Beetle counts ranged from 0-7.2 per plant. Kewaunee county claimed the highest number of beetles per plant. The northwest, west central, and east central areas of the state averaged above the treatment threshold of 0.75 beetles per plant. North central fields dropped from 0.2 in 1999 to zero in 2000. We survey annually for the adult stage of this insect to determine the potential for corn rootworm pressure in fields that will be planted to corn again the following spring.
Crop rotation remains the best method for control.
Corn rootworm larvae need the corn roots for food. Growers who plant corn following corn may need a soil insecticide in the spring. Fields that had more than an average of 0.75 beetles per plant in the summer may require treatment in the upcoming spring to prevent economic damage.