Witnessing the Effects of Increased Rootworm Pressure Firsthand

Witnessing the Effects of Increased Rootworm Pressure Firsthand

To understand the differences in ear size and kernel fill, we dug up the roots. The effects of rootworm feeding were quite evident.

Last week, I hopped in the passenger seat of Dave Shenaut's Gator for a root dig demonstration at his plots on Parkland Community College's research farm.

After checking out a number of research plots, Shenaut, a Monsanto technology development rep, took me to the main event. This spring, he planted the same hybrid with varying levels of trait protection in the middle of what was a pumpkin patch last year.

For those who don't know, pumpkins are a terrific trap crop for adult corn rootworms. Researchers rely on this crop to elevate rootworm pressure for the following year's corn experiments. This wasn't quite enough for Shenaut. He added another 50 mL of a rootworm egg slurry to some of the plots just after emergence.

Shenaut planted rows of a Genuity Smartstax hybrid side by side with rows of the same genetic hybrid, but with only the Roundup-Ready trait (no insect protection whatsoever). He used a traditional 30-inch planter, with a final stand of 35,000 plants per acre.

Approaching the plot, the difference is immediately noticeable. Much of the Roundup-only corn is lying on the ground. What was still standing was noticeably lighter (more yellow) in color.

Shenaut then began digging up plants. The roots tell the whole story. After giving them a quick wash, he rated the Smartstax a 0.1 on the root node injury scale. He put the Roundup-only hybrid at about a 2.

The fact that much of the Roundup-only corn was lying on the ground was a pretty good indicator as to the difference in the two plants. However, we wanted further verification. The ears were the icing on the cake. The Smartstax ear was full, with kernels filled to the tip. Conversely, the Roundup-only ear was much smaller with kernel fill stopping a good third from the tip.

Shenaut says the roots and corresponding ears are a good reminder of how important a hybrid's below ground insect protection is.

TAGS: Weeds
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