Interactive Node-Injury Scale

The root injury illustrated demonstrates how the Node-Injury Scale quantifies progressive feeding by corn rootworm larvae. The actual sequence of feeding will vary visually depending on a variety of conditions such as planting date, corn variety, degree days, soil moisture, insecticide application and placement, genetically modified roots, soil conditions, etc. The secondary roots (root hairs) are displayed only when no injury is represented; they have been removed to facilitate better viewing of the injury once larval feeding is simulated.

Node-Injury Scale

(Oleson, J.D., Y. Park, T.M. Nowatzki, and J.J. Tollefson. 2005. J. Econ Entomol. 98(1): 1-8)

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 1½ 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)

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.

Node injury scale
Click for Interactive Node Injury Scale

To use the interactive node-injury scale, click on the image above. The scale will appear in a new window. Once the scale has loaded, use arrow keys for precise movement: up and down to increase/decrease root injury and left and right to rotate the root.

The scale is a large file (9 MB) and requires QuickTime 4 or later.

1-6 "Traditional" Scale

(Hills, T.M. & D.C. Peters. 1971. J. Econ. Entomol. 64: 764-765)

1 No damage or only a few minor feeding scars
2 Feeding scars evident, but no roots eaten off to within 1 1/2 inches of the plant
3 Several roots eaten off to within 1 1/2 inches of the plant, but never the equivalent of an entire node of roots destroyed
4 One node of roots completely destroyed
5 Two nodes of roots completely destroyed
6 Three or more nodes of roots destroyed

This page is part of the Iowa State Entomology site. Published November 26, 2001. Last updated March 2, 2005 by John VanDyk