Written By Dr. Gene Milus
There appears to be several possible causes of white heads showing up in central and northeast Arkansas wheat. In one case, the heads are dead and white coming out of the boot, but the stem and the leaves are still green and healthy. These white heads may be caused by freeze damage that occurred within the last two weeks, although it didn’t seem like it got cold enough to cause problems.
Symptoms of freeze damage vary greatly depending on the growth stage when the freeze occurred, and it takes several days to a week or more after the freeze event for symptoms to become evident. The links below are to publications on wheat freeze damage that have pictures of the various symptoms.
In some cases of dead heads coming out of the boot, the peduncle (stem below the head) is also dead. Some plants with this symptom were found to have sharp eyespot lesions on the lower stem. See the link below for information on sharp eyespot.
The third case involves white heads in which the entire stem, or most frequently, the entire plant is dead. These symptoms are likely caused by Bipolaris or Fusarium fungi that infect roots, crowns, and lower stems. The diseases are called common root and foot rot, dryland root and foot rot, or Fusarium root, crown and foot rot. These diseases are common in regions of the Great Plains and the Pacific Northwest where wheat frequently experiences drought stress during grain fill. Wheat roots in Arkansas likely are infected by both of these fungi every year, but disease symptoms (prematurely dead plants) only occur when the plants are drought stressed after heading. Low water potential in the plants triggers the fungi to grow up infected roots into the crown and lower stems, killing the plant. Where these diseases are common, the recommended management practices are to rotate crops, use moderately resistant varieties, and to reduce seeding and fertility rates so that there are fewer and smaller plants competing for available water. In Arkansas, our normal seeding and fertility rates are optimized for “normal” precipitation that does not cause drought stress. When precipitation is less than normal, the large number of big plants use up the available water and cause drought stress. The link below is to an informative Australian publication that is applicable to our situation.
Patches of dead plants could be caused by take-all, but no take-all has been documented in Arkansas yet this year. The link below has a publication on take-all in Arkansas.