By Luke Schulte, Beck’s Hybrids
Unfortunately, like last fall, gibberella ear mold has been seen in numerous corn fields amongst a multitude of hybrids. While diplodia, aspergillus, and fusarium are also examples of common ear molds, gibberella is typically the most common and often results in the production of harmful mycotoxins or vomitoxin.
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 most all fields but is especially abundant in corn following corn or corn following wheat and fields with a history of gibberella. Infection primarily enters the ear via silk channels, particularly the straggler green silks remaining after pollen shed has concluded. The fungus will attach and grow down the silk to infect the ear. Any stress that hinders pollination has the potential to impact gibberella/vomitoxin levels — insufficient N, heat throughout pollination, drought.
Likely the most significant factor to impact gibberella infection is moisture 6 to 21 days after silking. Research from Ohio State University has found, relative humidity above 80% during this timeframe has shown some of the strongest correlations to vomitoxin contamination. This is why gibberella is also more common in later planted corn. As days get shorter and night length increases, the crop canopy remains wet, later into the day.
Lastly, hybrid differences exist as well. The silks of some hybrids are more susceptible to infection than others.
Minimizing vomitoxin (VOM) within the sample
The majority of the mycotoxins or VOM are within the fines and bees’ wings. According to an Ohio State University grad student, whose research project consisted solely to 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 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, remove door
• There is a beneficial video explaining the above modifications at: youtube.com/watch?v=Wt7tZHmZHM4&t=334s
• Harvest infected corn when fodder is dry
• Utilize grain cleaner- before/after dryer
Storage and drying
• Core bins immediately
• Utilize grain cart upon loadout- additional handling may allow for wind to remove fines/bees’ wings
• Store grain ≤ 15% moisture to prevent further fungal growth
• Dry immediately- within 48 hours of harvest
• Store grain at 36 degrees 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
• When hauling stored grain deliver grain harvested at higher moisture first because additional fines were likely created during shelling
• Haul early- warm, moist pockets within storage will grow
• End-users will vary on VOM allowance
• Feed mills, ethanol production will likely be more restrictive
As harvest nears completion, implementation of the management practices above may help to minimize the headaches of dealing with mycotoxin-infested grain throughout the duration of storage.