Universities evaluate nodes of roots injured by corn rootworm

Research conducted by several Midwest universities confirms that hybrids with the Herculex® RW Rootworm protection trait or Herculex® XTRA gene were consistently superior to other corn rootworm management options -- transgenic or soil insecticides.

In 14 university trials, Pioneer hybrids with the Herculex® RW gene were twice as effective in protecting against root damage, on average, as hybrids with the YieldGard® Rootworm gene developed by Monsanto.

"For the past two years, where we've had moderate to heavy corn rootworm feeding, Herculex® RW has been very consistent with little to slight pruning of roots," said Jim Oleson, Iowa State University entomology research associate. "This is great news for growers. It gives them another option for corn rootworm management."

The university trials evaluated nodes of roots injured by corn rootworm. Herculex® RW averaged 0.15 nodes destroyed, whereas YieldGard® Rootworm averaged 0.32 and the untreated check averaged 1.63. At five locations with very heavy pressure from the eastern variant of western corn rootworm, the check averaged 2.5 nodes destroyed, YieldGard® Rootworm averaged 0.71 and Herculex® RW averaged 0.31.

Evaluations are based on a 0-3 root node scale with 0 being no damage and 3 a fully damaged root.

In addition, consistency ratings, an indicator of variability of root protection, were noticeably higher for Herculex® RW and Herculex® XTRA rootworm technologies compared to YieldGard® RW.

Hybrids with the Herculex® RW trait offer control of western, northern and Mexican corn rootworms. Hybrids featuring Herculex® XTRA insect protection contain both Herculex® I and Herculex® RW to guard against a broader range of above- and below-ground insects in corn than any other in-seed product on the market.

University of Illinois crop sciences professor and extension coordinator Mike Gray and his colleagues compared transgenic corn rootworm traits at three research locations.

"At two of our locations, DeKalb and Monmouth, corn rootworm feeding on hybrids with Herculex® RW and YieldGard® Rootworm was similar," said Gray. "Although under severe variant western corn rootworm pressure at Urbana, there was significant root injury to the YieldGard® RW corn plants. Hybrids with the Herculex® RW technology had significantly lower node injury ratings and performed more consistently than the YieldGard® Rootworm hybrid at the Urbana location."

Bob Wright, University of Nebraska research and extension entomologist said they planted Pioneer® hybrid 33B53 with Herculex® XTRA in their 2006 replicated trials, with overhead irrigation at Clay Center, Nebraska.

"Against high rootworm pressure -- two nodes of roots pruned in the untreated check -- Herculex® XTRA plus Poncho® 250 provided a high degree of protection from root injury by corn rootworms," noted Wright.

Corn Rootworm Continual Problem for Growers

"Corn rootworm (CRW) larvae are one of the most destructive insects of corn in North America," said Paula Davis, Pioneer entomologist. "Many growers don't realize how much they are losing to the pest every year."

Yield losses from corn rootworms of 10 percent to more than 30 percent are common with moderate to high corn rootworm populations in untreated fields. Corn rootworm feeding causes a reduction in root mass, which can affect standability and reduce water and nutrient transport in the plant, ultimately impacting grain development.

"The variant western corn rootworm continues to expand its territory, especially in Illinois, Indiana and Wisconsin," said Davis.

Wright added regarding Nebraska, "Historically growers in this state have planted corn after corn more frequently than growers in the eastern Corn Belt. Because of that, corn rootworm has been an important pest. Recent relatively mild winters also have encouraged survival of corn rootworms in many parts of Nebraska."

Iowa growers also need to scout fields, said Oleson.

"Year in and year out, corn rootworm can be an issue for Iowa growers, although pressure may vary from year to year," said Oleson. "Growers are concerned, and so are we. We encourage growers to scout fields. We've also been doing some survey work to monitor corn rootworm."

Gray agreed that scouting fields is critical so growers can go into the next growing season with a plan.

"In reality, I see too many growers not taking time to scout their fields," said Gray. "Growers should set up yellow sticky traps, and if a soybean field reaches five beetles per trap per day, that field has reached an economic threshold where a grower should consider several rootworm management options for next year."

Pioneer Hi-Bred International, Inc., a subsidiary of DuPont, is the world's leading source of customized solutions for farmers, livestock producers and grain and oilseed processors. With headquarters in Des Moines, Iowa, Pioneer provides access to advanced plant genetics, crop protection solutions and quality crop systems to customers in nearly 70 countries. DuPont is a science-based products and services company. Founded in 1802, DuPont puts science to work by creating sustainable solutions essential to a better, safer, healthier life for people everywhere. Operating in more than 70 countries, DuPont offers a wide range of innovative products and services for markets including agriculture and food; building and construction; communications; and transportation.

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Herculex insect protection technology by Dow AgroSciences and Pioneer Hi-Bred.
® Herculex and the HX logo are registered trademarks of Dow AgroSciences LLC.
® YieldGard Rootworm is a registered trademark used under license from Monsanto Company.
® Poncho is a registered trademark of Bayer AG.