Regional Update: July 10 – July 18, 2023

July 18, 2023 10:27 PM
Blog Post

Over the last week much needed rain was received, but it also unfortunately brought along wind and hail to some parts of the state. Other hot topics coming in from fields across the state this past week included corn rootworm, soybean gall midge, phytophthora in soybeans, tar spot, gray leaf spot, and weed control issues. Read on for more specifics about what Iowa State University Extension and Outreach Field Agronomists have seeing or had questions about around the state in the last week.  

Northwest Iowa

Leah Ten Napel (Region 1): “Northwest Iowa has received some much-needed moisture over the past two weeks, but with that has come some pockets of strong wind and hail damage. Most corn fields are in the VT to R1 stage and pollination is occurring. Soybean fields are staging R1 to R2. Pests that we are dealing with at this time are escaped weeds and insects like grasshoppers, soybean gall midge and corn rootworm. Little disease pressure is being seen at this time.”

Soybean gall midge has been causing more issues in some fields in Central Iowa. Pictured above are some third instar soybean gall midge larvae found in a Dallas County soybean field. Photo courtesy of Meaghan Anderson. 

North Central Iowa

Angie Rieck-Hinz (Region 3): “During the week of July 10 through July 17, nearly all reporting stations in my counties reported rainfall, although we all know how spotty the rainfall has been. Northwood, IA, which has been one of the drier areas finally received just over 4 inches of rain last week. The Hampton area continues to average about a 6.5-inch deficit in rain from April 10 through July 17. The majority of corn is at R1, but ranges from VT to R2.  Even though the number of counties reporting tar spot is on the rise, I totally admit, I am not finding much if anything in the fields I visit. It should also be noted that corn rootworm beetle pressure is highly variable. In a few corn fields I have been in it is difficult to find beetles and other fields beetles are easy to find. Join in at the corn rootworm management field day at the Northern Research Farm to learn how to assess damage and plan for next year. Soybeans are R2 to R3 on average. The biggest challenge with soybeans seems to be the edge-of-field feeders such as Japanese beetles and grasshoppers. I have not seen any locations warranting treatment, but I have had many phone calls about these insects. I have also seen phytophthora in soybeans.”

Phytophthora root and stem rot in soybean.  Photo courtesy of Angie Rieck-Hinz. 

Northeast Iowa

Josh Michel (Region 5): “Most of NE Iowa received some much-needed rainfall last week; however, some areas also received damaging winds and isolated hail. Generally, most of the area received at least 1 to 1.5 inches, but a few isolated areas received up to 3.5 inches. Fungicide applications are occurring as most corn fields are VT to R1. Corn rootworm management continues to be a topic of discussion as adults are being observed. Japanese beetles can also be found along most field edges. Soybeans are generally R1 to R3. Japanese beetles and grasshoppers continue to be the main leaf defoliators. Oats are beginning to be harvested for grain as approximately 80% of the fields have turned. Most of alfalfa second crop has been harvested, but farmers should continue to scout for potato leafhoppers. Recent rainfall may help some pastures, but growth will be slow due to warm temperatures. Field calls last week centered around fungicide applications and timing, soybean herbicide injuries, crop damage assessments, insect identification and management, and forage management."

Soybean field in Fayette County that had some hail damage. Photo courtesy of Josh Michel. 

Central Iowa

Meaghan Anderson (Region 7): “Central Iowa received a wide range of rainfall last week, ranging from close to 0.25 inches to over 4 inches. Tama County, and parts of Polk and Jasper counties remain drier than some other areas. Corn is fully into pollination in most fields now and some early-planted fields may be at R2 (blister) already. Fungicide applications are going on, but disease pressure remains very low. Tar spot is increasing in some fields but remains below the ear leaf in every field I’ve checked. Corn rootworm pressure continues to be a popular topic of conversation, with discussion this week turning to northerns with extended diapause in rotated corn. Soybeans are at R3 in many fields now. Waterhemp continues to persist in fields and will soon be above the canopy where it escaped POST sprays in soybean. Most recent phone calls have been about soybean gall midge, herbicide failures, and blister beetle in alfalfa.”

