Answers are from the Indiana certified crop adviser panel: Dan Ritter, Dairyland Seed agronomist, Rensselaer; Bryan Overstreet, soil conservation coordinator, Rensselaer; Steve Gauck, Beck’s Hybrids, Greensburg; and Dan Quinn, Purdue Extension corn specialist.

 

My wife drives the combine, and she is reporting more bowed stalks than usual in fields harvested so far. How do I know if this is from rootworm or something else — maybe just storm damage? We are in corn/soybean rotation and aren’t using rootworm insecticides or genetically modified organism (GMO) traits for rootworm. Should we reconsider our strategy for next year? 

 

Ritter: A good shovel is the best way to know. Dig up some roots and examine them for corn rootworm feeding, root structure abnormalities or root development issues. Some hybrids tend to have weaker root systems and are more prone to leaning. In other instances, soil conditions restrict root growth and development, making it more susceptible to root lodging. Once you determine the cause, work on altering your management system.

 

Depending on where you are in Indiana, you may or may not have issues with Western corn rootworm. If you are in an area with that variant and roots indicate feeding, give serious consideration to corn with corn rootworm protection.

 

Overstreet: At this time, it is very hard to tell if the root has been damaged by insects since they have naturally started to die back. Twenty years ago, I would have said that your lodging could have had a high chance of being from rootworm damage. But in the past few years, rootworm numbers have been much lower. We are starting to see a few pockets again, but generally not in first-year corn. If you are concerned, do some trials next season with a GMO product or an insecticide in the furrow or on the seed. 

 

Gauck: Don’t reconsider a strategy until you dig roots and examine fields, even if this is after harvest. As your wife is combining, ask her to look for patterns. Is the corn all leaning the same way, or is it bowed in many directions? Is it worse in areas that are open to wind or where wind can funnel into the field? Did you have a large wind event in the area, or is your field the only one affected? 

 

The main answer will come by digging roots. Look for root feeding, especially on nodal roots. Are nodal roots pruned back? Sometimes, looking at stalks can be deceiving. Be sure to reach out to an agronomist to help walk you through the process to get the right diagnosis. 

 

Quinn: The first and most important thing is to accurately determine what is causing the issue. This will involve scouting and sampling the field to determine what caused bowed stalks. In some cases, corn rootworm injury combined with storms can exacerbate root lodging/goose necking.

 

Strategies such as root digging/washing once the first adult corn rootworm beetles are observed and root injury is fresh will help give the best assessment and diagnosis of corn rootworm damage. It also will be important to walk and scout fields after storms to assess if any root lodging has occurred. If root lodging occurs early and plants upright themselves, yield losses often are minimum. However, taking necessary steps to determine the specific cause of the symptoms is very important and will help dictate if any management changes need to be implemented.