About Diplodia Ear Rot
The causal fungi, Stenocarpella maydis, overwinter in the form of pycnidia in maize residue. In wet conditions, spores are produced and then rain splashed to new plants. Spores germinate down the silks of the plant, eventually infecting the ear. Infection can also occur at the base of the ear through wounds caused by insects and birds. In the three week period after silking, ears are most susceptible to infection.
Diplodia Ear Rot Identification and Habitat
The main symptom of diplodia ear rot is the white, cottony mold on the kernels of the plant. Also, the pycnidia can be identified as small, black specks scattered throughout the husks, kernels, and cobs. In most cases, disease symptoms will appear at the base of the ear, progressing toward the tip. Rarely, the tip-end or middle part of the ear will be affected by the disease. Ears with diplodia ear rot will weigh significantly less than healthy ears. The husks of the plant will likely turn brown and dry out before the rest of the plant. It is uncommon for leaves to be affected.
Within the first three weeks after silking occurs, wet weather is highly favorable for disease development. Early in the season, dry weather followed by abnormally wet weather just before silking can increase chance of infection. Plants in minimum and no-till fields are more susceptible to disease because the spores overwinter in plant residue on the surface of soils, making soil management an important factor in infection.
Diplodia Ear Rot Management and Control Methods
One of the best predictors of diplodia ear rot is the amount of infected residue on the soil surface, making tillage a great way to reduce the chance of further infection. By burying corn debris from the soil surface, spores will break down deeper into the soil, limiting dispersal capabilities. Rotating corn out for a non-host crop will also allow infected plant residue to break down further in the soil. Lastly, always look for resistant varieties of corn to reduce chances of infection and spread of disease.
Foliar fungicides can be used when disease is highly prevalent to reduce stalk cannibalization at grain fill. Before using fungicides, be sure to read labels carefully for cautionary advice and application guidelines.