A cold front stalled over much of the Midwest this week, stretching from the Nebraska–Kansas border to the southern Great Lakes, with repeated rounds of rain — from under an inch to more than 4 inches in places — forecast through Thursday 17 September, DTN ag meteorologist John Baranick said, while areas south of the front from eastern Kansas through the Ohio Valley stay hot in the 90s. "The persistent wet pattern will do little to ease concerns about corn ear quality, which could worsen in some areas where crops are already showing signs of damage," he said.

In Kansas, ear rot and mould are the main problems as corn matures and harvest begins. "I've been getting a lot of calls on a variety of ear molds that are progressing," said Logan Simon, south-west area agronomist at Kansas State University, who has been finding Fusarium ear rot, Aspergillus ear mould and Diplodia ear rot in fields. "With the rain and hot and humid weather, that is only going to increase the mold." Fusarium and Diplodia thrive in warm, wet weather after silking; Aspergillus is driven by hot, dry conditions.

Scouting before harvest is essential, Simon said, so that farmers can reorder harvest priorities and segregate affected grain: many ear-rot fungi produce mycotoxins that harm livestock fed silage or distillers grains, and contaminated grain is hard to market and may be docked or rejected. Moulds also lower test weight and raise grain moisture, so corn going into storage should be dried quickly to 15% or less.

Sprouting on the ear — kernels germinating before harvest — is the other worry, driven by delayed silking, hail, insect injury, late rain, warmth and upright ears, and more likely when grain already below 20% moisture is re-wetted. Dave Walton, who farms near Wilton in south-east Iowa, scouted about 200 acres on 12 September and found several ears sprouting or mouldy. "It's something to watch, especially with the wet week ahead," he said.

Ryan Gentle, Wyffels Hybrids agronomy manager for western Illinois, has not seen widespread problems but says husks are drying and opening, raising the risk: "When you get an inch or two of rain after that happens, you can start having problems. Scout now, and not just the end rows." Fields with substantial sprouting should be harvested as soon as possible and dried at slightly higher temperatures to 15% or less. Crown rot remains his region's chief concern — fields hit hard yielded under 200 bushels an acre where 230 to 260 was expected, worst in early-April plantings of early maturities.

Source: DTN/Progressive Farmer