By Matt Reese
There have been reports of farmers getting sick from cleaning combines without wearing dust masks. This could be linked to the inhalation of dust from a number of different ear rots that are being discovered in the Ohio corn crop.
Ear rots in fields can present health and safety issues during and following harvest. Corn harvest and grain handling become very important when ear rots are an issue.
AgriGold agronomist John Brien pointed out a number of potential ear rots in Ohio this fall to watch for in fields.
Fusarium kernel rot
Fusarium is caused by several different species of Fusarium and is the most common fungal disease on corn ears. The Fusarium pathogen overwinters very well on corn and grass residue and is more often seen in no-till, minimal-till and continuous corn fields. The Fusarium fungus thrives in environments that are hot and dry after pollination. The pathogen is also amplified by drought stress at silking.
Typically Fusarium kernel rot is found on scattered kernels or in small groups of kernels
throughout the ear. It is identified by whitish pink to lavender “fuzz” that covers the kernels. Often only kernels that are damaged due to insect feeding or silk cutting are prone to a Fusarium infestation, but under ideal conditions undamaged kernels can be infected. Ears that remain upright during heavy rainfall events and/ or have poor husk cover tend to be more susceptible to extensive rotting.
Gibberella ear rot
Gibberella is recognized by a pink, red or deep red mold that develops from the ear tip and progresses towards the base of the ear. Corn husks will often adhere tightly to the ear and a pink to red mold will grow between the husks and ears. The pathogen that causes Gibberella ear rot overwinters on infected crop residue. Both corn and small grain residue are carriers.
Gibberella spreads from the crop residue unto the corn silks via splashing rain water and infects the corn ear. The disease is more severe when cool, wet weather occurs within the first 21 days after silking. The ear rot is more severe when water collects between the ear and the husk. A hybrid with a tight style husk is more susceptible to Gibberella ear rot than a loose-husked hybrid. If there is concern, take a 10 pound sample and have it tested prior to feeding to livestock.
Diplodia ear rot
Diplodia is caused by the fungus Stenocarpella maydis and can be identified by the thick white mold that starts at the base of the ear. The white mold will ultimately change to a light gray color or brown over the husks and kernels. One visual symptom of infection is the early appearance of a bleached or straw colored
husk with raised black fruiting bodies late in the season if infection occurred early.
Corn is the only known host for this fungus. The fungus overwinters on corn residue. Due to this, corn on corn acres and reduced or no-till acres are at a greater risk of infection. Infection by Diplodia is enhanced by dry weather prior to silking, followed by wet conditions at and just after silking. Ears are most susceptible to this disease during the first 21 days after silking. Insect damage generally associated with corn borer and corn ear worm may also allow for a point of entry and cause the damage to be accentuated. Damage caused by diplodia reduces test weight and yield along with lower nutritional value of affected grain. There are no known mycotoxin problems associated with diplodia ear rot and therefore no feeding restrictions.
This can be identified as an olive green or yellowish green powdery fungus on drought stressed corn ears. The fungi survive on plant residue and produces abundant spores. These spores are then carried by wind to infect silks and damaged kernels. Short husks that expose ear tips are more susceptible to kernel damage from insects and weather, therefore more prone to infection by Aspergillus.
The major concern with Aspergillus is its ability to produce aflatoxins. Aflatoxins are naturally occurring by-products produced by two types of molds: Aspergillus flavus and Aspergillus parasiticus. Aspergillus flavus is the most common and
often found when corn is grown under stressful conditions such as drought. Aflatoxins are harmful and can cause several problems in livestock, most commonly a reduction in feed efficiency and reproductivity, suppression of immune system, and in rare instances, death. The most abundant aflatoxin, aflatoxin B1, is a carcinogen. This raises human health concerns because aflatoxin can appear in the milk of dairy cows fed contaminated corn.
Brien urged farmers with possible ear rot issues to harvest problem fields as soon as possible.
“The general guideline is if 10% of the ears in the field have at least 25% of their kernels infected, early harvest is warranted,” Brien said. “The ideal harvest moisture for fields with kernel rots is 25% to 27% moisture. If a grower is going to store grain contaminated with kernel rots, they should dry the grain to below 15% as quickly as possible and then cool the grain to below 50 degrees soon after drying and try to store the grain in the bin below 30 degrees.”