Corn rootworms active in northern Illinois fields

ROCHELLE, Ill. — The pruning of roots by corn rootworms can have a significant impact on yields.

“We are seeing a lot of pressure from corn rootworms and we’re seeing year-over-year increases,” said Nathan Hein, technology development representative for Bayer Crop Science. “So, the right crop rotation and the right technology in the field make a huge difference.”

Bayer representatives monitor fields constantly for pests and diseases.

“We monitor hundreds of fields for adult corn rootworm beetles and we have maps that show where the pressure was and where we expect it to go this year,” Hein said.

“This year we’re expecting a lot of activity in northern Illinois, Iowa and into Indiana,” he said from the Bayer research site near Rochelle.

Hein also evaluates corn plants at research sites near Roanoke and German Valley.

“My area covers Woodford County and north,” he said. “I do a lot of work with seed traits.”

A wide variety of trials test numerous technologies at the 75-acre site.

“We test everything from herbicide tolerance, next-generation corn rootworm, planting dates, short corn and densities,” Hein said. “Anything we can do to help the farmers have a better understanding of what to plant and when to plant it.”

One experiment is monitoring for European corn borer resistance to Cry proteins.

“A resistant population has been found in Canada,” Hein said. “So, we have sites all over the north monitoring for that movement.”

Hybrids with Bayer’s VT4PRO trait, the representative said, are good for fields with moderate to low corn rootworm pressure.

“It combines the RNAi technology from SmartStax PRO with the above-ground resistance of a Trecepta,” Hein said.

“This SmartStax PRO corn has the brace roots continuing all the way down and you can see all the root hairs that should be here,” he said during a root dig demonstration. “This would be a 0.1 on the 1 to 3 scale, which means minimal scarring.”

Hein compared that to a untraited Roundup Ready hybrid.

“It looks horrible and there is little root regrowth,” he said. “It’s a 2.5 score and it is awful compared to the SmartStax PRO.”

This root damage will have a significant impact on yield, Hein said.

“It is really devastating because it comes right at the reproductive period,” he said. “Right now, the plant is trying to transition from growing to putting its resources into grain, so it is trying take up as much as it can to keep itself going while pushing carbon into the corn.”

With a poor root system prior to reproductive stage, the corn plant has not been able to get enough nutrients and sometimes even water.

“This can reduce the amount of carbon that the cornstalk has stored for itself,” Hein said.

“If we’re seeing this much damage to the roots before the reproductive period, the corn has been using a larger percentage of nutrients to maintain growth,” the representative said.

“Moving forward, while we’ll see some regrowth in these roots, it will affect the kernel weight,” he said. “Because the plant won’t be able to take in as much carbon for the corn cob, so we’ll see a reduced yield of 10% to 30%.”

SmartStax PRO hybrids, Hein said, are recommended for acres that have the highest corn rootworm pressure.

“SmartStax hybrids are a good option for fields with moderate pressure,” the Bayer representative said.

“If you don’t have corn rootworm feeding in your fields, but you see neighbors that have the pests, you don’t necessarily have to jump straight to SmartStax hybrids,” he said.

“Starting with an insecticide can be a good option, but once you start to see corn rootworm pressure in your field, you need to start looking at traits and we always recommend rotation, as well.”

Both northern and western corn rootworms are present in the Bayer research location.

“I’ve seen more northern in our plots than western,” Hein said.

The control of these pests is becoming more complicated because some variants of the corn rootworms are changing their life cycles.

“Some of the northern rootworms have created an extended diapause life cycle, so they are able to stay underground for an extra year,” Hein said. “That combats our soybean-corn rotation, so then we recommend at least two years of growing soybeans.”

In addition, some variants of the western rootworm have learned to put eggs in soybean fields, the representative said, with the expectation that the field will have corn the next year.

“We are continuously focused on bringing new products and technology to market and right now we are working on our next generation corn rootworm technology,” Hein said.

“It will be a brand new Cry protein that the corn rootworm has never experienced and it is looking really good,” he said. “I’m really excited about it and it will probably be introduced in the next five to seven years.”