BACKGROUND

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is one of the most serious pests of corn (Zea mays L.) In 2017 and 2018, studies were conducted in fields with and without known unexpected root injury to Cry3Bb1, to determine root protection by Bt corn hybrids expressing both mCry3A and eCry3.1Ab insecticidal crystal proteins, and hybrids expressing either mCry3A or eCry3.1Ab only against the WCR root injury. Node injury was evaluated using the Iowa State University 0-3 node-injury scale (NIS), and the consistency of root protection was also determined.

RESULTS

In 2017, with medium to high larval feeding pressure, the Bt corn hybrids expressing both mCry3A and eCry3.1Ab in the breeding stack, molecular stack, and Bt corn hybrid expressing eCry3.1Ab only, sustained low node injury compared with Bt corn hybrid expressing mCry3A only, and the non-Bt corn. In 2018, with low larval feeding pressure in most of the locations, node injury was not different for the Bt and Non-Bt corn hybrids. Across all locations in both years, the Bt corn hybrids expressing both mCry3A and eCry3.1Ab provided better and consistent node injury protection.

CONCLUSION

Bt corn hybrids expressing both mCry3A and eCry3.1Ab proteins provided better root protection and consistency than the Bt corn hybrid expressing mCry3A only, and non-Bt. Therefore, stacking of Bt traits will be the best option for managing insect resistance. © 2023 Society of Chemical Industry.