A moisture utilization study conducted by Monsanto this season has provided a unique look at how YieldGard® Plus Corn roots are able to effectively absorb subsoil moisture under dry conditions.

The study involved placement of 60 moisture probes at five different locations across the Corn Belt to compare the root performance of YieldGard Plus plants with YieldGard Corn Borer hybrids protected by soil-applied insecticides. The probes, extending five feet underground, were in place from mid-June through September, providing data every 15 minutes on relative water density at different soil depths. Based on these readings during the growing season, root depth and water absorption could be monitored.

Stress Mitigation trials like this one in Iowa clearly show the moisture utilization benefits delivered by YieldGard® Plus technologies. In the clear-tent covered plots to allow sunlight but not moisture, YieldGard Plus hybrids (on the left) exhibited greater above ground stalk height and longer, healthier roots below ground versus non-YieldGard Rootworm protected hybrids (on the right). (Photo: Amana, Iowa, August 2006)

According to Clint Pilcher, Monsanto Corn Technology Development Manager, test results demonstrated that YieldGard Plus hybrids, with in-plant rootworm control, developed longer, healthier roots than soil insecticide-protected corn, which in turn resulted in significantly better moisture uptake.

"Before, we had to rely on root digs to observe root growth and rootworm feeding patterns," Pilcher said. "These moisture probes help us understand what the roots are experiencing below ground. YieldGard Plus protects the roots, allowing them to go deeper into the soil profile, which improves water use efficiency compared to conventional hybrids treated with a soil insecticide.”

Improved water utilization, Pilcher added, has contributed to the average 14.6 bushel-per-acre yield advantage that YieldGard Rootworm and YieldGard Plus corn hybrids achieved across the Corn Belt this season compared to soil insecticide-protected hybrids based on over 500 comparisons in 2006.

Stress Mitigation Trials Continue to Uncover Trait Benefits

Data is still being compiled from the moisture probes (provided by AgriLink Company Ltd.), Pilcher said, but initial results are consistent with those of a similar study conducted the last two years at the University of Nebraska. Those studies, also involving moisture probes, have shown that the fuller root mass of YieldGard Plus corn hybrids was able to utilize about 3.0 more inches of subsoil moisture than corn protected with soil insecticides.

The Monsanto probes were part of a "stress mitigation" study during the 2006 season, demonstrating how YieldGard Plus is able to help reduce the stress of dry weather on corn plants. Most of the moisture probes were placed in Monsanto stress mitigation plots, which were grown under 40-foot by 50-foot tents with a clear vinyl top that allowed the corn plants to receive sunlight but not rain. Under these simulated dry conditions, YieldGard Plus corn hybrids achieved a 31.2 bushel-per-acre yield advantage over soil-insecticide protected corn.

"Bottle Brush" Roots Observed with Herculex® XTRA Hybrids

Another study conducted by Monsanto this season revealed an interesting difference in the way that the YieldGard Plus and Herculex® XTRA rootworm hybrids control rootworms. The program involved 80 test plots across the corn belt, involving head-to-head comparisons of YieldGard Rootworm or YieldGard Plus corn against Herculex RW or Herculex XTRA.

“From our summer root digs, we observed that both YieldGard and Herculex technologies are very good as far as controlling rootworm,” Pilcher said. “However, there are differences in the way the rootworm larvae feed on the roots from the different technologies, and subsequently, there are differences in how those roots respond to that feeding.”

Pilcher said with most of the Herculex hybrids evaluated, "we observed a root response to larval feeding that seemed to trigger regenerative root growth, which we refer to as a ‘bottle brushing’ root response.”

These observations were confirmed in a recent newsletter (The Bulletin, No. 24, Nov. 3, 2006) published by the University of Illinois where Mike Gray and Kevin Steffey observed a “very unusual root morphology of our Herculex XTRA Rootworm hybrids...” They went on to state that "the injured roots had a characteristic 'bottlebrush' appearance.”

Pilcher explained that the Herculex plants, after getting “nicked” by early-season larval feeding, appeared to divert energy into regenerating short, stubby “bottlebrush” roots around the plant’s upper nodes. In contrast, due to early season root protection, the YieldGard Rootworm plants developed longer, more uniform roots that went deeper into the soil to absorb more moisture and nutrients. Pilcher noted that YieldGard Rootworm technology can experience larval feeding under heavy pressure, but the feeding primarily occurs later in the growing season, after most of the yield potential has already been determined.

Based on 2006 harvest data, YieldGard hybrids achieved an average 11.7 bushel per acre yield advantage over Pioneer Herculex hybrids across the Corn Belt. Pilcher said it is difficult to determine how much of the yield difference can be attributed to genetics versus rootworm feeding patterns, but that the YieldGard Plus system (germplasm plus traits) outperformed the Herculex XTRA system about 76 percent of the time. All of the Herculex XTRA plots involved Pioneer® hybrids.

“These observed yield differences seem to be even greater in regions that experienced dry growing conditions in 2006,” Pilcher said. For example, in areas of Illinois that experienced normal rainfall this season, YieldGard hybrids experienced an overall yield advantage of 18.4 bushels-per-acre over Herculex hybrids, but an even greater advantage – 26.5 bushels-per-acre – in dry areas of the state. In Iowa, YieldGard hybrids achieved a 5.6 bushel-per-acre advantage over Herculex hybrids in normal rainfall areas and a 10.4 bushel-per-acre advantage in dry areas.

“It comes back to the same thing we saw in dry areas of the Corn Belt in 2005 – the bigger YieldGard root systems being able to go down and get more moisture early, which is when the yields are determined,” said Dave Rhylander, Director of Traits for Monsanto.

Monsanto's YieldGard Rootworm Corn technology was introduced in 2003 and YieldGard Plus was launched in 2004. YieldGard Plus contains both rootworm and corn borer technologies providing farmers with above and below ground insect protection. In 2006, Monsanto's YieldGard Rootworm and YieldGard Plus technologies were used by more than 60,000 U.S. corn farmers to protect yield on more than 10 million acres.

Monsanto Company is a leading global provider of technology-based solutions and agricultural products that improve farm productivity and food quality. For more information on Monsanto, see: www.monsanto.com.

Always read and follow grain marketing and insect resistance management requirements. Follow pesticide label directions. DEKALB® is a registered trademark of DeKalb Genetics Corporation. YieldGard® is a registered trademark of Monsanto Technology LLC. All other trademarks are the property of their respective owners. ©2006 Monsanto Company.