Weekly Scouting Report - September 10, 2014
Hello! We are starting our 3rd trip through corn this week. I have noticed two things in the corn I have scouted. One is the presence of ear molds, the other is anthracnose in the upper part of the plant. The yield checks we are very good. Ear consistency is very good with size differences occurring in different soil types. Low areas and low CEC areas are showing nitrogen deficiencies and that’s where I am seeing stalk issues. Below are examples of anthracnose and different ear molds.
Gibberella ear rot is caused by the fungus Gibberella zeae, also known as Fusarium graminearum. It usually begins at the tip of the ear and appears red or pink, or occasionally white. Gibberella sometimes rots the entire ear. Infections occur more commonly in cool, wet weather after silking and through the late summer. Gibberella can produce vomitoxin and zearalenone.
Fusarium ear rot is the most common fungal disease on corn ears. It is caused by several species of Fusarium. Symptoms of Fusarium ear rots are a white to pink- or salmon-colored mold, beginning anywhere on the ear or scattered throughout. Often the decay begins with insect-damaged kernels. Usually it does not involve the whole ear. Infected kernels are often tan or brown, or have white streaks. These fungi can produce mycotoxins known as fumonisins.
Diplodia fungus initially appears as a white mold beginning at the base of the ear. The mold and the kernels then turn grayish brown and rot the entire ear. A very distinguishing characteristic is the appearance of raised black bumps (pycnidia) on the moldy husk or kernels. Diplodia ear rot occurs most often in fields under reduced tillage where corn follows corn.
Aspergillus flavus can produce aflatoxins. It is an olive-green, powdery mold. In Iowa, Aspergillus is much more common in hot, dry years. The fungus can be detected in corn because it produces compounds that are fluorescent under black light, but this method does not directly detect the presence of aflatoxins.
Cladosporium fungi often infect kernels damaged by insects, hail, or frost. Cladosporium appears gray to black or very dark green and can have a powdery appearance.