Regional Crop Update: July 6 - July 14, 2026

Corn fields around the state, if not tasseling currently, will be soon. Soybeans are mostly in the R2 to R3 stages. Overall, disease pressure remains low with reports of gray leaf spot and bacterial leaf streak being found in corn and bacterial blight, septoria brown spot and phytophthora being found in soybeans. Insects reported include Japanese beetles, grasshoppers, and corn rootworm beetles. Read on for more specific on what ISU Extension field agronomists are hearing and seeing in fields around the state. 

Leah Ten Napel (Region 1)

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

“Many corn fields across the region are R1. Fields are tasseling relatively evenly, but there are some exceptions to that. Bean fields are R2 to R3 and are looking healthy and relatively weed free. Calls this week have been on herbicide damage and fungicide decisions. Disease and insect pressure have been relatively low, but scouting each fields at this time is key. Some hybrids could me more or less susceptible to disease, and some fields will have different conditions and histories. Make fungicide and insecticide decisions based on your field conditions for the benefit of your cost of production and the longevity of the products. Crops seem to be handling high temperatures well at this time, but some additional precipitation in this corner of the state would be beneficial.”

Gentry Sorenson (Region 2)

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

"With warmer conditions the crops have been moving ahead rapidly. Tassels are present in many fields, but not all fields are tasseling currently. Later maturity hybrids or later planted corn will be tasseling in the next few days. Rainfall has been light over the past week, with less than an inch of rainfall across the area. Most soybeans were flowering and in the R2 to R3 growth stage. Control of waterhemp has been a common question and there have been several questions on fungicide applications."

 Angie Rieck-Hinz (Region 3)

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

“Corn is very late vegetative stages to R1. Disease pressure remains at low severity and low incidence. My college Gentry Sorenson and I took a tour of Alison Robertson’s Cardinal Fungicide Trial at the Northern Research Farm on July 13, (no treatments applied), and we found one tiny gray leaf spot lesion, two northern corn leaf blight lesions, and some common rust, none of which would warrant concern. Subsequently, I looked at two cornfields later that afternoon and found no disease. I have also been seeing both northern and western corn rootworm beetles. In fields north of Hwy 3, you will find potassium deficiency on lower corn leaves due to dry soils. In most cases, this is due to lack of soil moisture to move K into the plant, not due to low soil tests. Recent rains should help alleviate this problem. Soybeans are R2 to R3. Last week I was seeing a very slight increase in numbers of thistle caterpillars, and the Japanese beetle feeding along field edges has increased. Remember, in R stage soybeans you need 20% defoliation to consider a treatment (this is slightly different than what the Crop Protection Network states). You can use this tool, developed by Crop Protection Network to help calibrate your sight for defoliation: Soybean Insect Defoliation Training. Remember 20% defoliation is across the entire plant.  Patches of Phytophthora are showing up in soybean fields in low, or wet spots.”

Meaghan Anderson (Region 7)

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

“Most of central Iowa only received a small amount of rainfall last week following the deluge ahead of the Fourth of July. Parts of northern Boone County received more than 2-3 inches. Corn made a big jump from just barely showing tassels to probably nearing 50% silking. This occurs just as we head into a forecast of nothing by hot and dry for the next week or more. Disease pressure is quite low compared to what I remember at this point last year. It is almost impossible to find tar spot and most foliar disease is not treatable with fungicide (bacterial leaf streak). Both northern and western corn rootworm beetles are emerging in fields. Soybeans are in the R2-R3 growth stage, and aside from weeds continuing to emerge or regrow following herbicide applications, there isn’t much to be seen in fields. Bacterial blight is the most common disease, Japanese beetles and thistle caterpillars are present but not at high levels, and I’ve seen a handful of plants affected by Phytophthora root rot. Most phone calls have been about fungicide applications, disease questions, and weed management.”

Rebecca Vittetoe (Region 8)

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

“Last week was a relatively dry week; however, some areas did catch rain late in the week with totals ranging from 0.1 to just over 1 inch. Corn fields range from late vegetative to VT/R1. Soybeans are mostly R2 to R3. Corn rootworm beetles can be found in fields as well as Japanese beetles and grasshoppers. Now is a great time to dig and evaluate corn roots for rootworm feeding. So far disease pressure remains low in both corn and soybean fields. In corn, I can find bacterial leaf streak and a little gray leaf spot lower in the canopy. I have also seen one northern corn leaf blight lesion and one tar spot lesion, both lower in the canopy. Additionally, with the warmer temperatures I don’t expect either of those diseases to do much. Gray leaf spot is one to keep on your radar. Southern rust has been a topic of concern, but as of July 14, it hasn’t been identified yet in Iowa. In soybeans besides septoria brown spot and bacterial blight, I’ve just seen some Phytophthora. Weed control or lack thereof, especially with waterhemp, has also been a topic of discussion.” 

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 0.5 inch of rain north of I-80 and up to about 1.5 inch in places south of I-80. Most corn fields are V19 to VT/R1, with variation within some fields. Some fields have silks turning brown. Little disease is present. Most soybeans are R2 and look good. Small grains and forages also are doing well. Some oats hay is being made, and some oats fields have completely turned color. Second cutting hay should be mostly complete by the week’s end. Western corn rootworm beetles are showing up, Katydids are starting to sing, grasshoppers nymphs are present, and green foxtail is heading out. Calls last week mostly centered around herbicide drift, tank contamination, herbicide carryover, 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 

“Crop conditions look good in most portions of western and southwest Iowa. Dry conditions persist in Harrison, Crawford, Carroll, Shelby, Audubon, Pottawattamie and Cass counties. Corn is in the late vegetative to R2 phase, with early corn fungicide applications underway. Corn disease pressure currently is low to very low with some bacterial leaf streak, northern corn leaf blight and gray leaf spot visible. With the current warm forecast this week, continue to look for more gray leaf spot appearing. Insect pressure across the region is mostly low with hot pockets of Japanese beetles and western bean cutworm being most active. Soybean herbicide applications are wrapping up except for replant or later planted soybean. Early planted soybeans are in the R3 stage and others soybeans are not far behind. Isolated thistle caterpillars have been found, so keep watch for them as the season continues.”