Regional Crop Update: June 30 - July 8, 2025

Tassels started showing in cornfields across the state, while soybean fields are flowering and some are starting to set pods. ISU Extension field agronomists reported a range of concerns and observations over the past week, including potential herbicide failures, low levels of foliar diseases such as gray leaf spot, tar spot, and northern corn leaf blight, rootworm injury, and soybean gall midge being found in two new counties. Below, field agronomists share more details about what they’re seeing in their respective regions.

Leah Ten Napel (Region 1):

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

“Corn and soybeans across northwest Iowa are coming along very nicely. Most soybeans are at the R1-R2 stage. Corn fields in the area are getting close to or beginning to tassel. Hay and pasture fields have been very productive with adequate rainfall. Disease and insect calls have been low. Weed pest are causing the most issues with drift calls and herbicide fails. As crops begin to enter the reproductive stages, applying fungicides becomes a big conversation. Take time to read this ICM blog titled “Before You Pull the Trigger: 2025 Fungicide Smarts for Corn” to help make your input decisions this growing season!”

Angie Rieck-Hinz (Region 3):

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

“For the week of June 30 through July 7 we continued to receive precipitation that ranged from a few tenths to several inches over the counties I cover.  Some localized areas in Webster and Hamilton counties received nearly 7 inches from storm that passed through on Saturday, July 5^th.  Corn ranges from late vegetative stages to R1 and soybeans from R2 to R3. The primary concern in corn is do we have enough nitrogen in some fields (see photo) where we have had excess rainfall? If we apply N will it help the corn or is the corn suffering more from lack of oxygen and is short and stunted because of that?  It is highly likely we have moved nitrate with leaching, but how far has it moved? Can corn roots still access it?  It is also highly likely we are losing N due to denitrification on daily basis in those ponded/saturated areas in fields.  While we have tools, such as N FACT to help us predict nitrogen rates needed under specific conditions, we do not have any tools that can adequately predict N loss or N needs in a rescue type scenario. On top of that, we recognize the extreme amount of scrutiny farmers are receiving based on messaging regarding nitrate removal for drinking water systems.  Other considerations include do you have access to high-clearance equipment or, can you have N flown on?  There are many moving pieces and there are no easy answers.  If you choose to apply N at this point in time, I suggest you limit application to 25-40 lbs per acre or even try different rates in that range across a field.  If possible, always leave a strip or two where you didn’t apply any additional N.  Set up your own trial so you can combine those strips independently to evaluate if the additional N provided a yield response or not.  While this information will not lend to decisions for the 2025 growing season, this information will help you make better informed decisions in the future when you experience another wet June. Most of my phone calls this week have been about fungicide needs, N concerns and herbicide drift.”

Meaghan Anderson (Region 7):

Boone, Dallas, Jasper, Madison, Marshall, Polk, Story, Tama, Warren counties 

“Central Iowa received a break from the rain last week, until this weekend and early this week where much of central Iowa received between 0.5 and 2 inches, with a few areas receiving higher amounts. The break in rain earlier last week appeared to be enough to get a lot of hay put up in central Iowa. Many corn fields are tasseling or at R1 (silking) stage and soybeans are at R2 or even R3 in some fields. Corn fields I’ve been in have relatively low insect pressure (so far!) and I can find a lot of foliar diseases but at very low levels. Both western and northern corn rootworm beetles have begun emerging in corn. Japanese beetles are apparent in soybean fields, but the damage hasn’t reached anywhere near threshold levels in fields I’ve walked. I have heard from numerous farmers that their corn crop looks as good as any corn crop, they’ve ever had so far this year. In the wet areas, corn and beans have both kept a kind of sickly yellow green color that has resulted in a few questions from farmers. Most issues still seem to relate to herbicides – issues with mixing, application, poor control, drift, you name it. I’ve had a handful of messages about corn rootworm feeding concerns and some questions about fungicide applications/disease pressure. Keep an eye out for corn rootworm pressure as the beetles emerge, tar spot and gray leaf spot in corn, and soybean gall midge – it was found as far east as Poweshiek and Tama Counties this week!”

Rebecca Vittetoe (Region 8):

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

“Over the Fourth of July weekend, rainfall totals ranged from about 1 to over 3 inches across the counties I cover. With the rain, came some wind that resulted in some damage to cornfields, more so in eastern Keokuk County. Some fields had willowing or leaning corn, and a few fields had plants that were root lodge. Corn started to tassel last week, and some fields are also silking (R1). Soybeans fields range from R1 to R3. Overall, both corn and soybean fields look pretty good in this part of the state. There was also a lot of second cutting hay put up this last week. Most concerns have been on foliar disease pressure and fungicide decisions in corn as well as rootworm injury, including some in first-year corn. I have been able to find very low levels of foliar diseases starting in some fields including the start of some gray leaf spot and have had reports of tar spot and northern corn leaf blight. Japanese beetles can be spotted, and I did see my first adult corn rootworm beetle over the weekend. Additionally, soybean gall midge was identified in Poweshiek County.”  

Virgil Schmitt (Region 9):

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

“Most of the area I cover received 0.2 to 1.5 inch of rain last week except there was a localized 2.0+ inch rain total in Cedar County.  Most corn is V13 to V15 and generally looks good. Many fields began to display tassels last week. Soybeans are mostly R2 and generally look good. Japanese beetles became evident in many soybean fields last week. Many fields of hay were cut last week. I was told by a few farmers that they had never baled such high-quality hay. Potato leafhopper injury is evident in many fields that have not yet been mowed. Calls last week mostly centered around weed management and herbicide drift.”

Logan McCrea (Region 11):

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

“The past week brought plenty of rainfall, with amounts over the weekend coming in around 4-5 inches in the Pella area, 2-3 inches closer to the Iowa/Missouri border, and variable amounts in between those two. Lots of corn fields are tasseled out and look to have favorable weather/plenty of moisture for their pollination window. Soybeans continue to chug along with post applications wrapping up finally and plenty of flowers out in fields. Poor drainage areas in fields are showing with the precipitation patterns the past few weeks and wouldn't mind some good drying weather. With the better weather during the week, plenty of grass and alfalfa hay got put up before the holiday and on the holiday. Insect wise, Japanese beetles are out and about causing plenty of trouble with trees and other home area plants but haven't caused too much trouble in ag fields yet. Calls over the past week have mostly been around fungicide decisions and late herbicide application questions.”