Regional Crop Update: July 21 - July 28, 2025

This July is rounding out to be one of the wettest July’s on record. Rainfall totals across the state ranged from just over 0.1 inch to  pockets across the state seeing more than 5+ inches for the week. Many of these areas were already dealing with already saturated conditions. The wet conditions, southern rust in corn, corn rootworm beetles, weed escapes, and SDS showing up in soybean fields were some of the hot topics the extension field agronomists came across this past week that. Read on for more specifics about what is happening in crop fields around the state.

Angie Rieck-Hinz (Region 3):

Cerro Gordo, Franklin, Hamilton, Hardin, Humboldt, Webster, Worth, Wright counties 

"Rain concerns and fungicide decisions continue to dominate the discussion across NC Iowa. For the period of July 20 through July 28 Northwood, Iowa saw 7.02 inches of rain, or 5.53 inches above average. Table 1 below shows rainfall amounts from July 1 through noon on July 28 for several NC Iowa locations. Corn is primarily R2 to R3 with a few fields beginning R4. After finally finding tar spot last week in Franklin County, I can now say I have seen all our major foliar diseases in corn. However, across all the fields I was in last week, the disease pressure is still low and everything was below the ear leaf. I think we all have concerns about southern rust of corn, but it was detected several weeks ago, and with the exception of susceptible hybrids, does not appear to have done much. I realize your situation may be different and that is why I am continuing to encourage you to scout!  Soybeans are R3 and I have even found a few R4 (full pod) fields. I admit, I have not found much disease pressure in soybeans. Other than Japanese beetle feeding (minor) on field edges, I have not found any aphids or other soybean insect pests that are causing concerns. Below are some crop disease and fungicide resources you may find helpful."

Crop Disease and Fungicide Resources

• Fungicide Efficacy for Control or Corn Foliar Diseases              
• Fungicide Efficacy for Control of Soybean Foliar Diseases
• Fungicide Efficacy Tool
• Corn Fungicide ROI Calculator
• Crop Diseases Forecasting Tools

Terry Basol (Region 4):

Benton, Black Hawk, Bremer, Butler, Chickasaw, Floyd, Grundy, Howard, Mitchell counties 

“Crops across my area continue to look good. Corn primarily ranges from VT to R2 and some early planted acres are at R3. Continue to scout corn for foliar diseases, as we remain to have favorable conditions for disease development, particularly gray leaf spot for the next week. Keep an eye out for southern rust, as there have been confirmed cases in NC Iowa, as well as other parts of the state. You can also track the progression of confirmed Iowa counties with Southern Rust. Soybeans range from R3 to R4. On average, soybean leaves look relatively clean with very low incidences of foliar disease development. Continue to scout and assess for frogeye leaf spot, downy mildew, white mold, and sudden death syndrome due to the higher rainfall that we’ve had over the past few weeks. Third cutting of hay has started in the area, but progression has been slowed considerably due to the amount of rainfall received this past week. Oat harvest has begun for the area but again has been hindered due to the rain. Just like much of the state, this area has received an ample amount of rainfall over the past couple of weeks. The NE Iowa Research and Demonstration Farm near Nashua, received 3.85 inches of rain in the last week, for the month of July has received 8.05 inches, and for the growing season (April 1- July 28, 2025) a total of 23.85 inches of rain.”  

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 0.50 to 2 inches. Some isolated areas, however, received up to 4.5 inches. This brings our July rainfall totals in some areas up to 10 to12 inches for the month. As a result, many producers are having a difficult time harvesting oats and getting the second crop of alfalfa finished up. That being said, I’d estimate that around 25% of the oats have been harvested so far and some producers are starting their third harvest of alfalfa. In general, most corn fields are at R2 (blister stage) to R3 (milk stage), while most soybeans are currently at R2 (full flower) to R3 (full pod development). Gray leaf spot and northern corn leaf blight pressure continues to slowly increase. While soybean-related disease concerns remain low, SDS may start showing up in some areas. 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 insect and crop disease management.”

Rebecca Vittetoe (Region 8):

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

“This last week continued the theme we’ve experienced all month of being wet. Rainfall totals across the counties I cover ranged from less than 0.5 inch to more than 3 inches. Corn ranges from the R2 (blister) to R4 (dough) stage, while soybean fields are mainly in the R3 to R4 stages. Southern rust and corn rootworm beetles were the hot topic areas I received questions on in corn this last week. If you haven't scouted, please continue to scout and monitor fields for southern rust. Additionally, I’ve noticed more western and northern adult corn rootworm beetles flying around this past week. In some fields I did observe silk clipping, but thankfully pollination was already complete. On the soybean side, lodging, downy mildew, SDS starting to show-up, and weed escapes were the main concerns I received.” 

Virgil Schmitt (Region 9):

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

“Most of the area I cover received from 2.0 inch to nearly 8.0 inches of rain last week. There was considerable low land flooding and ponding in many areas. Most corn is R2-R3 and generally looks good. Low levels of many corn diseases continue to easily be found, but I have not yet seen a field requiring a fungicide application. Soybeans are mostly R4 and generally look good. Minor insect (Japanese beetles and grasshoppers) feeding continues. There is little disease. Forages are doing well but harvest of some fields continues to be slowed by rain. Calls last week mostly centered around herbicide drift, fungicides, corn rootworms, and weed escapes.”

Aaron Saeugling (Region 10):

Adair, Adams, Cass, Clarke, Decatur, East Pottawattamie, Fremont, Mills, Montgomery, Page, Ringgold, Taylor, Union, West Pottawattamie counties 

“Hot weather and adequate rainfall are moving this crop along quickly with growing degree days around 1900, which is slightly behind the average and the past few years. However, the recent hot temperatures during both the daytime and nighttime are closing the gap rapidly. Corn is in the R2 (blister) to R4 (dough) stage, with possibly some early planted or maturity hybrids starting to reach R5 (dent). Kernels are accumulating starch at this point in the grain fill process, so excess water should translate heavy kernels. Continue to monitor corn fields for southern rust in corn and other disease development. Soybeans at this point are in the R2 to R4 stages, with pods developing in the upper portion of the canopy. With rapid growth, seed development is the next critical phase for soybeans, which should make use of the excessive rainfall if adequate nutrients are available. This is a great time to evaluate nodule development on your soybeans since we now at peak nitrogen uptake utilizing 3 to 4 pounds nitrogen/acre/ day. Be on the lookout for disease development like Sudden Death Syndrome (SDS). Pastures look great but continue weed control measures. For those who have grass hayfields this would be a great time to apply some nitrogen fertilizer and make and additional cutting this season.” 

Logan McCrea (Region 11):

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

“Over the past 7 days, plenty of precipitation has continued to fall across SC to SE Iowa, with totals ranging from around 2 inches all the way up to some reports of close to 8 inches over towards Van Buren County. The last spot of D1 drought around Ottumwa in Wapello County received anywhere from 2 to 6 inches of rain as well, so the minor drought conditions there should be removed soon. Lots of corn fields range from the R1 to R3 stage, and lots of soybeans are in the R2 to R4 stage. Soybean disease levels are very low, and corn has a plethora of diseases that can be found in fields although none appear at super high levels yet and seem to be hanging around the lower canopy as of now. Forages look tremendous given the heat and moisture that we have, but hay cutting has been a challenge with the frequency of rainfall that we are getting. Insect levels are relatively low, with some minor Japanese beetle feeding going on along field edges. Most calls over the past week have been regarding southern rust and fungicide application questions regarding it.”