UF/IFAS Corn Ear Rot Identification and Management

Introduction

Corn ear rot fungi have the potential to reduce yield and grain quality when incidence and severity are high. The fungi responsible for these rots can produce secondary metabolites (mycotoxins) that can lead to poisoning in livestock and humans, if consumed. Heavily infected ears/grain may result in price dockage or even rejection at the buying point. There are five common ear rot fungi responsible for these diseases. Their identification and management are discussed in the following.

Disease Descriptions

Penicillium Ear Rot

Causal agent(s): Penicillium spp.

Symptom description: Spores are blue-green and have a dusty appearance.

Mycotoxins produced: Several less common mycotoxins

Penecillium Ear Rot. Photo Credit: Tamra Jackson-Ziems, University of Nebraska-Lincoln.

Fusarium Ear Rot

Causal agent(s): Fusarium verticilloides, F. proliferatum, F. subglutinans

Symptom description: Infection occurs around silking. Infection is not associated with the tip or base of the ear, it can occur anywhere on the ear.

Mycotoxins produced: Fumonisin, Vomitoxin (DON)

Starburst pattern as a result of Fusarium infection. Photo Credit: Tamra Jackson-Ziems, University of Nebraska-Lincoln.

Fusarium Ear Rot. Photo Credit: Tamra Jackson-Ziems, University of Nebraska-Lincoln.

Gibberella Ear Rot

Causal agent(s): Gibberella zeae (sexual stage of F. graminearum)

Symptom description: Red mat of mycelium that may turn white, typically arising from the ear tip and working toward the base. Infected kernels may develop small black dots (perithecia).

Mycotoxins produced: Vomitoxin (DON) and Zearalenone

Gibberella Ear Rot. Photo Credit: Tamra Jackson-Ziems, University of Nebraska-Lincoln.

Diplodia Ear Rot

Causal agent(s): Diplodia maydis (syn. Stenocarpella maydis)

Symptom description: A thick, white mat of mycelium is produced, typically arising from the base of the ear and working toward the tip. Small black dots (pycnidia) will eventually develop on the kernels.

Diplodia Ear Rot. Photo Credit: Tamra Jackson Ziems, University of Nebraska-Lincoln.

Aspergillus Ear Rot

Causal agent(s): Aspergillus flavus, A. parasiticus, Aspergillus spp.

Symptom description: Spores olive green or yellow green. Infection occurs at the ear tip or in association with ear wounds.

Mycotoxins produced: Aflatoxin

Aspergillus Ear Rot. Photo Credit: Tamra Jackson-Ziems, University of Nebraska-Lincoln.

Management

Cultural Practices

The best management practice for reducing corn ear rot diseases is reducing the amount of infectious fungi in the environment. This can be done via crop rotation, planting resistant varieties, and tillage of infected residue. Keeping your corn healthy is also important to reducing infection. This includes proper irrigation timing and nutrient management. Post harvest, it is important to follow proper grain storage practices (low moisture).

Factors leading to infection:

high planting population
high inoculum load
planting susceptible hybrids
corn on corn production

Chemical Control

Unfortunately, the use of foliar fungicides has not been shown to decrease disease incidence or severity.