In the Rocky Mountain states, the most important pest insects can damage crop plants in a variety of ways. Insects chew leaves and needles . This type of injury may weaken the plant and cause it to be less productive. Some pests, such as many grasshoppers, will chew a wide variety of plants. Insects that chew young plants, such as cutworms and flea beetles, may kill the plant.
Insects suck the sap from plants .
Insects, such as aphids, leafhoppers and scale insects, feed on the sap from plants. In the process, they may damage plant cells or remove valuable nutrients. When young leaves are damaged, they may curl and distort. For example, this is what the Russian wheat aphid does to wheat and barley, costing growers tens of millions of dollars annually in crop losses and extra-control costs. Insects may produce galls on plants .