Count the beetles on the entire plant including the ear tip, tassel and leaf axils. When coming to the plant first grasp the ear tip to trap any beetles inside the ear. Then check the rest of the plant with the other hand. After examining the whole plant then carefully open your hand and pull back the husk to check inside the ear for any more. Control Control for the corn rootworm is difficult.
Crop rotation is the best method for control.
When the eggs hatch in the spring the worms need food, if none is present they will die. This will not kill all the worms and signs of an extended diapause have been documented. With an extension the eggs can remain in the soil for more then one year. This becomes a problem to farmer since a corn soybean rotation is desired. Chemical control can also be used at planting and cultivation.