Regional Crop Update: September 2026

While corn silage and early grain harvest had begun in parts of Iowa, recent and persistent rainfall has brought fieldwork to a standstill across much of the state. In this regional crop update, ISU Extension field agronomists provide harvest progress reports and discuss emerging concerns, including corn standability, ear rots, and grain quality. A weather update at the end also examines Iowa's exceptionally warm and wet September and what those conditions could mean for harvest and crop quality.

Leah Ten Napel (Region 1)

Cherokee, Ida, Lyon, Monona, O'Brien, Osceola, Plymouth, Sioux, Woodbury counties

“Some grain harvest had started in areas of northwest Iowa before the recent wet weather moved in. Several farmers have reported yields higher than they were expecting. Silage harvest also went well across the area, with most fields getting harvested at ideal moistures. The biggest concern for farmers at this point is crop standability. When dry conditions return, prioritizing harvest of fields with weaker stalks will be a key for success. 

Cover crops that were seeded post silage chopping are coming up nicely. The recent moisture should help support continued growth and establishment as we move into fall. Some farmers were still trying to get in their last cuttings of hay; however, the wet weather has made that a bit more challenging. Weather conditions will continue to play a role in how quickly fieldwork progresses over the next few weeks. Waiting for fit conditions before entering the fields with heavy equipment is critical for preventing soil compaction issues down the road.”

Gentry Sorenson (Region 2)

Buena Vista, Clay, Dickinson, Emmet, Hancock, Kossuth, Palo Alto, Pocahontas, Winnebago counties

“Rainfall has been steady over the last few days, making field work difficult. Silage harvest was near completion before the rainfall started with some harvest of corn begun on sandy or lighter soils. At this time, we are a few days out from harvest until the soil conditions improve for field work. Stalk quality is a concern, high winds earlier in the month, persistent recent rainfall and the challenging growing conditions this summer could produce plants with standability issues. As fields start to dry, evaluate corn plants and ears for mold and prioritize harvest based upon compromised fields from stalk or crown rot.”

Josh Michel (Region 5)

Allamakee, Buchanan, Clayton, Delaware, Dubuque, Fayette, Jones, Linn, Winneshiek counties

“Continual rainfall throughout last week and very heavy rainfall over the weekend has led to severe flooding across many areas of northeast Iowa. While most of the region received at least 3.5 – 5 inches of rain over the past week, several areas have received up to 8 inches. All but a few corn fields have reached black layer, while soybeans are mostly R7-R8. Before all the rainfall last week, corn silage harvest was nearing completion. Some early-planted and storm-damaged corn fields were getting harvested for grain. The last alfalfa cuttings for the season were also getting harvested. Recent field calls have centered around silage management and grain quality. Ear rots and stalk rots will be a growing concern."

Rebecca Vittetoe (Region 8)

Iowa, Jefferson, Keokuk, Poweshiek, Washington, Johnson counties

“Like the rest of the state, we are wet. Rainfall totals in the last seven days range from 2 to more than 6 inches. The heavy rainfall pushed some of the creeks and rivers out of their banks over the weekend, causing flooding in areas, including some crop fields. Prior to the wet weather, harvest was getting underway with corn silage as well as some corn grain harvest. As we wait for the weather to cooperate and for fields to be able to dry out, stalk quality and ear molds are something to keep on your radar. Questions recently have been on soil fertility considerations for next year, how late can you cut alfalfa, and concerns about the wet conditions.” 

Virgil Schmitt (Region 9)

Cedar, Clinton, Des Moines, Henry, Jackson, Lee, Louisa, Muscatine, Scott counties

“During the last 30 days, counties I cover received 4 to over 8 inches of rain except parts of Des Moines and Lee Counties received a little less and northern Jackson County received over 10 inches of rain. Corn is nearly all mature and a few fields have been harvested for silage and grain. There are some stalk quality issues in some fields, so stalk quality of each hybrid in each field should be monitored to help establish the order in which fields are harvested once we can get back in the field. The wet weather is also promoting some ear molds, so grain quality should be monitored closely to also help establish the order of harvest. Soybean fields are mature or nearly mature. I have not seen any harvested soybean fields. In most places, it is “soupy” in the field. Farmers should be as patient as possible before harvesting to minimize soil compaction issues.” 

Logan McCrea (Region 11)

Appanoose, Davis, Lucas, Mahaska, Marion, Monroe, Van Buren, Wapello, Wayne counties

“Much like the rest of the state, it has remained wet over the past week or so keeping harvest activities to a minimum. This week doesn't appear to look much different, and we will need plenty of sunshine and dry weather to get to field conditions where harvest can resume/begin. Prior to the wet weather, there was a good chunk of corn silage that was harvested and a handful of fields harvested for grain. Yield reports were variable though the sample size isn't very large yet. There likely would have been some soybean fields ready for harvest last week had it not begun raining, so they will wait for some drier days as well. On the bright side, pasture grass growth is tremendous at the moment given the cool, wet weather. 

One thought that comes to mind regarding a wet harvest is that there may be an uptick in semis being loaded on the road vs in the fields (if field conditions stay wet), making it even more important this year to slow down and be aware of things around you. Take some extra time to get to your destination and be courteous to those around you, everyone would like to make it home at the end of the day.” 

Weather Update - Warmth, Rainfall and Harvest Implications

Justin Glisan, Dennis Todey, and Madelynn Wuestenberg 

"So far, September 2026 has been exceptionally warm and wet across the state. As of September 21, average statewide precipitation is 6 inches, which is around 2.5 inches above normal, and makes this September already the 6th wettest on record, with 9 days left in the month. At this time, statewide average temperatures for September are 7 degrees warmer than normal, putting us on track for the warmest September on record. 

This perpetual rainfall pattern is driven by Gulf and Pacific monsoonal moisture converging over Iowa. There is a lack of steering winds and flow aloft and plenty of precipitable water, leading to training thunderstorms with sufficient moisture available. Very strong El Niño conditions have hindered tropical activity, keeping us in a stagnant pattern.

While September 2019 serves as the closest analog for statewide rainfall totals, the agricultural impacts are different. In 2019, the primary challenge was delayed crop development following a late planting season, with corn and soybean maturity running roughly two weeks behind normal. This year, crops are more advanced and growing degree days have been ahead of normal for most of the growing season, but the combination of record warmth, exceptionally high humidity, and frequent heavy rainfall is shifting concerns toward grain quality, including ear rots, mycotoxins, stalk rots, flooded grain, reduced forage quality, and soil compaction. In many respects, 2019 was a maturity problem, but this year the main concern is grain quality."