If these weeds are killed with herbicides, the stalk borers will move out of the weeds and into the corn. Stalk borers can destroy a corn stand under these circumstances. Be sure to read the insecticide label before mixing pesticides. Stalk borer damage to corn border rows. If the number of infested plants exceeds the percentage given for the plant stage, then an insecticide application can be economically justified.
Young plants have a lower threshold because they are more easily killed than older plants.
Scouting can stop when the plants reach the V7 stage. Thanks to Larry Pedigo, entomologist at Iowa State University, for development of the economic thresholds. These products, with the exception of Lorsban, are restricted use pesticides. Always read and follow label directions. This information subject to a usage policy .