Issue No. 23, Article 2.5/October 8, 2004
Follow-up to Our Article Regarding YieldGard Rootworm Corn
In issue No. 22 (September 3, 2004) of the Bulletin, we published an article titled "Transgenic Corn Rootworm Hybrid Stumbles in Urbana Experiment; Some Producers Also Report Severe Lodging with YieldGard Rootworm Hybrids in Commercial Fields." Not surprisingly, the article attracted quite a bit of attention and generated a fair amount of media coverage. Based upon some feedback we received, interpretations of the intent of article range from "Thank you for your balanced reporting" to "The University of Illinois has taken a stance against YieldGard Rootworm corn." We appreciate the former interpretation, but we are dismayed by the latter interpretation. So, we wish to clarify the intent of the article.
We did not take a stance in the September 3 article; we objectively reported facts. We are obligated to report the findings from our applied research trials to the citizens of Illinois. In fact, we report the results from our standard rootworm-control trials annually. For as long as we have reported these results, we have reported both consistent and inconsistent performance by all the rootworm-control products tested. On numerous occasions, we have reported instances of poor performance by products that otherwise had performed very well in trials conducted in previous years. However, reporting of such instances of poor performance does not lead us to eliminate the product(s) in question immediately from our recommendations for rootworm control. In 2005, we will still recommend YieldGard Rootworm corn as one of several products that can be used for management of corn rootworms.
The truth is that rootworm larval damage to YieldGard Rootworm corn in our standard rootworm-control trials was greater than we had anticipated. Before the "stumble" in our trial in Urbana (and a trial in Indiana), YieldGard Rootworm hybrids had been the most consistent product for rootworm control in trials throughout the Corn Belt. We still believe that YieldGard Rootworm corn is a viable product for management of corn rootworms. However, the instance of less-than-anticipated performance of YieldGard Rootworm corn in our Urbana trial requires investigation so that we share the cause(s) with growers.
We have learned from Monsanto personnel that the level of expression of the Cry3Bb1 protein declines as the corn plants mature, as does the level of other Bt proteins in other types of Bt corn, i.e., Herculex and YieldGard Corn Borer hybrids. Apparently, this actuality can be viewed as one possible explanation for the greater-than-expected root damage we observed in our trials. However, we remind you that this actuality is not shared broadly with customers when YieldGard Rootworm corn hybrids are being promoted for "season-long protection" against corn rootworms. If declining expression of Bt proteins compromises rootworm control, producers should be made aware of this.
We all know that none of the rootworm-control products on the market are bullet-proof. Before we reported the average root ratings from our rootworm-control trials and focused on the performance of YieldGard Rootworm corn in our Urbana trial, we wrote several articles in the Bulletin about reports of unacceptable performance of soil insecticides and insecticidal seed treatments. To refresh your memory, read the articles we published in the June and July, 2004, issues of the Bulletin. In the past, even the mighty among soil insecticides--those with excellent records of performance--have fallen, e.g., chlorinated hydrocarbons, Furadan 15G, and Amaze 20G. Instances of poor performance also have been noted for all of the currently recommended soil insecticides and insecticidal seed treatments. So, despite your perception of "season-long protection," such may not always be the case.
Throughout their history with corn, corn rootworms have been among the most difficult field crop insect pests to manage. Excellent rootworm-control products have fallen by the wayside, and current rootworm-control products will be challenged by rootworms annually. Never underestimate the ability of corn rootworms to spoil our expectations.--Kevin Steffey and Mike Gray