Three-year test plot wraps up in the eastern Corn Belt to find a consistent response for nematode control
In a drought year such as 2012, it’s the little things that add up to more yield. Such was the case in the third and final year of a test plot looking at the control of corn nematodes with seed treatments in the Eastern Corn Belt.
"For the previous two years, we saw big visual differences in the root systems between the seed treatment and the check," says Farm Journal Associate Field Agronomist Missy Bauer, who led the effort in southern Michigan and northeast Indiana. "Then in our third year, we saw how important protecting those roots from nematode feeding could be toward increasing yield."
Nematodes, which have several species, are microscopic round worms that feed on corn roots. Pressures are on the rise for multiple reasons, some of which are more corn-on-corn rotations, reduction in the use of soil insecticides due to transgenic corn, changes in the types of soil insecticides (less organophosphates and carbamates) and reduced tillage.
Bauer planted test plots using Avicta on NK seed and Votivo on AgriGold seed. The check in the Avicta plot was treated with Cruiser insecticide, and the check in the Votivo plot was treated with Poncho insecticide. Each test plot was a split planter trial to include multiple replications across management zones.
"We began this study because we know that nematode pressures are increasing and seed treatments might be a new tool to manage them," Bauer says. "To better understand the control provided by the nematode products, we visually evaluated plant and root growth response and nematode levels in the soil and took yield into consideration. Normalized Difference Vegetation Index (NDVI) maps and yield maps from previous years were used to identify potential hot spot areas followed up by nematode testing. All of the fields had known nematode pressures with spots of moderate to high pressure.
Ground-truth hot spots. Bauer says it’s important to test the roots and the soil for nematodes during the growing season. Because nematode pressures aren’t consistent across a field, mapping the hot spots was key to evaluating the control provided by the seed treatment. The areas with high nematode pressures often occur in a circular pattern that shows up on NDVI and yield maps, which can then be ground-truthed.
"The visual difference between the treated and non-treated plants was obvious aboveground in the hot spots areas with the heaviest pressures," Bauer says. "However, it was not a 100% cure; the plants still showed signs of nematode pressure. In low pressures areas no major difference was observed in plant growth.
In the field planted with Syngenta’s Avicta treated seed the primary nematodes present included dagger, lesion, stunt and spiral. In the field planted with AgriGold’s Votivo treated seed needle, lesion, stunt and spiral nematodes were present.
Bauer reminds farmers that the seed treatment only applies to the seed—not the soil.
"We weren’t treating the soil, so we didn’t see a decrease in nematode populations," she says.
This 2011 yield data is overlaid with management zones showing yield response to the seed treatment. The highest yield response came from a management zone tested to have moderate pressure. The types of nematodes found in each area is also provided.
"We pulled several replicated samples in the plots with the seed treatment for nematode protection compared to the non-treated and saw no difference in the types or quantity of nematodes present.
The key to protecting yield from nematodes is protecting the seed and crown roots.
"The first, second and third set of crown roots are very important," Bauer says. "For example, in 2012, when we had the seed treatments it was a more consistent response in yield than previous years. This tells me that protecting every root added up in the drought."
In one field, the average response was an increase of 6.6 bu in 2012. However, by management zone the yield impact ranged from -8 bu. to 20 bu. Another field averaged 4.2 bu. and ranged from -1 bu. to 8.9 bu. The third field averaged 11.8 bu. and ranged from 3.3 bu. to 16.1 bu.
The seed treatment provided visible response in the first, second and third crown roots, with more root mass and root hairs.
In a three-year analysis, Bauer reports that the seed treatments increased yields by an average of 3.5 bu. in 2010, 3.4 bu. in 2011 and 7.5 bu. in 2012.
"Our plot data is analyzed by management zone, and we factor in those hot spots with high pressures," she says. "Over three years we confirmed higher responses to the seed treatment where we had moderate to high pressures."
Bauer believes the key tool that the seed treatments provide is protecting the roots that lead to higher yields. "That’s where the yield advantage is coming from, having healthier roots is making the difference," she says.
Each Farm Journal Test Plot is a cooperative effort. Our thanks go to: Syngenta and Palle Pedersen; AgriGold Hybrids, Mike Kavanaugh, John Kermicle, Phil McCutchan and Justin Warren; Bayer CropScience and Dennis Clark; GeoVantage and Nick Morrow; Terry Finegan; Willibey Bros.; B&M Crop Consulting.
You can e-mail Margy Fischer at email@example.com.