Diplodia overwinters on corn debris; therefore, corn-on-corn fields managed with reduced tillage have an increased potential for Diplodia stalk and ear rots Figure 1. Management of Diplodia stalk rot is through use of resistant hybrids, balanced soil fertility, appropriate plant population for the hybrid selected, and crop rotation. Diplodia grows around the kernels and infects the pith, resulting in reduced grain quality and compromised stalk integrity. Inheritance of resistance to Diplodia zeae in eight populations of corn was studied. The fungus overwinters in corn debris; therefore, corn-on-corn fields managed with reduced tillage have an increased potential for Diplodia stalk and ear rots. Generation mean analyses were used to detect the types of gene action important in host resistance to stalkÔÇÉrot of corn caused by D. zeae.Six of 8 populations studied consisted of P 1, P 2, F 1, F 2 B 1, and B 2 generations. Tiny black specks (pycnidia) embedded in rind of lower stalk; Lower, inner stalk may have shredded tissue and small, dark specks (pycnidia) Pathogen Involved. The identifying characteristic of Diplodia stalk rot are tiny black specks (pycnidia) buried in the outer rind of the stalk at the lower nodes (Fig. consider Diplodia stalk rot as either an air-borne or a soil borne disease. Diplodia stalk and ear rot are caused by the fungus Stenocarpella maydis. Physoderma brown spot most commonly causes a leaf disease, but under some conditions can cause stalk rot disease. Diplodia stalk rot has been observed in central Iowa. Diplodia Stalk Rot Facts: Caused by Stenocarpella maydis fungus (formerly called Diplodia maydis) Corn is the only host of this pathogen; Survives on corn stalk residues; Spores are spread by wind or splashing rain; Favored by warm, wet weather two to three weeks after pollination Timing: Stalk infections most often occur through the It is more severe where corn follows corn. Diplodia Stalk and Ear Rot The fungus responsible for Diplodia stalk rot (Stenocarpella maydis) survives only on corn residue, placing continuous cornfields at the highest risk for infection. White mycelium can develop in lower stalks. Symptoms may be similar to those of Gibberella stalk rot, but Diplodia doesn't develop pink color. Stalk rot results in premature plant death. Stalk rots may result in premature death of plants (Figure 1) or reduced yield potential. "Hence, tillage is effective, but if tillage is not practical, less susceptible hybrids and rotation to non-host crops are recommended for Diplodia. The fungus causing Diplodia stalk rot reproduces with microscopic spores inside minute raised black structures (pycnidia) that can give the stalk a rough/sandpaper-like feeling (Figure 3). Figure 1. In 2013, the Corn Disease Working Group estimated that the corn producing regions of the United States and Ontario, Canada had losses of 7.9 and 12.0 million bushels of corn from the Diplodia stalk rot and ear rot phases of the disease, respectively. Two populations had an additional generation, a composite F 3. In general, stalk rot development is favored by This stalk rot is easily recognized: Look for minute black specks (pycnidia) buried in the rind of the lower nodes of the corn stalk (Figure 2). Diplodia stalk and ear rots are caused by the fungus Stenocarpella maydis. Diplodia may be mistaken for Gibberella stalk rot because of the black specks; however, the black specks associated with Gibberella stalk rot can be easily scraped off with a thumb nail. 3, below). 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