University of Illinois (U of I) entomologists question the value of rootworm injury ratings for predicting yields from transgenic corn hybrids in the Dec. 7, 2007 Issue of the Bulletin, a newsletter with pest management and crop development information.

In the article, “Yield Data from the University of Illinois Standard Corn Rootworm Product Efficacy Trials,” authors Kevin Steffey, Mike Gray and Ron Estes point out that root protection and transgenic corn yields don’t always correlate. For example, at the DeKalb test plot, “the mean yield of YGVT (DKC61-69) was 225.53 bu./acre and the mean yield of HxXTRA (Pioneer 33T59) was 216.18, despite comparable mean node-injury ratings of 0.2 and 0.08, respectively,” they write. “And despite a mean node-injury rating of 0.84 at Urbana, the mean yield for YGVT was 206.17, significantly larger than the mean yield of HxXTRA (Pioneer; 153.79 bu./acre) with a mean node injury rating of 0.49.”

In other words, the Dekalb hybrid with YieldGard rootworm protection recorded a better yield (9 bu./acre more at DeKalb and more than 50 bu./acre better at Urbana) than the Pioneer hybrid with Herculex XTRA rootworm protection, even though it sustained more root injury. This result and others like it “raise significant questions about the utility of root ratings as the sole determinant of rootworm larval injury and their relationship to yield,” conclude the U of I entomologists. “Both the 1-to-6 root rating scale (Hills and Peters 1971) and the more recent node-injury scale (Oleson et al. 2005) were developed while soil insecticides were the primary tools being used for control of corn rootworms. Now that we have entered a new era of rootworm management, a new standard seems to be justified.”

To find out more about yields and products tested for corn rootworm control during the 2007 U of I corn rootworm trials, click here:

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