The Iowa State Nodal Injury Scale
Rating Corn Rootworm Damage
Root damage is rated on a scale of 0 to 3 (see table below). Damage in between complete nodes eaten is noted as the percentage of the node missing, i.e. 1.50 = 1 1/2 nodes eaten, 0.25 = 1/4 of one node eaten, etc.
| Value | Description |
| 0.00 | No feeding damage (lowest rating that can be given) |
| 1.00 | One node (circle of roots), or the equivalent of an entire node, eaten back to within approximately 1.5 inches of the stalk (soil line on the 7th node) |
| 2.00 | Two complete nodes eaten |
| 3.00 | Three or more nodes eaten (highest rating that can be given) |
Click on the image below to view an interactive version of the scale available from Iowa State University's Department of Entomology. You will be able to drag the red marker to different injury levels and watch the roots change.
