Most corn fields across the state are getting into the R2 to R3 stage and soybeans are in the R2 to R4 stage. Some of the more common issues or observations ISU Extension field agronomists made or received about fields across the state this last week included diseases like rust in corn or white mold and SDS in soybeans, Japanese beetles, corn rootworm, soybean gall midge, and recent damage due to storms early this week. Read on for more specifics about what’s happening in different areas across the state.
Northwest Iowa
Leah Ten Napel (Region 1): “Rainfall across the region has varied 0.5 – 2.0+ inches this past week. Corn is VT-R3 in most areas, but there is a lot of in-field variability. Soybeans are R2-R3. Diseases being seen in corn are common rust and Physoderma. Little disease has been reported in soybeans at this time. However, growers should continue to scout for disease as weather conditions have been conducive to the development of certain diseases in both corn and soybeans. Japanese beetles are the insect pests being reported at this time, but other insect pressure is relatively low. Recent storms have included strong winds that may have brought damage to crops. If you had impacted fields it is best to wait a few days after storms to evaluate damage, and contact crop insurance.”
Gentry Sorenson (Region 2) “Rainfall over the past week has been light, around 0.5 inch in some areas, and we received some recent rain in varying levels. Disease pressure in corn has been low, mainly common rust observed at low levels. Corn growth stage is R2 and the soybean growth stage is R3. Alfalfa fields were recently cut due to the drier weather and oat harvest operations were ongoing last week as well. Phone calls were primarily focused on fungicide applications. In-person conversations and concerns were regarding rainfall over the current growing season.”
Northeast Iowa
Josh Michel (Region 5): “Last week farmers were able to take advantage of nice stretch of dry weather to finish up any remaining oat harvests and work on their third crop of alfalfa across most of the region. While some isolated showers came through the area, precipitation amounts generally ranged from 0.10 inches, up to 0.50 inches of rainfall. Earlier-planted corn is mostly around R2 to R3, while later-planted corn fields have started tasseling. Fungicide applications are occurring in some areas even though disease pressure remains low. Japanese beetles and corn rootworm adults can be found in most fields that are still silking, but generally have been below threshold limits. Soybeans across the region are mostly R3 to R4. Japanese beetles continue to be found in most fields but have been below threshold limits. Many weeds, in particular waterhemp, are doing well in soybean fields that had pre-existing herbicide control issues earlier this year. Most of the field calls last week centered around crop disease assessments and management, insect management, and possible herbicide damage to corn and soybeans.”
Central Iowa
Meaghan Anderson (Region 7): “Parts of central Iowa received a deluge of rainfall in the past 7 days, with some areas receiving over four to five inches of rainfall. Corn is mostly in the R3-R4 growth stage and remains relatively clean in the canopy. Soybeans are also in the R3-R4 growth stage and some disease pressure is beginning to become more noticeable in fields, though pressure remains low overall. The biggest thing of note was finding white mold in a Boone County soybean field. I’ve noticed soybean start to lodge in some fields as a result of the recent rain. Questions about disease management have dropped substantially in the last week, though I’ve gotten more questions about soybean gall midge and weed pressure in both corn and soybean.”
East Central, Southeast, and South-Central Iowa
Rebecca Vittetoe (Region 8): “Over the last week and into early this week, my region has received anywhere from just over 1 inch to 3.5+ inches of rain. Some isoloated areas in Mahaska County had over 6 inches of rain. Unfortunately, some areas had some wind and/or hail damage early this week as well. Corn is mostly R2 to R4 and soybeans are mostly R3 to R4. Overall, disease pressure remains relatively low, but I can find rust (common and southern), gray leaf spot, northern corn leaf blight, bacterial leaf streak, and tar spot in corn fields. It's easier for me to find disease in earlier planted fields, but in general pressure is low. In soybeans I’ve seen and have heard more about SDS showing up in the last week and have also heard of white mold too. Corn rootworm beetles are quite prevalent in some fields, and I’ve also started seeing a few aphids in corn fields this last week.”
Virgil Schmitt (Region 9): “Rainfall during the last week in the counties I cover was from less than 0.1 to over 1.5 inches. This does not include Sunday night – Monday morning (July 28 – 29, 2024) rainfall amounts. Most corn is Late R1 to R2 and looks good. There is probably some R3 corn, but I have not seen any. Most soybeans are at R4 to R5 and also look good. All crops continue to have few disease or insect issues except potato leafhoppers continue to be above threshold in many alfalfa fields. Contacts last week mostly involved fungicides for both corn and soybean and herbicide drift, and there was one herbicide carryover field visit.”
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- Field Agronomist in EC/SE Iowa