Dealing with Diplodia
Emily Unglesbee DTN Staff Reporter
Fri Oct 17, 2014 03:23 PM CDT
(Page 1 of 2)

ST. LOUIS (DTN) -- Farmers' damp spirits are not the only victims of the recent rainy weeks. Your corn ears might be feeling rotten, too.

Many farmers are seeing corn ear rots like Diplodia, which will require careful handling come harvest and storage time. (Photo by Charles Woloshu, Purdue University)

The late summer and fall weather have provided the perfect conditions for the common ear and stalk rot fungus Diplodia, plant pathologists told DTN.

In parts of western and southern Illinois, soggy weather has produced increasing reports of Diplodia in cornfields, University of Illinois Extension educator Dennis Bowman said.

Diplodia has also been reported in many fields in Iowa. "We had perfect weather for the disease -- cool and wet," Iowa State plant pathologist Alison Robertson noted in an email. Growers should also be on the lookout for other ear rots such as Gibberella and Fusarium, which can produce dangerous mycotoxins, she added.

Although Diplodia isn't known to produce mycotoxins, the disease has important implications for harvest and grain management, so growers should still scout for it, University of Illinois Plant Diagnostic and IPM coordinator Suzanne Bissonnette told DTN.

"It's a quality issue, and a yield issue," she explained. The white, fluffy mold, which often starts at the bottom of the corn ear, robs the kernels of their weight. "When you hold an ear infected with Diplodia in your hand, it weighs almost nothing," Bissonnette noted.

If you have ear molds in your cornfields, consider sending them into your university's plant diagnostic clinic, she said. Elevators will test your grain for mycotoxins and dock you if they find some.

"That's where we come in," Bissonnette explained. "By testing, you can have some confidence going into the elevator that the mold isn't Fusarium and Aspergillus."

Even if you didn't see ear molds in earlier-season scouting trips, check again, Bissonnette urged. Your standing corn can still be at risk. "If you had any damage to the tip, say from birds or insects, and the ears are upright, water can more easily get into the ear," she explained. "That would present the ideal situation for infection."

If your scouting reveals a field with more than 10% of plants sporting moldy ears, harvest it as soon as possible and dry it down quickly, Robertson said.

Drying corn to below 15% moisture is the safest bet, particularly if you are looking at long-term storage of your grain, Bissonnette added.

"When fungi are active in storage, they respire, which produces moisture, so then other fungi can become a problem in storage," Bissonnette explained.

When drying your corn, either with cold air or heat, "try to damage the grain as little as possible, so you produce as few cracks as possible and don't give entry to any spores that might be hanging around," she added.

This year's record corn crop will likely force some farmers to resort to secondary storage options such as equipment sheds, barns, livestock buildings, or even covered piles.

These less-than-ideal storage conditions will only exacerbate the problem of moldy corn, and keeping the grain dry and clean will be even more important, Bissonnette noted.

"Wherever there is going to be excess storage, those areas need to be as clean as possible when the grain goes in -- you don't want to give any opportunity to fungi already in the temporary storage unit," she said. "Being exposed to cold air is OK, but you don't want to be introducing moisture," she added.

Looking ahead, growers can opt to rotate to soybeans or look for hybrids with some resistance to ear and stalk rots. However, the diseases are so dependent on weather conditions that pre-emptive management is difficult, Bissonnette noted.

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