Regional Update: July 3 - July 10, 2023

Corn rootworm, soybean gall midge, tar spot, drought stress, and weed control issues are some of the common issues or questions Iowa State University Extension and Outreach Field Agronomists have seen or heard about the past couple of weeks. Read on for more specifics about what’s happening around the state. 

North Central Iowa

Angie Rieck-Hinz (Region 3): “For the most part crops in NC Iowa are looking good, but continued rain will be needed to sustain development and fill grain. Corn is from late vegetative stages to R1. I have been scouting for corn diseases and have yet to find anything- which means I just jinxed myself.  I have been receiving a lot of phone calls about rootworm damage in first year corn after beans. Soybeans are R1 to R2, and I admit, finally looking like they are growing. So far, insect pressure has been non-existent except for scattered pockets of Japanese beetle feeding on soybeans.  Grasshoppers continue to increase in population along field edges.” 

Northeast Iowa

Terry Basol (Region 4): “Crops continue to push through despite a dry growing season in NE Iowa. Corn is at the VT/R1 stage or very close to it across the area, depending on planting date. Continue to scout for corn rootworm activity to determine if management strategies need to be changed in the future So far, upper canopy leaves (ear leaf and above) have been pretty clean of foliar diseases (including tar spot) but continue to scout and monitor. Read more about how environmental conditions favor the development of the most common foliar diseases here. We are still seeing some leaf rolling for corn that’s planted in fields with lighter soils due to dry conditions. Soybeans are flowering and range from R1 to R2 stage for the area. Continue to scout for insect activity. Watch for grasshoppers and spider mites amid our drier conditions. For the last couple of weeks, we’ve seen a favorable change in weather patterns for NE Iowa, and have been able to receive some rain events that have been very well needed for the crops. Rainfall amounts range from about 0.5 inch up to 4.0 inches in an isolated area of Bremer County according to the National Weather Service.  According to the Iowa Mesonet, the NE IA Research and Demonstration Farm here at Nashua received 0.79 inch of rain for the period of June 26 – July 10." 

Josh Michel (Region 5): “Most of NE Iowa received some much-needed rainfall over the past couple weeks. Generally, most of the area received 1.5 to 2 inches, but a few isolated areas were able to receive up to 2.5 inches. This was welcomed as many crops continue showing signs of moisture stress. Most corn fields are quickly approaching tasseling as many fungicide applications are beginning to occur. Japanese beetles are beginning to show up and corn rootworm management has also been a topic of discussion. Soybeans are generally around R1 to R2. Japanese beetles and grasshoppers continue to be found in most fields. Lingering herbicide injuries and weed escapes, especially on 30-inch rows, have also been recent concerns. Most of second crop alfalfa has been harvested, but scouting should continue for potato leafhoppers. While the rain may promote some growth, most pastures across the region have significantly slowed down due to warming temperatures. Other field calls for the week centered around fungicide applications, herbicide injuries, weed identification and management, forage management, as well as crop assessments related to the drought.”

Central Iowa

Meaghan Anderson (Region 7): “Some corn has started pollinating and much of the corn is nearly there in central Iowa after a cool week last week. The difference in tasseling and silking across fields is a clear visual to the variability in corn fields this summer. Grey leaf spot and tar spot are beginning to show up with only a few lesions in the low part of the canopy; they’re still quite difficult to find in most fields. Corn rootworm beetles are emerging and some corn fields have suffered a lot of root feeding this summer; if you haven’t dug some roots yet, especially in continuous corn fields, now is the time to do it. Waterhemp remains prevalent under many corn canopies and will need to be noted for next year as the population density will be larger in those fields. Soybeans are mostly R1-R2, but there are some fields at R3 already. Narrow rows are closing, but herbicide issues continue in fields with poor control, off-target movement, and even carryover still being identified. Soybean gall midge is making its presence known in the far western reaches of central Iowa this summer; make sure to check stands closely if you notice plants wilting along field edges as it may be this insect pest!”

Southwest Iowa

Aaron Saeugling (Region 10): “Crop conditions in SW Iowa have improved in the past 2 weeks due to receiving some needed precipitation. Some locations on June 29th received heavy winds causing lodged corn in portions of Cass, Pottawattamie, Montgomery, and Fremont counties. Corn is now in the VT to R1 stage and looks better than in previous weeks. Of special note this year is uneven tassel emergence. Little disease severity has been noticed at this point in the growing season. Soybean have started to close the canopy and are getting taller due to recent rains. First applications of weed control have been applied and in general look good so far. Second cutting alfalfa has been baled and yields were less than average in areas with dry conditions. Insect pressure being reported includes potato leafhoppers, grasshoppers, Japanese beetles, and soybean gall midge. With crops now requiring 0.22 to 0.30 inch of moisture per day, we will see how long crops can hang in there without additional moisture.”

East Central, Southeast, and South-Central Iowa

Rebecca Vittetoe (Region 8): “While EC Iowa received some much-needed rainfall over the last two weeks, most areas are still 5 to 8 inches below normal rainfall for the growing season. Corn is mainly in the late vegetative stages to VT/R1. We are seeing the unevenness in corn fields appear again with a lot of uneven tassel emergence. Concerns or issues being noted in corn fields include corn rootworm feeding on corn roots, especially in first year corn and tar spot (Poweshiek, Marion and Mahaska counties) at low levels. Soybeans are mainly at the R2 stage and finally look like they have grown some. The main concerns in soybeans have been herbicide injury, issues with weed control, and defoliation from insects (mainly grasshoppers and Japanese beetles). While soybean gall midge has not been found in EC Iowa, it is again being noted in soybean fields to the west of us and is a pest to keep your eyes out for. Most folks have wrapped up second cutting of hay, and in general forage growth has been very limited with the drier conditions.”

Virgil Schmitt (Region 9): “Rainfall in the last two weeks in the counties I cover ranged from less than 0.05 inch to over 5 inches, with greater amounts generally south of Highway 92 and lesser amounts north of Highway 92. Rainfall continues to be very hit-and-miss. Second cutting hay is basically wrapped up. Most corn is V15 to R1 and generally looks good to excellent except in areas of coarse soils, clay soils, and compacted areas. Tassel emergence is very uneven in many fields. Most soybeans are at R2 and generally looks good to excellent. Phone calls, emails, and field visits last week mostly involved spider mites, Japanese beetles, grasshoppers, corn rootworms, fungicide applications, slow or lack of performance of Enlist.”

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