Corn Stalk Response to Plant Population and the Bt–European Corn Borer Trait

Current research indicates that plant populations should increase above the current Wisconsin recommendation of 74 100 plants ha21 for higher corn (Zea mays L.) grain yields. However, stalk lodging is a major constraint to increasing plant populations. One option growers have is using Bt (Bacillus thuringiensis) hybrids, which are known to lodge less. A new method for assessing stalk lodging risk is needed. The objectives of this study were to (i) assess rind strength of corn hybrids with or without the Bt trait to increasing plant populations at natural levels of European Corn Borer [ECB, Ostrinia nubilalis (Hübner)], and (ii) determine the potential of rind strength measure-ments for predicting stalk lodging. In 2003 and 2004, rind penetrom-eter resistance (RPR) was used to measure rind strength for four Bt and five non-Bt hybrids with plant populations ranging from 64 220 to 123 500 plants ha21 at 10 locations in Wisconsin. Stalk lodgin