Take-all is a chronic root-disease problem in Illinois wheat production. It is a crown and foot rot caused by the soilborne fungus Gaeumannomyces graminis, not a disease for the spelling challenged. Typically the disease affects fields that have been in wheat for 3 to 6 years, where the soil tests neutral to alkaline, the soil is sandy, or where the soil may be deficient particularly in nitrogen or phosphorus. |
Take-all in low N and adequate N environment. (Courtesy of R. Bellm.)
The disease also prefers compacted poorly drained fields where moisture is not in short supply.
Yield losses will depend on how severely the roots and culms are infected and how early the disease showed up. Early-season infections can result in up to 50% loss.
Symptoms are quite recognizable at heading. Infected plants usually show up in localized patches in a field, and heavily infected plants appear light green and somewhat stunted, and will ripen and die prematurely. Infected plants develop sterile or nearly sterile white heads with a few or no shriveled kernels. The field diagnostic symptom, though, is present on the base of the stem. Peel back the leaf sheath of the lowest leaf and you will see a superficial covering of shiny black fungus.
Black mycelial mat of takeall. (Courtesy of R. Bellm.)
Don't get too carried away with field pattern for this disease. It can show up in the more typical patches, or an entire field can be affected, or, as a few people know I have been stymied by, it can follow very subtle pH changes in a field and mimic spray damage. So I urge you to look for the blackening of the culms when you make your diagnosis and to gather some information on the soil condition.--Suzanne Bissonnette