Older fields should be scouted first. The larvae are most commonly found in the midrib and leaf axil. At each location pull open the whorl to check for larvae feeding within the whorl. If the majority of larvae have bored into the stalk, do not apply insecticides as they are ineffective once the larvae have entered the stalk. If no larvae or egg masses are found, repeat scouting every five to seven days.
Bt corn is a type of corn that has been genetically modified.
Bt stands for Bacillus thuringiensis , a bacterium that has insecticidal properties when ingested by certain types of insects. Bt is a naturally occurring soilborne bacterium that produces crystal-like proteins that selectively kill certain groups of insects. The protein crystals are insect stomach poisons that are activated by the insects digestive enzymes to form the toxin. Since the Bt is right in the corn plant, the only way insects are exposed to it, is eating the corn plant. Bt corn does not control feeding by most insects other than the European corn borer.