Secondary Insect Pests in Corn: The Watch Begins

March 17, 2000
The mild winter, the unusually warm weather in late February and early March, and the lack of excess moisture (an obvious understatement) have growers thinking about planting corn. We have heard that some corn has been planted already, and corn planting will probably get under way with a vengeance very soon. Consequently, we entomologists are going to pay particular attention this year to a host of so-called secondary insect pests of corn.

Billbug adult on corn seedling.

Black cutworm larva.

Grape colaspis larvae in the soil.

Brown stink bug adult.

White grub larva.

Handful of wireworms.

During the winter months, I spoke frequently about cutworms, grape colaspis, white grubs, and wireworms, and a few times I threw in some information about billbugs, southern corn leaf beetles, and stink bugs. It had been quite some time since we had addressed these problems, and you folks had been telling us it was high time to get back to it. During the last couple of years, incidents of damage to corn caused by one or more of these pests have increased, causing considerable concern among some corn growers.

I have speculated that the trend toward earlier planting might be responsible, at least in part, for the greater frequency of problems caused by some of the secondary insect pests of corn. The longer the seed and seedlings are exposed to attack by these "cool-season" insects, the more likely economic damage will occur. In addition, corn grows rather slowly in cool soil, and slow-growing corn is almost always more susceptible to subterranean insect problems than fast-growing corn that can "grow past" the feeding injury. If my speculation is correct and if corn is planted early in 2000, we should anticipate some early-season insect problems.

What I learned during preparation for my discussions this winter was that we don't have a whole lot of new research information about secondary insect pests of corn. Even insecticide efficacy data are limited. As a consequence, we find ourselves relying on decades-old literature for some of these insects. However, much has changed in agriculture in the Corn Belt since publication of that information from the early 1900s through the 1950s. It's probably time to gather some new data.

John Shaw (coordinator of our Insect Management and Insecticide Evaluation Program), Mike Gray, and I will be conducting several insecticide-efficacy trials for control of secondary insects this spring. We will look at the efficacy of soil insecticides, seed treatments, and maybe a transgenic hybrid here and there to determine what works for these difficult-to-forecast insect pests. In addition, I am hoping to make more field visits this year than I have in recent years. If you encounter any significant problems caused by secondary insect pests in corn, get in touch with me. I won't promise that I will rush out to every field exhibiting such a problem, but I want to see firsthand what some of these critters are doing. So stay in touch.--Kevin Steffey

Author: Kevin Steffey