The Yuma IPM TEAM received some wheat samples from Jim Ellsworth, a PCA in Yuma, AZ. The plants showed an injury or a discoloration evenly spaced on the leaves. In some cases double spots on the opposite side of the leaves but always the spacing was pretty even (about 0.5" apart). The previous crop was lettuce and melons with different herbicide regimens. There was no defined herbicide drift pattern observed in the field. The affected area was approximately 100 ac located in Wellton, AZ. The team determined it was due to abiotic factors discarding insect damage, disease symptoms. You can check out the symptoms in the following video from January 11, 2012: "Wheat in Wellton AZ".

Diagnosis:

"We know it is not herbicide injury, it is related to stress and damage as the leaf is unfolding. It could be cold weather at emergence." -Barry Tickes, University of AZ Cooperative Extension.

"Physical damage or some sort of environmental stress as the seedling is emerging. Plants that have trouble emerging through a crust, and the leaves are folding under the crust. The chlorotic strips appear at the folds of the leaves". -Mike Ottman, Extension Agronomist, University of Arizona.

"We have often seen this banding caused by dew, then frost, followed by a sunny day as the leaf is unfolding from the whorl." -Kent L. Brittan, University of California Cooperative Extension.

I talked to Mr. Ellsworth today and he has informed me that the crop looks completely recovered from the problem.

To contact Marco Peña go to: marcop@ag.arizona.edu.

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.