Taxonomy

Domain	Eukarya
Kingdom	Fungi
Phylum	Ascomycota
Subphylum	Pezizomycotina
Class	Eurotiomycetes
Subclass	Eurotiomycetidae
Order	Eurotiales
Family	Trichocomaceae
Genus	Aspergillus

Scientific Name

Aspergillus flavus

Common Name

Aspergillus ear and kernel rot

Author: Mpoki Shimwela, University of Florida

Reviewed by: Jeffrey Rollins, University of Florida

Pathogen

Aspergillus flavus is a fungal pathogen that causes Aspergillus ear and Kernel rot. The fungus is mostly found in soil as saprophytes, but it has a broad host range as an opportunistic pathogen. It causes significant losses in corn, peanuts, cottonseed, and tree nuts. A. flavus is also a pathogen of animals and insects. Contamination with aflatoxin, a toxic and carcinogenic compound, can occur when the fungus grows on food sources.

Symptoms and Signs

Powdery olive-green (yellow-green) mold grows on the ears of corn and then turns brown as the masses age.

Ecology and Spread

Hot, dry weather condition is favorable for Aspergillus infection and spread. Aspergillus fungal spores are produced on crop residue on the soil surface and on discarded kernels, cobs, and fines around grain bins. The spores are dissemenated by wind and insects to the silks of the maturing ears. After the conidia germinate in the ear, they invade the kernels, usually towards the top of the ears. Injured kernels are most susceptible. Here they produce masses of spores, which are attached externally to the kernel. During its growth, the fungus produces aflatoxin that is undesirable in the harvested grain. The conidia inside the infected kernels mature with the grain. Conidia are included with the grain or cast out with the debris when the grain is harvested, entering into the soil to overwinter until next summer. If the conidia are included with the harvested grain, it causes grain rots.

Geographic Distribution

This pathogen is wide spread, particularly in tropical and subtropical soils.

Management

Use deep tillage to minimize amount of inoculum available in the uppermost part of the soil layer.
Provide enough air circulation in the storage to maintain low moisture and proper temperatures throughout the storage room.
Harvest and store grain from Aspergillus-contaminated fields separately.
Dry grain below 13% moisture for long-term storage.
Avoid insect and bird damage in the field and storage.

Diagnostic Procedures

The fungus grows well on Malt extract Agar.

Diagnostic features include:

conidial heads radiate, splitting into columns;
conidiophores thick-walled, hyaline; and
conidia typically globose to subglobose.

Resources and References

1. Klich, M.A. 2007. Aspergillus flavus: the major producer of aflatoxin. Molecular plant pathology, 8:713-722.

2. Kozakiewicz, Z. 1995. Aspergillus flavus. IMI Descriptions of Fungi and Bacteria, 1995 (No.126) Sheet 1251. Surrey, UK: CABI Bioscience.

Acknowledgements

National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2011-41530-30708 as part of "Diagnostic Image Series Development for Supporting IPM in the Southern Region" (USDA-NIFA-RIPM-003351)