Tillage won’t solve corn rootworm, corn borer woes

Corn Pest Beat: You need a season-long approach to control these pests. 
Sep 29, 2021
We found corn borer damage in some fields this year, and our crop scout found some corn rootworm injury, too. Will tillage help for these insects? How should we manage for them for 2022?
The Indiana certified crop adviser panel answering this question includes Traci Bultemeier, an agronomist with Pioneer near Fort Wayne; Jesse Grogan, a retired agronomist based in Lafayette; and Bryan Overstreet, an Extension ag educator for Purdue University Extension in Jasper County.
Bultemeier: Tillage is not going to have any significant effect on these insect populations. The optimal management suggestions for both insects are crop rotation and use of trait technology in the corn hybrids.
Grogan: Tillage does not help with these insect pests. Corn rootworm eggs can survive soil movement, and larva hatch occurs in June, after the crop is planted. Corn borer larvae survive above ground in residue, but not all residue is buried each year. Female corn borers emerging from neighboring fields can fly over distances and lay hundreds of eggs on calm nights in the summer.
Corn rootworm pressure can be predicted for the following year. A proven method is to place Pheracon AM sticky traps in corn or soybean fields to monitor adult activity from about mid-July into early August in the previous year. Find instructions for doing this in Purdue University Publication E-218-W. Also, it is possible to get information about corn rootworm risk from a seed representative who has access to regional monitoring data. Corn borers will always be present because they have a wider host range and survive in crop residue.
Effective control of these pests is achieved with transgenic corn hybrids with genes for control of European corn borer and corn rootworm. Multiple genes are stacked together for control of both pests that also include insect refuge seed in the bag or box. Insect control in non-GMO corn is achieved with insecticides as was used in the 1990s. You can control corn rootworm with soil-applied insecticides and corn borer with foliar insecticides.
Corn borer activity for non-GMO corn can be monitored with black-light trap catches or field scouting of first-generation larvae in the early to mid-whorl growth stages. For the second generation, look for egg masses under leaves at ear level during the pollination period. A guide for field scouting and control decisions is found in Purdue University Publication E-17-W.
Overstreet: Clean tillage with a moldboard plow may reduce the overwinter population of corn borer, but research shows it really does not reduce next year’s damage. For that reason, it is not a recommended practice. For the corn borer, you could look into Bt hybrids, or just wait until next season and scout for the moths and egg masses and treat accordingly at the time with an insecticide if needed.
For the corn rootworm, most planters are not set up for insecticide application today. If you have this option, this would be a good option to use. If this is not an option, I would consider using a Bt hybrid that is bred for rootworm control.