This summer corn growers in west central and southwestern Minnesota noticed a high percentage of barren stalks and abnormal ear development in some fields. Corn growers and local seedsmen reported 30-40 percent barren stalks in some fields. We surveyed multiple locations for barren stalks in fields along a 50-mile path from Bunde to Madison. The fields surveyed were variety demonstration trials where hybrids from different companies could be compared side-by-side under similar field and environmental conditions. The highest percent of barren stalks observed in the survey was 17 percent; not as high as observed in some commercial fields in the same area. The occurrence of barren stalks was not limited to any particular company's hybrids.
Reddish-purple plant leaves and stalks
We collected corn plants exhibiting multiple ears per stalk, barren stalks, and healthy plants during our survey of variety demonstration plots and from several commercial fields. Pith tissue from those plants was cultured on acidified-PDA agar to identify the organism in the affected vascular tissue. The isolated tissue produced mostly Fusarium species of stalk rotting fungus. Cephalosporium acremonium was not isolated from any of the affected stalks; thus, the condition described above was most probably not due to black bundle disease as described by Reddy and Holbert (1924).
This condition is not uncommon in many different hybrids. Complexed sugars in the leaves and stalks of barren plants are not transported out of the tissues to the developing ear because there is no ear. As a result, when the chlorophyll in the leaves and stalks break down during senescence, the sugars remaining in the tissue express a reddish-purple color. This is similar to what occurs in tree leaves in the fall.
Barren stalks and small nubbin ears
Pollination time in much of the state this past summer was characterized by limited precipitation and by high ambient temperatures, ranging in the high 90's. It was not uncommon for poor pollination to occur, resulting in some barren stalks and nubbin ears in most, if not all corn hybrids.
Multiple ears per node on a stalk
Darkened vascular bundles in the pith of the stalk
In conclusion, the above mentioned conditions, or symptoms, observed in corn this season were not the result of the disease called Black Bundle since the causal organism responsible was not found. Rather, the set of symptoms observed in corn were probably due to an interaction of corn genotype with a specific set of adverse environmental conditions. The chances that the same set of specific conditions occurring in the future are minimal. Regardless of the exact cause of the symptoms the end result was barren stalks in corn.
Harris, M.R. 1936. The relationship of Cephalosporium acremonium to the black bundle disease of corn. Phytopathology 26:965-980.
McGee, D. C. 1988. Maize diseases, a reference source for seed technologists. The American Phytopathological Society: St Paul, MN. 150 pp.
Nyvall, R. F. 1999. Field crop diseases. third edition. Iowa State University Press. Ames, IA. 1021 pp.
Reddy, C. S. and J.R. Holbert. 1924. The black-bundle disease of corn. Journal of Agricultural Research 27:177-205.
Shurtleff, M. C. (ed.). 1980. Compendium of corn diseases, second edition. The American Phytopathological Society: St Paul, MN. 105 pp.