Understanding gibberella ear mold, minimizing vomitoxin

By Luke Schulte, Beck’s Hybrids

Fall provides the culmination of the growing season and often the reward for our year-long efforts. However, ear molds and poor grain quality dampen our enthusiasm and make for some lingering challenges if not dealt with properly both at harvest and prior to grain storage.

Some common ear molds, such as diplodia, are not known to produce mycotoxins. However, aspergillus, fusarium, and gibberella ear mold often result in the production of harmful mycotoxins. While aspergillus and fusarium are less common, gibberella is all too often present within some fields at harvest. Gibberella ear mold can lead to vomitoxin present in the grain, which can cause health problems in both humans and livestock, particularly swine. 

What causes gibberella ear mold and why does it occur?

Gibberella ear mold is caused by the fungus fusarium graminearum. This fungus is present to some degree in almost all fields but is especially abundant in corn following corn or wheat and fields with a history of gibberella. Initial infection primarily enters the ear via silk channels. Moisture and/or cool weather for the two to three weeks following silking promote infection. Heat stress throughout pollination can also enhance infection. During times of significant pollination heat, the silks attached to the tip of the ear will not get fertilized and remain green. After pollen shed, these green silks serve as the transportation vehicle for the fungus to enter the ear as the fungus no longer has competition from pollen grains, which is why gibberella often begins near the tip of the ear. Infection is also more common in late/later planted corn due to more abundant moisture within the crop canopy as a result of shorter days and longer nights during early reproduction. Hybrid differences exist as well as the silks of some hybrids are more susceptible to infection than others.

Minimizing vomitoxin in samples and storage 

The majority of the mycotoxins or VOM are within the fines and bees’ wings. According to an Ohio State University graduate student whose master’s degree project consisted of the understanding and management of gibberella ear mold, “they’ve never seen gib in the grain without being in the cob as well.” Bees’ wings are a component of the cob, so their removal is critical.

Harvest/removal of fines/bees’ wings in combine settings and modifications:

• Utilize fan speed to “blow” out shriveled/damaged kernels
• Perforated screen under clean grain elevator
• Perforated screen under return elevator, if very high VOM levels, than remove door
• There is an excellent video explaining the above modifications at https://www.youtube.com/watch?v=Wt7tZHmZHM4&t=334s.

In addition, infected corn should be harvested when fodder is dry. Also, utilize a grain cleaner- before/after dryer.

For storage and drying:

• Core bins immediately 
• Utilize grain cart upon loadout as additional handling allows for wind to remove fines/bees’ wings
• Dry/store at less than 15% moisture to prevent further fungal growth
• Dry immediately (within 48 hours of harvest)
• Store grain at 36 to 44 degrees F and maintain aeration. 

Prioritize and designate:

• Harvest infected fields as early as possible to limit fungal growth on the ear
• Segregate infected grain if possible

For hauling stored grain, deliver wetter harvested grain first as additional fines were likely created throughout harvest. Haul infected grain early, as warm, moist pockets within storage will grow. Different end-users will vary VOM allowance with feed mills and ethanol producers likely being more restrictive.  

In an ideal world, hybrid selection would eliminate this problem from reoccurring. However, the likelihood of this taking place short term isn’t probable. Stay tuned this fall for the results of a joint research project we are conducting with Ohio State University at the Beck’s London, Ohio PFR facility for some innovative concepts regarding more effective management of this disease moving forward.