Grasshoppers are among the insects which mostly feed on corn and alfalfa. However, if this plant is not available they also feed on other green plants. Grasshoppers eat up to the weight of its own body and can feed for about 15-16 hours a day. The best way to keep grasshoppers away is by spraying insecticides like Malathion, Nosema locustae and Carbaryl (Sevin).