Regional Crop Update: June 29 - July 7, 2026

The hot and humid conditions last week really pushed the crops along. The week also brought heavy rainfall to parts of the state – including areas in central Iowa getting 12+ inches over a 3-day period. Corn fields are starting to tassel, and soybeans are fully in the reproductive stages now. Bacterial leaf streak, Goss’s wilt, weed escapes, Japanese beetles, and adult corn rootworm beetles emerging are some of the issues observed by ISU extension field agronomists this past week. Read on for more specific updates on what’s happening in fields around the state.  

Angie Rieck-Hinz (Region 3) 

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

“Corn ranges from late vegetative stages to VT. At this point in time, disease pressure remains fairly low, but I am seeing more and more Bacterial leaf streak, gray leaf spot, and some northern corn leaf blight. I have yet to find tar spot.  Our current weather conditions are providing enough humidity, but it’s been a bit too warm for tar spot. You can track tar spot by looking at  this map. Soybeans are R2, and I am sure there are R3 beans out there somewhere. Most post herbicide applications have finished. I have seen very little insect pressure in either crop, but the Japanese beetles are present, and you may find heavier feeding pressure on the outside rows of a soybean field. As we go into silking, watch for silk clipping. And as a reminder, spiking that fungicide (if needed) with an insecticide (cheap insurance) is not a good integrated pest management practice. We have so very few choices in insecticides, let’s not drive resistance by using insecticides when they are not needed. Below is a table from the Iowa Environmental Mesonet showing the precipitation totals and growing degree days from June 29, 2026, through July 6, 2026, for selected reporting stations across NC Iowa.”

Meaghan Anderson (Region 7)

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

“After asking nicely for rainfall last week, central Iowa was the bullseye of storms this past weekend, with some locations between Ankeny, Ames, and Maxwell receiving more than 12 inches of rainfall and many others receiving 5-10 inches. Many areas were underwater, though some are receding relatively quickly. Some corn was lodging after the storms came through; I’ve heard of some corn with greensnap as well, and hope that was limited. Corn is nearing tassel in many fields. Bacterial leaf streak (BLS), Goss’s wilt, and tar spot continue to be fairly regular finds, though they’re all at fairly low incidence. Soybeans are in the early reproductive stages now, with the earliest planted beans probably at R3. Japanese beetles are the most common insect I’m finding in soybean fields; defoliation has to be quite severe (20% of leaf area) to warrant an insecticide treatment, and I’ve seen no field anywhere near that. Asian copperleaf continues to thwart herbicide treatments and emerge with every rainfall in central Iowa. Conversations recently have been about herbicide injury, killing weeds, spraying fungicide, and other later season management topics.” 

Rebecca Vittetoe (Region 8)

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

“Over the last week, with the hot and humid conditions, you could almost watch the crops grow. Tassels are starting to appear in the earlier-planted corn fields, and I expect to see more fully tasseled fields by the end of this week. Most soybean fields are fully flowering (R2), and some fields are starting to set pods (R3). Bacterial leaf streak has been the most common disease in corn that I have seen or received photos of over the last week. However, with the recent weather conditions, keep an eye out for gray leaf spot. Japanese beetles are present, and I have started to see the first adult corn rootworm beetles emerging. Recent questions have focused primarily on herbicide injury and weed escapes, and I am starting to receive more questions about fungicide decisions.”

Virgil Schmitt (Region 9) 

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

“During the last week, the counties I cover have generally received less than 0.1 inch of rain near the Missouri border up to 2.5 inches along and north of I-80. There were two hail events, of which I am aware, and some wind damage to corn. Most corn fields are V16-V18 and look good. Some fields are at VT-R1. However, other fields continue showing nitrogen deficiency symptoms in poorly drained areas. Most soybeans are R2 and also look good except for areas where the soil is too wet. In those wet soils, soybean appearance has improved over the last week. Water hemp continues to be a major problem. Last week, many fields received post-emergence herbicide applications. Small grains and forages are also doing well. Some oat fields have completely turned color. A little second cutting of hay has been cut. Calls last week mostly centered around weed management, herbicide drift, and fungicide applications on corn.” 

Aaron Saeugling (Region 10) 

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

Hot weather has finally shown up in western and southwestern Iowa. With hot weather and variable precipitation over the Fourth of July weekend, crops are rapidly growing. Atlantic and north of Atlantic, drier conditions prevail, but south of Atlantic, wetter conditions are more common. Corn tassels are showing up, and soybeans are in full flower mode (R2) with early planted beans developing pods (R3). At this point, disease pressure is low with a few cases of bacterial leaf streak being reported. The other thing to scout for is Japanese beetle feeding in both corn and soybean. This will be a good week to scout corn for tar spot and other leaf diseases in corn before making fungicide applications. Pastures are still in good shape, but hot temperatures will slow cool season grass growth, especially where moisture is short. Putting up alfalfa hay can be challenging with showers and high humidity conditions. Keep in mind when baling hay over 75% humidity, the equilibrium moisture is unlikely to be below 20% — so be prepared for a few “hot” bales.

Logan McCrea (Region 11) 

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

“The past 7 days brought rainfall amounts mainly in the range of 0-1 inch, though a few localized areas had higher amounts in the 2-3 inch range. This bit of moisture, paired with the warm temperatures, led to some significant growth within fields, and there are now tassels beginning to pop through in many corn fields. Corn disease pressure is fairly low (low amounts of grey leaf spot and northern corn leaf blight), but will be something to monitor as many of our corn fields begin to move into their reproductive growth stages. Soybeans have flowers galore and are mainly in the R1-R2 growth stage. Weed control in soybeans is spotty, and there still have been lots of sprayers in fields working on cleaning up some larger than you would like waterhemp. Japanese beetles have really picked up in numbers over the past week or two. Pastures have slowed down a bit with the warmer weather, but overall still look good for the time of the year, and lots of hay has been put up in the past week with the drier weather.”

Madelynn Wuestenburg

Statewide weather update

The holiday weekend brought multiple rounds of storms and heavy rain across the state. Greatest accumulations occurred over central Iowa, with the largest 24-hour accumulation being 12.6 inches reported in Elkhart. Significant flash flooding impacted communities in Polk, Story, and Jasper counties. These storms also produced high winds and hail. This significant precipitation event puts central Iowa at 3-6.5 inches of rainfall above normal for the first week in July. More than the entire month’s worth of rain fell in two days for some locations in central Iowa. Soil moisture is sufficient, or more than sufficient, for much of the eastern half of the state. The western, northwestern, and north-central parts of the state have a few counties in moderate drought (D1) or are abnormally dry (D0) as reported on the U.S. Drought Monitor.