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Rootworm, Palmer amaranth discussed at U of I field day



Illinois Correspondent


SHABBONA, Ill. — This year has been a quiet one in terms of insect management, Mike Gray told visitors to the University of Illinois research farm near Shabbona, Ill.

As it does every year, the staff at the 160-acre Northern Illinois Agronomy Research Center hosted the field day to discuss insects and diseases that affect corn and soybeans across the state of Illinois. More than 45 individual research projects encompassing corn, soybeans, oats and cover crops are under way.

Studies include evaluating crop rotations, date of planting, row spacing, plant populations, crop diseases, variety comparisons and crop nutrient management. Gray, entomology professor and extension specialist, said even though corn rootworm has not been a big issue this year, the ongoing concern is resistance to Bt corn. Available commercially since 2003, Bt corn has provided 5 percent greater yields with an overall impact of $10 to $50 per acre – or $7.1 billion overall, Gray said.

Some resistance has been found in Illinois in the counties of Livingston, Kankakee, Whiteside, Henry, Sangamon, Mercer and McDonough, Gray said. The greatest potential for infestation and eventual resistance is in fields planted in corn year after year, he added.

With only four Bt proteins available on the market today, Gray said, "There aren’t a lot of tools let in the arsenal" to combat Western corn rootworm. He said a new transgenic technology is in the research pipeline, but each firm working on it gives the same answer for its potential availability – end of the decade.

Gray’s recommendations for reducing rootworm include implementing a more diverse crop rotation, use of a non-Bt hybrid, planting pyramided hybrids that contain more than one Bt protein and possible use of an adult suppression program. The good news for soybean growers, according to Gray, is that soybean aphids are a no-show this year.

"They could come on late, but I doubt it," Gray said. "With the brutal winter we had, they didn’t overwinter well."

On the next stop of the field tour, Doug Maxwell, principal research specialist in the department of crop sciences, talked about herbicide resistance, specifically for Palmer amaranth.

"Palmer is showing up everywhere," Maxwell said. "And we’re not even sure how the seed travels." He speculated it could be traveling with cover crop seed.

"Look for something that looks like it doesn’t belong," Maxwell said. "And if you’re seeing it, just keep in mind where you got the cover crop seed."

He said Palmer amaranth is a very competitive weed and grows faster than waterhemp. Maxwell said it’s crucial to catch the plant when it’s small. "Once that plant gets its root system in place, by about 4 to 6 inches in height, it’s difficult to control. And it doesn’t matter what chemistry you use."

At this point, Maxwell said he doesn’t have any long-term answers, although crop rotation would be helpful – "anything to break up the cycle."

Additional discussions included nitrogen fertilization for soybeans by Emerson Nafziger, professor and extension specialist in crop production; fungicide resistance by Carl Bradley, associate professor and extension specialist in plant pathology; advances in nozzle technology by Matt Gill, field research assistant; and soybean planting date effects on yield by Jake Vossenkemper, graduate research assistant in crop sciences.

Used for crop research since 1948, the farm is the northernmost research center in the University of Illinois crop sciences department that is dedicated primarily to row crop research. Visitors are always welcome. For more information, contact farm manager Russ Higgins, extension educator in crop sciences, at 815-274-1343 or email