Ag is My Bag: Roundup, rootworms, and Charles Darwin

Posted: Aug. 11, 2011 1:30 pm Updated: Nov. 29, 2014 8:17 am


Having too much of a good thing is not a good thing. In some homes chocolate cake is a good thing, but having too much of it puts on pounds and pimples.

And that has been the way for farmers in recent years. Having too much of a good thing has come back to bite their tail lights.

The all knew that overuse of Roundup would create problems in bean fields, and now many of them are suffering. The news this week about corn rootworms can be put in the same category, and they know exactly what that means.

Agricultural technology has kept U.S. farmers competitive and profitable. The money that Monsanto, Pioneer, Syngenta, and other life sciences companies pump into research has solved a myriad of daily farm problems. Monsanto's Roundup genetics inserted into soybeans, put weed-hook manufacturers out of business. Fields were clean, labor was less, and time was saved.

When the same gene that makes the plant resistant to the glyphosate chemical in Roundup was also inserted into corn, cotton, and other crops, then glyphosate could be used on all of them to keep fields weed free at a reasonable cost. But using only one herbicide lead to weeds developing resistance, and now tens of thousands of Corn Belt farmers have a patch of weeds that Roundup will not kill. The weeds have adapted and are survivors. We have used too much of a good thing, and without rotating Roundup with other herbicides, there are weeds now that cannot be killed unless they meet a weed hook or a cultivator shovel.

Although most farmers learned the lesson the hard way and have a weed problem, the majority apparently did not really learn the lesson very well, or at least did not apply it to another problem, corn rootworms.

Agricultural technology provided the Bt gene that is inserted into corn and the first corn rootworm to nibble at a tender corn root got a gut full of a toxic protein that was deadly. In a few short years a majority of the corn planted in the U.S. had the Bt gene and it was killing rootworm larvae left and right. Almost all of them.

To ensure that the Bt genetics did not go the way of Roundup, entomologists and seed companies urged farmers to plant 20 percent of their acreage with a non-Bt corn and use a conventional insecticide on it. The latest survey results indicate 80 percent of farmers really liked the yield response from the Bt corn and planted their entire acreage with those hybrids.

And since corn is more profitable than soybeans, many fields are continuously planted in corn, supposedly killing those corn rootworm larvae year after year. Supposedly.

Entomologists at Iowa State University reported last week they have found corn rootworms in northeastern Iowa which are resistant to Bt toxins in the corn that is planted in nearly every field. Extension entomologist Mike Gray at the University of Illinois said that was no surprise because farmers were not planting the non-Bt hybrids as prescribed. His colleagues at Purdue said exactly the same thing and added, "The genie cannot be put back in the bottle."

Both Roundup and Bt genetics have increased agricultural profitability, but being a good thing, we have used too much of it. Based on their headaches with glyphosate resistant weeds, many farmers may change their corn planting practices in 2012, and follow the rules for controlling corn rootworms, if it is not already too late. But chances are, mutants already have been created in thousands of Corn Belt fields, and they are adapting and surviving.

Farmers can't blame Charles Darwin, only themselves.


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