Don’t forget about the less savory September surprises — ear and stalk rots silently spoiling a hard-earned corn crop.
“It’s something we want to watch for,” said University of Nebraska Extension plant pathologist Tamra Jackson Ziems. “Anything that causes wounding, such as bird or insect feeding, could lead to development of some of these fungal diseases.”
On the top of the list of likely culprits this year are ear rots such as Diplodia, Fusarium and Gibberella and common stalk rots such as anthracnose, charcoal rot and Fusarium stalk rot, Ziems said.
STALKING YOUR CORN
“I’m actually most concerned about stalk rots this year just because the crop has had a lot of stress throughout the season,” Ziems said. “At first there was too much moisture and then it became dry toward the end of the season.”
Ziems has noticed some Nebraska cornfields appear to be dying backwards, with uppermost plant leaves turning yellow and drying down first. That “top die-back” is a classic sign of anthracnose. “It could lead to some yield loss or tops breaking off the plants with wind,” Ziems said.
Anthracnose can be identified fairly definitively by the presence of shiny black lesions on the stalk behind the leaf sheaths, according to a University of Nebraska stalk rot guide.
Although no reports of Fusarium stalk rot have trickled into her office yet, it is the most common stalk rot in Nebraska, and it often occurs alongside other ear and stalk rots. Charcoal rot also could be a threat this year, Ziems said.
Confirm stalk rot damage by shoving your corn plants around a bit. Walk through multiple sections of the field and shove plants firmly down as you go; a 30- to 45-degree-angle shove will do. “You’re basically simulating pressure caused by wind,” Ziems explained.
“A good healthy plant with a strong stalk will snap back upright,” she said. “But with stalk rot, they will bend down below the ear. If you have over 10% bending and not snapping back, that field is at high risk for lodging.”
Put those fields at the top of your harvest list and consider harvesting them earlier than usual, Ziems advised. Early harvesting does mean higher grain drying costs, but yield losses from lodging and the extra time it takes to harvest a field full of fallen plants should be weighed as well, she said.
For a comprehensive list of stalk rots and their symptoms, see this Nebraska guide:http://bit.ly/….
WATCH YOUR EARS
Ear rot reports are starting to pick up in Michigan, according to University of Michigan plant pathologist Martin Chilvers. He encouraged growers to watch for Fusarium and Gibberella ear rots in a recent Extension article. Diplodia ear rot is also a common culprit in the Midwest.
You can find a comprehensive list of ear rots and their symptoms from the Crop Protection Network, an information service produced by a consortium of Canadian and American university crop scientists: http://bit.ly/….
Chilvers recommends completely husking 20 ears in five different spots in a field, for a total of 100 ears per field when scouting.
One of the more serious concerns from ear rots is the presence of mycotoxins. Fortunately, the most dangerous mycotoxin-producing ear rot, aspergillus, is most common in drought conditions, which most producers did not experience this year, Ziems said.
The Crop Protection Network released an updated mycotoxin guide, including toxin source, dangers, accepted levels and how to manage the risk they pose humans and livestock. You can find it here: http://bit.ly/….
If possible, don’t store grain from fields with significant ear rot problems, Ziems advised. If you must store, short-term storage will require drying grain down below 15% moisture, and long-term storage will require under 13% moisture and keeping winter grain temperature around 30 degrees, Chilvers said.
For more information on storing mycotoxin-affected grain, see this guide from the Crop Protection Network: http://bit.ly/….