Bt corn registrants are required to submit annual resistance monitoring reports for corn rootworm (CRW). These reports have generally addressed two objectives:

• bioassay results of CRW populations sampled from random locations in the Corn Belt; and
• the results of investigations into unexpected  CRW damage to Bt corn fields.

As of 2016, EPA no longer requires the annual monitoring of populations randomly collected from the Corn Belt. Instead, registrants are required to submit a report detailing unexpected damage investigations.  View more information on the resistance monitoring program for CRW. 

The table at the link below lists the resistance monitoring reports received by EPA. Individual studies are identified by MRID numbers.

• Corn Rootworm Resistance Monitoring Studies Submitted to EPA Bt (PDF)(4 pp, 50 K)