It is SPRING and it is that special time when wheat problems begin coming in to the Delta Center. The wheat at left was brought in by a farmer from North Pemiscot County. The samples brought in were excellent. The wheat plants were clean and intact (including roots). A plastic bag works fine, but this gentleman set up the plants in damp paper towels in a drinking glass – the samples looked field fresh four days later! As you can see the plant has awful looking lesions and the worry is that a yield-robbing wheat disease may be in this field.
Dr. Wrather (http://plantsci.missouri.edu/faculty/wrather.htm) is our plant pathologist and very good at troubleshooting these kind of problems. Dr. Wrather follows a six step program to figure out what is happening just like he teaches at scouting schools, grower meetings, and even the trouble shooting document he helped MU extension produce (http://extension.missouri.edu/publications/DisplayPub.aspx?P=G4050).
1. Determine the variety and the age of the plant.
2. Identify all symptoms affecting the leaves, stems, roots and fruit.
3. Estimate the percentage of plants damaged in the affected part of the field and the severity of damage.
4. Determine the field distribution or pattern of the problem in the field.
5. Evaluate whether other plant species (weeds) in the field share similar symptoms.
6. Determine the history of the problem.
For this wheat, it was found that the lower leaves and the newer leaves do not exhibit the problem. This pattern of occurrence leads one to think the problem is herbicide drift. The lower leaves were shielded by the upper leaves, and the younger leaves have unfurled since the herbicide drift happened so they didn’t have contact with the herbicide = no damage. Of course, a field visit is the gold standard and will allow determination of patterns and examination of weeds (in field and ditches) for similar lesions to confirm the diagnosis. IN CASES OF ECONOMIC INJURY FROM PESTICIDE DRIFT WHERE ABSOLUTE DETERMINATIONS MUST BE MADE CONTACT THE MISSOURI DEPT. OF AGRICULTURE BUREAU OF PESTICIDE CONTROL: (573) 751-0005 (http://mda.mo.gov/plants/pesticides/pesticides.php).