field Corn
https://www.youtube.com/watch?v=E4aa4DALOCc
Root Assessment for Corn Rootworm Larval Feeding Injury in Field Corn
https://www.youtube.com/watch?v=_3FvOXqOSpc
Lastly, with CRW it is critically important to plan for the future. Just as resistance has been increasing in weeds to certain herbicide modes of action, so too are corn rootworms able to develop resistance to Bt traits under the right circumstances. While there is no known resistance to Bt traits in corn rootworms in ND at the moment, we are knowledgeable today so that we can plan for the future. Therefore, when possible, rotate Bt-rootworm traits from different seed companies and genetics using this hand Bt trait table produced by Michigan State University entomologist Chris DiFonzo: https://www.ag.ndsu.edu/extensionentomology/field-crops-insect-pests/Documents/corn/28BtTraitTable2016.pdf. This is especially true for those in continuous corn production for silage or grain.
