The wetter conditions are continuing from July into August with rainfall totals in the last two weeks across the state ranging from 1 to 6 plus inches. Some isolated areas in south-central Iowa received between 6 to 7 inches of rain alone over this last weekend. The biggest concerns coming in from fields across the state are more disease-related with sudden death syndrome (SDS) becoming more apparent in soybean fields across the state and southern rust in corn. ISU Extension and Outreach field agronomists share more specifics about what is happening in their respective regions across the state below.
Gentry Sorenson (Region 2):
Buena Vista, Clay, Dickinson, Emmet, Hancock, Kossuth, Palo Alto, Pocahontas, Winnebago counties
"Rainfall received across the area in the last week ranged from 0.5 inch to 3 inches. Due to rainfall over the last several weeks, ponding can be found in several low-lying areas. The corn growth stage ranges from R3 to R4, and the soybean growth stage is R4. Following the derecho on July 29, 2025, some areas have corn that is leaning from the high winds and have tattered leaves. Fall harvest in the affected fields could be slow due to the standability of the crop. Snap in corn fields that I visited were low and are typically above the ear. Spray planes continue with fungicide applications on corn fields. Phone calls consisted of questions on herbicide drift, soybean sudden death syndrome, and southern rust in corn.
Josh Michel (Region 5):
Allamakee, Buchanan, Clayton, Delaware, Dubuque, Fayette, Jones, Linn, Winneshiek counties
“Rainfall continued across most of the region last week with amounts generally ranging from 1 - 2 inches. Some isolated areas, however, received up to 3 inches. Over the past two weeks, some areas have received up to 6 inches of rainfall. As a result, some producers are having a difficult time completing oat harvest and getting the third crop of alfalfa finished up. That being said, I’d estimate that around 70-75% of the oats have been harvested so far. In general, most corn fields are at R3 (milk stage) to R4 (dough stage), while most soybeans are currently at R3 (beginning pod development) to R5 (beginning seed fill). Gray leaf spot and northern corn leaf blight pressure continue to slowly increase, while minor reports of tar spot and southern rust are starting to show up in some isolated areas. While soybean-related disease concerns remain low, reports of SDS and white mold are starting to show up in some isolated areas as well. Despite warm temperatures, many pastures continue to look good with the recent rainfall over the past couple weeks. The majority of field calls this past week centered around crop disease management and late season weed management.”
Meaghan Anderson (Region 7):
Boone, Dallas, Jasper, Madison, Marshall, Polk, Story, Tama, Warren counties
“Central Iowa has changed a lot in the past several weeks, with continued rainfall and both corn and soybean developing rapidly. Rainfall in the past two weeks in central Iowa has ranged from about 1.5 inches to over 6 inches; since July 1, a large bullseye over Dallas, Boone, Story, and some surrounding counties has received over 14 inches of rainfall. Corn is now mostly in the R4 (dough) or early R5 (dent) stage. Soybeans are in the R4 (full pod) or R5 (beginning seed) stage. Disease is the hottest topic of the last several weeks, with southern rust and SDS as common topics of conversation. It is almost time to head out to corn fields and do yield checks; during that time, I recommend evaluating the disease pressure in the canopy to compare hybrids, spray programs, or other factors that may be causing differences. Weeds continue to persist in fields and I’m still receiving a few calls about herbicide drift.”
Rebecca Vittetoe (Region 8):
Iowa, Jefferson, Keokuk, Poweshiek, Washington, Johnson counties
“Rainfall totals from Aug. 4 to Aug. 11 ranged from less than 0.1 inch to just over 1 inch in most areas across my region with some isolated areas receiving heavier amounts. Corn is mainly R3 to R5 and soybeans are mostly R4 to R5. The major issues or concerns seems to be disease related in both soybeans and corn. In soybeans, SDS is becoming more prevalent in fields, particularly in lower lying areas, wet spots, or more compacted areas in the field. On the corn side, there is a lot of buzz around southern rust. In general, it is more prevalent in the lower canopy, especially in fields that have been sprayed with a fungicide. However, depending upon if a fungicide was sprayed, when it was sprayed, and hybrid susceptibility, I am seeing it move up in the canopy. Other diseases I can also find in corn are tar spot, gray leaf spot, and northern corn leaf blight. The ample rain this growing season have kept forages and pastures looking good for this time of year. The biggest challenge has been on trying to get hay made in a timely fashion between rain events.”
Virgil Schmitt (Region 9):
Cedar, Clinton, Des Moines, Henry, Jackson, Lee, Louisa, Muscatine, Scott counties
"In the counties I cover, before the rains of Saturday night and Sunday morning, areas roughly north of I-80 received no rain and areas roughly south of I-80 received 0.25 inch or less of rain last week. Including the weekend rains, most of the area I cover received from 0.75 inch to nearly 4.0 inches of rain last week. Heavier amounts (5+ inches) occurred in some places. Generally, rainfall became heavier from south to north. Most corn is late R4-R5 and generally looks good. Low levels of many corn diseases continue to easily be found. Soybeans are mostly R5 and generally look good. Spots of SDS in soybean fields are appearing. Generally, they are scattered plants in the field or patches in low spots or compacted areas, such as field entrances, fall 2024 grain loading sites, etc. Forages continue to look good. Many people were able to finish hay harvest before the weekend rains. Calls last week mostly centered around fungicides and weed management.”
Logan McCrea (Region 11):
Appanoose, Davis, Lucas, Mahaska, Marion, Monroe, Van Buren, Wapello, Wayne counties
"The last week featured more precipitation, with the storms late last week bringing in varying amounts across the board but the heavier amounts coming in Appanoose and farther west into Lucas and Wayne counties. Isolated amounts near Mystic, Iowa came in the 6-7 inch range, leading to some flooding issues. Thankfully, for those areas, the storms that were predicted over the weekend did not end up bringing the high amounts of predicted rain, and the flooded areas can have some opportunity to dry out this week. Corn ranges from R3 to early R5, while soybeans also range from R3 to R5. SDS has really begun to show up in some soybean fields as well, with it being very noticeable from the road in some fields while others you can walk through and find a plant here or there showing symptoms. Southern rust continues to lead the charge in corn with lots of development in fields leading to questions regarding later fungicide applications. In general, it varies on a case-to-case basis depending on growth stage, disease severity, and plenty of other variables. Here is a link to the Crop Protection Network with all you need to know regarding southern rust, and as always, get out and scout and reach out to your local field agronomist for any questions you may have."
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- Field Agronomist in EC/SE Iowa