A tiny tar spot  found 33 leaves below the ear leaf in Boone County last week.
A tiny tar spot found three leaves below the ear leaf in Boone County last week. Photo courtesy of Meaghan Anderson. 

Southwest Iowa

Aaron Saeugling (Region 10): “Crop conditions in SW Iowa have improved with rainfall occurring in most parts of SW Iowa. With the rain, came some severe weather that brought high winds and hail causing pockets of crop damage to various degrees. Corn is in the VT to R3 stage depending on maturity and planting date. Isolated reports of corn disease indicate low incidence and extremely low severity of most corn diseases. Damp conditions may cause an increase of incidence of corn disease in the coming weeks. Aerial applications of corn fungicides have begun in sizable portion of SW Iowa. Soybeans have also benefited from recent rains. Soybean growth has vastly improved from 2 weeks ago and most soybeans have closed the row and weed control as of now looks good in most fields. Soybean gall midge reports are continuing to come in as well as other isolate pest calls. Soybean stages are in the mostly R1 to R3 stage. Forage and pasture conditions are benefiting from rainfall and cooler temperatures. Pond, stream and river levels are still at record lows indicating the need for additional moisture the rest of the growing season and significant rainfall at some point to replenish subsoil moisture levels.”

East Central, Southeast, and South-Central Iowa

Rebecca Vittetoe (Region 8): “This last week brought some more welcomed rain. Rainfall totals across EC Iowa were again variable ranging from a couple tenths to some isolated areas receiving closer to 2 inches. Unfortunately for some isolated areas, while the rain was welcomed, the wind and/or the hail was not. Corn mostly ranges from late vegetative to R2. Disease pressure remains low, but tar spot has been found in some fields in EC Iowa at low levels as well as some gray leaf spot. Corn rootworm pressure, especially in first year or rotated corn, along the Highway 30 corridor in my area has been the big topic of discussion. Soybeans are in the R1 to R3 stage. The main concerns in soybeans this last week have been insect defoliation (grasshoppers and Japanese beetles) and weed escapes. While the recent rains have helped some with forage growth, in general, growth continues to be slow and a concern for many producers.”  

Started seeing some small. gray leaf spot lesions lower in the crop canopy in corn fields this last week. Photo courtesy of Rebecca Vittetoe. 

Virgil Schmitt (Region 9): “Rainfall in the last week in the counties I cover ranged from less than 0.2 inch to 3 inches, with greater amounts generally north of Highway 92 and lesser amounts south of Highway 92. Rainfall continues to be very hit-and-miss. Many alfalfa fields have unmanaged populations of potato leafhoppers. Oats are starting to turn color as they mature. Most corn is V18 to R1 and generally looks good to excellent except in areas of coarse soils, clay soils, and compacted areas. Some fields have plants with dry, brown silks. Most soybeans are R2 and generally look good to excellent. Some fields will be at R3 by the end of the week. Phone calls, emails, and field visits last week mostly involved grasshoppers, corn rootworms, fungicide applications, insecticide applications, weed management, and herbicide injury.”


Clarabell Probasco (Region 11): “Over the past week, a few rain systems have moved across the region here and there, some becoming more spotty as they moved. Rainfall received totaled anywhere from a few tenths up to an inch. Combined with previous rainfall events, the US Drought Monitor made slight improvements in south central Iowa but many counties still have large areas classifying as a D3 drought with the vast majority that remains listed as a D2 drought. Corn fields are mainly at VT/R1 stages and in fields that I have been in, pollination is going well. Soybean fields are around the R2-R3 development stages. Disease pressure is low in both corn and soybean fields. Most field calls have been pertaining to Japanese beetles feeding on soybean foliage and corn silks. Additional information on scouting for Japanese beetles and understanding the thresholds associated with the pest can be found here.”

Japanese beetles haven been causing more defoliation in some soybean fields in SC Iowa.  Photo courtesy of Clarabell Probasco. 

Check out the map below to find your local ISU Extension field agronomist and find their contact information here.


Rebecca Vittetoe Field Agronomist in EC Iowa

Rebecca Vittetoe is an extension field agronomist in east central Iowa. Educational programs are available for farmers, agribusiness, pesticide applicators, and certified crop advisors.

Areas of expertise include agronomy, field crop production and management of corn, soybeans, and...